From 8e85fadff28988f036182cc9345dae124ce7cd17 Mon Sep 17 00:00:00 2001
From: Ashley Whetter <ashley@awhetter.co.uk>
Date: Sat, 27 Jun 2020 18:33:20 -0700
Subject: [PATCH 01/73] Render `py::none` as `None` in docstrings

Closes #2270
---
 include/pybind11/cast.h | 1 +
 tests/test_pytypes.cpp  | 5 +++++
 tests/test_pytypes.py   | 5 +++++
 3 files changed, 11 insertions(+)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index be4f66b062..28283da8f3 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1609,6 +1609,7 @@ template <> struct handle_type_name<bytes> { static constexpr auto name = _(PYBI
 template <> struct handle_type_name<int_> { static constexpr auto name = _("int"); };
 template <> struct handle_type_name<iterable> { static constexpr auto name = _("Iterable"); };
 template <> struct handle_type_name<iterator> { static constexpr auto name = _("Iterator"); };
+template <> struct handle_type_name<none> { static constexpr auto name = _("None"); };
 template <> struct handle_type_name<args> { static constexpr auto name = _("*args"); };
 template <> struct handle_type_name<kwargs> { static constexpr auto name = _("**kwargs"); };
 
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index e70ffae9e6..f0d86d872c 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -32,6 +32,11 @@ TEST_SUBMODULE(pytypes, m) {
         for (auto item : list)
             py::print("list item {}: {}"_s.format(index++, item));
     });
+    // test_none
+    m.def("get_none", []{return py::none();});
+    m.def("print_none", [](py::none none) {
+        py::print("none: {}"_s.format(none));
+    });
 
     // test_set
     m.def("get_set", []() {
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index d6223b9ba8..79bee87750 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -37,6 +37,11 @@ def test_list(capture, doc):
     assert doc(m.print_list) == "print_list(arg0: list) -> None"
 
 
+def test_none(capture, doc):
+    assert doc(m.get_none) == "get_none() -> None"
+    assert doc(m.print_none) == "print_none(arg0: None) -> None"
+
+
 def test_set(capture, doc):
     s = m.get_set()
     assert s == {"key1", "key2", "key3"}

From a3daf87d45eb5a26c12ec44b7878f81e1dc8b8d5 Mon Sep 17 00:00:00 2001
From: fatvlady <fatvlad.95@gmail.com>
Date: Sat, 14 Mar 2020 15:15:12 +0200
Subject: [PATCH 02/73] Add failing optional test

---
 tests/test_stl.cpp | 40 ++++++++++++++++++++++++++++++++++++++++
 tests/test_stl.py  | 10 ++++++++++
 2 files changed, 50 insertions(+)

diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 207c9fb2bf..4c5ed853ab 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -50,6 +50,17 @@ namespace std {
 }
 
 
+template <template <typename> typename OptionalImpl, typename T>
+struct OptionalHolder
+{
+    OptionalHolder() = default;
+    bool member_initialized() const {
+        return member && member->initialized;
+    }
+    OptionalImpl<T> member = T{};
+};
+
+
 TEST_SUBMODULE(stl, m) {
     // test_vector
     m.def("cast_vector", []() { return std::vector<int>{1}; });
@@ -154,6 +165,23 @@ TEST_SUBMODULE(stl, m) {
         .def(py::init<>())
         .def(py::init<int>());
 
+
+    struct MoveOutDetector
+    {
+        MoveOutDetector() = default;
+        MoveOutDetector(const MoveOutDetector&) = default;
+        MoveOutDetector(MoveOutDetector&& other) noexcept
+         : initialized(other.initialized) {
+            // steal underlying resource
+            other.initialized = false;
+        }
+        bool initialized = true;
+    };
+    py::class_<MoveOutDetector>(m, "MoveOutDetector", "Class with move tracking")
+        .def(py::init<>())
+        .def_readonly("initialized", &MoveOutDetector::initialized);
+
+
 #ifdef PYBIND11_HAS_OPTIONAL
     // test_optional
     m.attr("has_optional") = true;
@@ -175,6 +203,12 @@ TEST_SUBMODULE(stl, m) {
 
     m.def("nodefer_none_optional", [](std::optional<int>) { return true; });
     m.def("nodefer_none_optional", [](py::none) { return false; });
+
+    using opt_holder = OptionalHolder<std::optional, MoveOutDetector>;
+    py::class_<opt_holder>(m, "OptionalHolder", "Class with optional member")
+        .def(py::init<>())
+        .def_readonly("member", &opt_holder::member)
+        .def("member_initialized", &opt_holder::member_initialized);
 #endif
 
 #ifdef PYBIND11_HAS_EXP_OPTIONAL
@@ -195,6 +229,12 @@ TEST_SUBMODULE(stl, m) {
     m.def("test_no_assign_exp", [](const exp_opt_no_assign &x) {
         return x ? x->value : 42;
     }, py::arg_v("x", std::experimental::nullopt, "None"));
+
+    using opt_exp_holder = OptionalHolder<std::experimental::optional, MoveOutDetector>;
+    py::class_<opt_exp_holder>(m, "OptionalExpHolder", "Class with optional member")
+        .def(py::init<>())
+        .def_readonly("member", &opt_exp_holder::member)
+        .def("member_initialized", &opt_exp_holder::member_initialized);
 #endif
 
 #ifdef PYBIND11_HAS_VARIANT
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 2335cb9fdf..613796356f 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -127,6 +127,11 @@ def test_optional():
 
     assert m.nodefer_none_optional(None)
 
+    holder = m.OptionalHolder()
+    mvalue = holder.member
+    assert mvalue.initialized
+    assert holder.member_initialized()
+
 
 @pytest.mark.skipif(not hasattr(m, "has_exp_optional"), reason='no <experimental/optional>')
 def test_exp_optional():
@@ -148,6 +153,11 @@ def test_exp_optional():
     assert m.test_no_assign_exp(m.NoAssign(43)) == 43
     pytest.raises(TypeError, m.test_no_assign_exp, 43)
 
+    holder = m.OptionalExpHolder()
+    mvalue = holder.member
+    assert mvalue.initialized
+    assert holder.member_initialized()
+
 
 @pytest.mark.skipif(not hasattr(m, "load_variant"), reason='no <variant>')
 def test_variant(doc):

From 556277d689f64f2b4910f5ace1ed1cb5a793726c Mon Sep 17 00:00:00 2001
From: fatvlady <fatvlad.95@gmail.com>
Date: Sat, 14 Mar 2020 15:20:04 +0200
Subject: [PATCH 03/73] Fix optional dereference type deduction

---
 include/pybind11/stl.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 32f8d294ac..77da133628 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -266,7 +266,8 @@ template<typename T> struct optional_caster {
     static handle cast(T_ &&src, return_value_policy policy, handle parent) {
         if (!src)
             return none().inc_ref();
-        policy = return_value_policy_override<typename T::value_type>::policy(policy);
+        using dereference_type = decltype(*std::forward<T_>(src));
+        policy = return_value_policy_override<dereference_type>::policy(policy);
         return value_conv::cast(*std::forward<T_>(src), policy, parent);
     }
 

From 8c06b9549255fccb5565578078223c992b061c27 Mon Sep 17 00:00:00 2001
From: fatvlady <fatvlad.95@gmail.com>
Date: Sat, 14 Mar 2020 16:10:14 +0200
Subject: [PATCH 04/73] Fix compile error on GCC4.8

---
 tests/test_stl.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_stl.cpp b/tests/test_stl.cpp
index 4c5ed853ab..928635788e 100644
--- a/tests/test_stl.cpp
+++ b/tests/test_stl.cpp
@@ -50,7 +50,7 @@ namespace std {
 }
 
 
-template <template <typename> typename OptionalImpl, typename T>
+template <template <typename> class OptionalImpl, typename T>
 struct OptionalHolder
 {
     OptionalHolder() = default;

From f99ff736c27f2209b66ca367b6ebe14c58c771f3 Mon Sep 17 00:00:00 2001
From: fatvlady <fatvlad.95@gmail.com>
Date: Mon, 29 Jun 2020 20:52:35 +0300
Subject: [PATCH 05/73] Add additional check to be more compliant with other
 casters

---
 include/pybind11/stl.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index 77da133628..b5f7e723f4 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -266,8 +266,9 @@ template<typename T> struct optional_caster {
     static handle cast(T_ &&src, return_value_policy policy, handle parent) {
         if (!src)
             return none().inc_ref();
-        using dereference_type = decltype(*std::forward<T_>(src));
-        policy = return_value_policy_override<dereference_type>::policy(policy);
+        if (!std::is_lvalue_reference<T>::value) {
+            policy = return_value_policy_override<T>::policy(policy);
+        }
         return value_conv::cast(*std::forward<T_>(src), policy, parent);
     }
 

From ae2ee2a4a51914cf78deb5c253a3b03cbb53ce72 Mon Sep 17 00:00:00 2001
From: Boris Staletic <boris.staletic@gmail.com>
Date: Mon, 15 Jun 2020 19:36:43 +0200
Subject: [PATCH 06/73] Avoid using deprecated API in python 3.9

The PyEval_InitThreads() and PyEval_ThreadsInitialized() functions are
now deprecated and will be removed in Python 3.11. Calling
PyEval_InitThreads() now does nothing. The GIL is initialized by
Py_Initialize() since Python 3.7.
---
 include/pybind11/detail/internals.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 6224dfb226..166a18a32f 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -273,7 +273,10 @@ PYBIND11_NOINLINE inline internals &get_internals() {
         auto *&internals_ptr = *internals_pp;
         internals_ptr = new internals();
 #if defined(WITH_THREAD)
-        PyEval_InitThreads();
+
+        #if PY_VERSION_HEX < 0x03090000
+                PyEval_InitThreads();
+        #endif
         PyThreadState *tstate = PyThreadState_Get();
         #if PY_VERSION_HEX >= 0x03070000
             internals_ptr->tstate = PyThread_tss_alloc();

From 714424387fffff17c8c18b6bf377fb3d47577791 Mon Sep 17 00:00:00 2001
From: B Krishna Chaitanya <bkchaitan94@gmail.com>
Date: Sun, 21 Jun 2020 17:23:53 +0530
Subject: [PATCH 07/73] Refactor: Extract Custom Type Casts related tests

---
 tests/CMakeLists.txt                  |   1 +
 tests/test_custom_type_casters.cpp    | 125 ++++++++++++++++++++++++++
 tests/test_custom_type_casters.py     |  89 ++++++++++++++++++
 tests/test_methods_and_attributes.cpp | 109 ----------------------
 tests/test_methods_and_attributes.py  |  87 ------------------
 5 files changed, 215 insertions(+), 196 deletions(-)
 create mode 100644 tests/test_custom_type_casters.cpp
 create mode 100644 tests/test_custom_type_casters.py

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 58993d1598..e4aba75674 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -36,6 +36,7 @@ set(PYBIND11_TEST_FILES
   test_class.cpp
   test_constants_and_functions.cpp
   test_copy_move.cpp
+  test_custom_type_casters.cpp
   test_docstring_options.cpp
   test_eigen.cpp
   test_enum.cpp
diff --git a/tests/test_custom_type_casters.cpp b/tests/test_custom_type_casters.cpp
new file mode 100644
index 0000000000..9485d3cdb2
--- /dev/null
+++ b/tests/test_custom_type_casters.cpp
@@ -0,0 +1,125 @@
+/*
+    tests/test_custom_type_casters.cpp -- tests type_caster<T>
+
+    Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include "pybind11_tests.h"
+#include "constructor_stats.h"
+
+
+// py::arg/py::arg_v testing: these arguments just record their argument when invoked
+class ArgInspector1 { public: std::string arg = "(default arg inspector 1)"; };
+class ArgInspector2 { public: std::string arg = "(default arg inspector 2)"; };
+class ArgAlwaysConverts { };
+namespace pybind11 { namespace detail {
+template <> struct type_caster<ArgInspector1> {
+public:
+    PYBIND11_TYPE_CASTER(ArgInspector1, _("ArgInspector1"));
+
+    bool load(handle src, bool convert) {
+        value.arg = "loading ArgInspector1 argument " +
+            std::string(convert ? "WITH" : "WITHOUT") + " conversion allowed.  "
+            "Argument value = " + (std::string) str(src);
+        return true;
+    }
+
+    static handle cast(const ArgInspector1 &src, return_value_policy, handle) {
+        return str(src.arg).release();
+    }
+};
+template <> struct type_caster<ArgInspector2> {
+public:
+    PYBIND11_TYPE_CASTER(ArgInspector2, _("ArgInspector2"));
+
+    bool load(handle src, bool convert) {
+        value.arg = "loading ArgInspector2 argument " +
+            std::string(convert ? "WITH" : "WITHOUT") + " conversion allowed.  "
+            "Argument value = " + (std::string) str(src);
+        return true;
+    }
+
+    static handle cast(const ArgInspector2 &src, return_value_policy, handle) {
+        return str(src.arg).release();
+    }
+};
+template <> struct type_caster<ArgAlwaysConverts> {
+public:
+    PYBIND11_TYPE_CASTER(ArgAlwaysConverts, _("ArgAlwaysConverts"));
+
+    bool load(handle, bool convert) {
+        return convert;
+    }
+
+    static handle cast(const ArgAlwaysConverts &, return_value_policy, handle) {
+        return py::none().release();
+    }
+};
+}}
+
+// test_custom_caster_destruction
+class DestructionTester {
+public:
+    DestructionTester() { print_default_created(this); }
+    ~DestructionTester() { print_destroyed(this); }
+    DestructionTester(const DestructionTester &) { print_copy_created(this); }
+    DestructionTester(DestructionTester &&) { print_move_created(this); }
+    DestructionTester &operator=(const DestructionTester &) { print_copy_assigned(this); return *this; }
+    DestructionTester &operator=(DestructionTester &&) { print_move_assigned(this); return *this; }
+};
+namespace pybind11 { namespace detail {
+template <> struct type_caster<DestructionTester> {
+    PYBIND11_TYPE_CASTER(DestructionTester, _("DestructionTester"));
+    bool load(handle, bool) { return true; }
+
+    static handle cast(const DestructionTester &, return_value_policy, handle) {
+        return py::bool_(true).release();
+    }
+};
+}}
+
+TEST_SUBMODULE(custom_type_casters, m) {
+    // test_custom_type_casters
+
+    // test_noconvert_args
+    //
+    // Test converting.  The ArgAlwaysConverts is just there to make the first no-conversion pass
+    // fail so that our call always ends up happening via the second dispatch (the one that allows
+    // some conversion).
+    class ArgInspector {
+    public:
+        ArgInspector1 f(ArgInspector1 a, ArgAlwaysConverts) { return a; }
+        std::string g(ArgInspector1 a, const ArgInspector1 &b, int c, ArgInspector2 *d, ArgAlwaysConverts) {
+            return a.arg + "\n" + b.arg + "\n" + std::to_string(c) + "\n" + d->arg;
+        }
+        static ArgInspector2 h(ArgInspector2 a, ArgAlwaysConverts) { return a; }
+    };
+    py::class_<ArgInspector>(m, "ArgInspector")
+        .def(py::init<>())
+        .def("f", &ArgInspector::f, py::arg(), py::arg() = ArgAlwaysConverts())
+        .def("g", &ArgInspector::g, "a"_a.noconvert(), "b"_a, "c"_a.noconvert()=13, "d"_a=ArgInspector2(), py::arg() = ArgAlwaysConverts())
+        .def_static("h", &ArgInspector::h, py::arg().noconvert(), py::arg() = ArgAlwaysConverts())
+        ;
+    m.def("arg_inspect_func", [](ArgInspector2 a, ArgInspector1 b, ArgAlwaysConverts) { return a.arg + "\n" + b.arg; },
+            py::arg().noconvert(false), py::arg_v(nullptr, ArgInspector1()).noconvert(true), py::arg() = ArgAlwaysConverts());
+
+    m.def("floats_preferred", [](double f) { return 0.5 * f; }, py::arg("f"));
+    m.def("floats_only", [](double f) { return 0.5 * f; }, py::arg("f").noconvert());
+    m.def("ints_preferred", [](int i) { return i / 2; }, py::arg("i"));
+    m.def("ints_only", [](int i) { return i / 2; }, py::arg("i").noconvert());
+
+    // test_custom_caster_destruction
+    // Test that `take_ownership` works on types with a custom type caster when given a pointer
+
+    // default policy: don't take ownership:
+    m.def("custom_caster_no_destroy", []() { static auto *dt = new DestructionTester(); return dt; });
+
+    m.def("custom_caster_destroy", []() { return new DestructionTester(); },
+            py::return_value_policy::take_ownership); // Takes ownership: destroy when finished
+    m.def("custom_caster_destroy_const", []() -> const DestructionTester * { return new DestructionTester(); },
+            py::return_value_policy::take_ownership); // Likewise (const doesn't inhibit destruction)
+    m.def("destruction_tester_cstats", &ConstructorStats::get<DestructionTester>, py::return_value_policy::reference);
+}
diff --git a/tests/test_custom_type_casters.py b/tests/test_custom_type_casters.py
new file mode 100644
index 0000000000..d3daa2c394
--- /dev/null
+++ b/tests/test_custom_type_casters.py
@@ -0,0 +1,89 @@
+import pytest
+from pybind11_tests import custom_type_casters as m
+
+
+def test_noconvert_args(msg):
+    a = m.ArgInspector()
+    assert msg(a.f("hi")) == """
+        loading ArgInspector1 argument WITH conversion allowed.  Argument value = hi
+    """
+    assert msg(a.g("this is a", "this is b")) == """
+        loading ArgInspector1 argument WITHOUT conversion allowed.  Argument value = this is a
+        loading ArgInspector1 argument WITH conversion allowed.  Argument value = this is b
+        13
+        loading ArgInspector2 argument WITH conversion allowed.  Argument value = (default arg inspector 2)
+    """  # noqa: E501 line too long
+    assert msg(a.g("this is a", "this is b", 42)) == """
+        loading ArgInspector1 argument WITHOUT conversion allowed.  Argument value = this is a
+        loading ArgInspector1 argument WITH conversion allowed.  Argument value = this is b
+        42
+        loading ArgInspector2 argument WITH conversion allowed.  Argument value = (default arg inspector 2)
+    """  # noqa: E501 line too long
+    assert msg(a.g("this is a", "this is b", 42, "this is d")) == """
+        loading ArgInspector1 argument WITHOUT conversion allowed.  Argument value = this is a
+        loading ArgInspector1 argument WITH conversion allowed.  Argument value = this is b
+        42
+        loading ArgInspector2 argument WITH conversion allowed.  Argument value = this is d
+    """
+    assert (a.h("arg 1") ==
+            "loading ArgInspector2 argument WITHOUT conversion allowed.  Argument value = arg 1")
+    assert msg(m.arg_inspect_func("A1", "A2")) == """
+        loading ArgInspector2 argument WITH conversion allowed.  Argument value = A1
+        loading ArgInspector1 argument WITHOUT conversion allowed.  Argument value = A2
+    """
+
+    assert m.floats_preferred(4) == 2.0
+    assert m.floats_only(4.0) == 2.0
+    with pytest.raises(TypeError) as excinfo:
+        m.floats_only(4)
+    assert msg(excinfo.value) == """
+        floats_only(): incompatible function arguments. The following argument types are supported:
+            1. (f: float) -> float
+
+        Invoked with: 4
+    """
+
+    assert m.ints_preferred(4) == 2
+    assert m.ints_preferred(True) == 0
+    with pytest.raises(TypeError) as excinfo:
+        m.ints_preferred(4.0)
+    assert msg(excinfo.value) == """
+        ints_preferred(): incompatible function arguments. The following argument types are supported:
+            1. (i: int) -> int
+
+        Invoked with: 4.0
+    """  # noqa: E501 line too long
+
+    assert m.ints_only(4) == 2
+    with pytest.raises(TypeError) as excinfo:
+        m.ints_only(4.0)
+    assert msg(excinfo.value) == """
+        ints_only(): incompatible function arguments. The following argument types are supported:
+            1. (i: int) -> int
+
+        Invoked with: 4.0
+    """
+
+
+def test_custom_caster_destruction():
+    """Tests that returning a pointer to a type that gets converted with a custom type caster gets
+    destroyed when the function has py::return_value_policy::take_ownership policy applied."""
+
+    cstats = m.destruction_tester_cstats()
+    # This one *doesn't* have take_ownership: the pointer should be used but not destroyed:
+    z = m.custom_caster_no_destroy()
+    assert cstats.alive() == 1 and cstats.default_constructions == 1
+    assert z
+
+    # take_ownership applied: this constructs a new object, casts it, then destroys it:
+    z = m.custom_caster_destroy()
+    assert z
+    assert cstats.default_constructions == 2
+
+    # Same, but with a const pointer return (which should *not* inhibit destruction):
+    z = m.custom_caster_destroy_const()
+    assert z
+    assert cstats.default_constructions == 3
+
+    # Make sure we still only have the original object (from ..._no_destroy()) alive:
+    assert cstats.alive() == 1
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 1337620941..fd95a01307 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -105,76 +105,6 @@ struct TestPropRVP {
 UserType TestPropRVP::sv1(1);
 UserType TestPropRVP::sv2(1);
 
-// py::arg/py::arg_v testing: these arguments just record their argument when invoked
-class ArgInspector1 { public: std::string arg = "(default arg inspector 1)"; };
-class ArgInspector2 { public: std::string arg = "(default arg inspector 2)"; };
-class ArgAlwaysConverts { };
-namespace pybind11 { namespace detail {
-template <> struct type_caster<ArgInspector1> {
-public:
-    PYBIND11_TYPE_CASTER(ArgInspector1, _("ArgInspector1"));
-
-    bool load(handle src, bool convert) {
-        value.arg = "loading ArgInspector1 argument " +
-            std::string(convert ? "WITH" : "WITHOUT") + " conversion allowed.  "
-            "Argument value = " + (std::string) str(src);
-        return true;
-    }
-
-    static handle cast(const ArgInspector1 &src, return_value_policy, handle) {
-        return str(src.arg).release();
-    }
-};
-template <> struct type_caster<ArgInspector2> {
-public:
-    PYBIND11_TYPE_CASTER(ArgInspector2, _("ArgInspector2"));
-
-    bool load(handle src, bool convert) {
-        value.arg = "loading ArgInspector2 argument " +
-            std::string(convert ? "WITH" : "WITHOUT") + " conversion allowed.  "
-            "Argument value = " + (std::string) str(src);
-        return true;
-    }
-
-    static handle cast(const ArgInspector2 &src, return_value_policy, handle) {
-        return str(src.arg).release();
-    }
-};
-template <> struct type_caster<ArgAlwaysConverts> {
-public:
-    PYBIND11_TYPE_CASTER(ArgAlwaysConverts, _("ArgAlwaysConverts"));
-
-    bool load(handle, bool convert) {
-        return convert;
-    }
-
-    static handle cast(const ArgAlwaysConverts &, return_value_policy, handle) {
-        return py::none().release();
-    }
-};
-}}
-
-// test_custom_caster_destruction
-class DestructionTester {
-public:
-    DestructionTester() { print_default_created(this); }
-    ~DestructionTester() { print_destroyed(this); }
-    DestructionTester(const DestructionTester &) { print_copy_created(this); }
-    DestructionTester(DestructionTester &&) { print_move_created(this); }
-    DestructionTester &operator=(const DestructionTester &) { print_copy_assigned(this); return *this; }
-    DestructionTester &operator=(DestructionTester &&) { print_move_assigned(this); return *this; }
-};
-namespace pybind11 { namespace detail {
-template <> struct type_caster<DestructionTester> {
-    PYBIND11_TYPE_CASTER(DestructionTester, _("DestructionTester"));
-    bool load(handle, bool) { return true; }
-
-    static handle cast(const DestructionTester &, return_value_policy, handle) {
-        return py::bool_(true).release();
-    }
-};
-}}
-
 // Test None-allowed py::arg argument policy
 class NoneTester { public: int answer = 42; };
 int none1(const NoneTester &obj) { return obj.answer; }
@@ -364,33 +294,6 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         .def(py::init());
 #endif
 
-    // test_noconvert_args
-    //
-    // Test converting.  The ArgAlwaysConverts is just there to make the first no-conversion pass
-    // fail so that our call always ends up happening via the second dispatch (the one that allows
-    // some conversion).
-    class ArgInspector {
-    public:
-        ArgInspector1 f(ArgInspector1 a, ArgAlwaysConverts) { return a; }
-        std::string g(ArgInspector1 a, const ArgInspector1 &b, int c, ArgInspector2 *d, ArgAlwaysConverts) {
-            return a.arg + "\n" + b.arg + "\n" + std::to_string(c) + "\n" + d->arg;
-        }
-        static ArgInspector2 h(ArgInspector2 a, ArgAlwaysConverts) { return a; }
-    };
-    py::class_<ArgInspector>(m, "ArgInspector")
-        .def(py::init<>())
-        .def("f", &ArgInspector::f, py::arg(), py::arg() = ArgAlwaysConverts())
-        .def("g", &ArgInspector::g, "a"_a.noconvert(), "b"_a, "c"_a.noconvert()=13, "d"_a=ArgInspector2(), py::arg() = ArgAlwaysConverts())
-        .def_static("h", &ArgInspector::h, py::arg().noconvert(), py::arg() = ArgAlwaysConverts())
-        ;
-    m.def("arg_inspect_func", [](ArgInspector2 a, ArgInspector1 b, ArgAlwaysConverts) { return a.arg + "\n" + b.arg; },
-            py::arg().noconvert(false), py::arg_v(nullptr, ArgInspector1()).noconvert(true), py::arg() = ArgAlwaysConverts());
-
-    m.def("floats_preferred", [](double f) { return 0.5 * f; }, py::arg("f"));
-    m.def("floats_only", [](double f) { return 0.5 * f; }, py::arg("f").noconvert());
-    m.def("ints_preferred", [](int i) { return i / 2; }, py::arg("i"));
-    m.def("ints_only", [](int i) { return i / 2; }, py::arg("i").noconvert());
-
     // test_bad_arg_default
     // Issue/PR #648: bad arg default debugging output
 #if !defined(NDEBUG)
@@ -454,18 +357,6 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     using Adapted = decltype(py::method_adaptor<RegisteredDerived>(&RegisteredDerived::do_nothing));
     static_assert(std::is_same<Adapted, void (RegisteredDerived::*)() const>::value, "");
 
-    // test_custom_caster_destruction
-    // Test that `take_ownership` works on types with a custom type caster when given a pointer
-
-    // default policy: don't take ownership:
-    m.def("custom_caster_no_destroy", []() { static auto *dt = new DestructionTester(); return dt; });
-
-    m.def("custom_caster_destroy", []() { return new DestructionTester(); },
-            py::return_value_policy::take_ownership); // Takes ownership: destroy when finished
-    m.def("custom_caster_destroy_const", []() -> const DestructionTester * { return new DestructionTester(); },
-            py::return_value_policy::take_ownership); // Likewise (const doesn't inhibit destruction)
-    m.def("destruction_tester_cstats", &ConstructorStats::get<DestructionTester>, py::return_value_policy::reference);
-
     // test_methods_and_attributes
     py::class_<RefQualified>(m, "RefQualified")
         .def(py::init<>())
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 5a10fbfa45..d1248dcf1e 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -321,69 +321,6 @@ def test_cyclic_gc():
     assert cstats.alive() == 0
 
 
-def test_noconvert_args(msg):
-    a = m.ArgInspector()
-    assert msg(a.f("hi")) == """
-        loading ArgInspector1 argument WITH conversion allowed.  Argument value = hi
-    """
-    assert msg(a.g("this is a", "this is b")) == """
-        loading ArgInspector1 argument WITHOUT conversion allowed.  Argument value = this is a
-        loading ArgInspector1 argument WITH conversion allowed.  Argument value = this is b
-        13
-        loading ArgInspector2 argument WITH conversion allowed.  Argument value = (default arg inspector 2)
-    """  # noqa: E501 line too long
-    assert msg(a.g("this is a", "this is b", 42)) == """
-        loading ArgInspector1 argument WITHOUT conversion allowed.  Argument value = this is a
-        loading ArgInspector1 argument WITH conversion allowed.  Argument value = this is b
-        42
-        loading ArgInspector2 argument WITH conversion allowed.  Argument value = (default arg inspector 2)
-    """  # noqa: E501 line too long
-    assert msg(a.g("this is a", "this is b", 42, "this is d")) == """
-        loading ArgInspector1 argument WITHOUT conversion allowed.  Argument value = this is a
-        loading ArgInspector1 argument WITH conversion allowed.  Argument value = this is b
-        42
-        loading ArgInspector2 argument WITH conversion allowed.  Argument value = this is d
-    """
-    assert (a.h("arg 1") ==
-            "loading ArgInspector2 argument WITHOUT conversion allowed.  Argument value = arg 1")
-    assert msg(m.arg_inspect_func("A1", "A2")) == """
-        loading ArgInspector2 argument WITH conversion allowed.  Argument value = A1
-        loading ArgInspector1 argument WITHOUT conversion allowed.  Argument value = A2
-    """
-
-    assert m.floats_preferred(4) == 2.0
-    assert m.floats_only(4.0) == 2.0
-    with pytest.raises(TypeError) as excinfo:
-        m.floats_only(4)
-    assert msg(excinfo.value) == """
-        floats_only(): incompatible function arguments. The following argument types are supported:
-            1. (f: float) -> float
-
-        Invoked with: 4
-    """
-
-    assert m.ints_preferred(4) == 2
-    assert m.ints_preferred(True) == 0
-    with pytest.raises(TypeError) as excinfo:
-        m.ints_preferred(4.0)
-    assert msg(excinfo.value) == """
-        ints_preferred(): incompatible function arguments. The following argument types are supported:
-            1. (i: int) -> int
-
-        Invoked with: 4.0
-    """  # noqa: E501 line too long
-
-    assert m.ints_only(4) == 2
-    with pytest.raises(TypeError) as excinfo:
-        m.ints_only(4.0)
-    assert msg(excinfo.value) == """
-        ints_only(): incompatible function arguments. The following argument types are supported:
-            1. (i: int) -> int
-
-        Invoked with: 4.0
-    """
-
-
 def test_bad_arg_default(msg):
     from pybind11_tests import debug_enabled
 
@@ -488,30 +425,6 @@ def test_unregistered_base_implementations():
     assert a.ro_value_prop == 1.75
 
 
-def test_custom_caster_destruction():
-    """Tests that returning a pointer to a type that gets converted with a custom type caster gets
-    destroyed when the function has py::return_value_policy::take_ownership policy applied."""
-
-    cstats = m.destruction_tester_cstats()
-    # This one *doesn't* have take_ownership: the pointer should be used but not destroyed:
-    z = m.custom_caster_no_destroy()
-    assert cstats.alive() == 1 and cstats.default_constructions == 1
-    assert z
-
-    # take_ownership applied: this constructs a new object, casts it, then destroys it:
-    z = m.custom_caster_destroy()
-    assert z
-    assert cstats.default_constructions == 2
-
-    # Same, but with a const pointer return (which should *not* inhibit destruction):
-    z = m.custom_caster_destroy_const()
-    assert z
-    assert cstats.default_constructions == 3
-
-    # Make sure we still only have the original object (from ..._no_destroy()) alive:
-    assert cstats.alive() == 1
-
-
 def test_ref_qualified():
     """Tests that explicit lvalue ref-qualified methods can be called just like their
     non ref-qualified counterparts."""

From d031efe78890f673e6ea8d8f2175058881b1e006 Mon Sep 17 00:00:00 2001
From: Lin Hsu <linhsu0723@qq.com>
Date: Sat, 13 Jun 2020 23:24:44 +0800
Subject: [PATCH 08/73] Typo

---
 docs/faq.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/faq.rst b/docs/faq.rst
index 4d491fb87f..b68562910a 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -5,7 +5,7 @@ Frequently asked questions
 ===========================================================
 
 1. Make sure that the name specified in PYBIND11_MODULE is identical to the
-filename of the extension library (without prefixes such as .so)
+filename of the extension library (without suffixes such as .so)
 
 2. If the above did not fix the issue, you are likely using an incompatible
 version of Python (for instance, the extension library was compiled against

From 8908552dfce61cc4d0d428c402b416c28283cb9c Mon Sep 17 00:00:00 2001
From: Guilherme Dantas <guidanoli@hotmail.com>
Date: Mon, 27 Apr 2020 17:19:17 -0300
Subject: [PATCH 09/73] typo

---
 docs/advanced/pycpp/numpy.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index 458f99e978..3d9c90cb42 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -67,7 +67,7 @@ specification.
 To create a C++ function that can take a Python buffer object as an argument,
 simply use the type ``py::buffer`` as one of its arguments. Buffers can exist
 in a great variety of configurations, hence some safety checks are usually
-necessary in the function body. Below, you can see an basic example on how to
+necessary in the function body. Below, you can see a basic example on how to
 define a custom constructor for the Eigen double precision matrix
 (``Eigen::MatrixXd``) type, which supports initialization from compatible
 buffer objects (e.g. a NumPy matrix).

From 3618807dca91f58f3e1b2709f5bb6e0cab441cd2 Mon Sep 17 00:00:00 2001
From: Takahiro Ishikawa <ishikawatt@gmail.com>
Date: Mon, 4 May 2020 19:40:42 +0900
Subject: [PATCH 10/73] Fix python.lib name

pybind11_add_module fails because FindPythonLibsNew.cmake try to link PythonXX.lib, but the first letter "p" should be lowercase.
---
 tools/FindPythonLibsNew.cmake | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index 9ea6036e33..31d1ddb730 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -146,14 +146,14 @@ string(REGEX REPLACE "\\\\" "/" PYTHON_SITE_PACKAGES "${PYTHON_SITE_PACKAGES}")
 
 if(CMAKE_HOST_WIN32 AND NOT (MINGW AND DEFINED ENV{MSYSTEM}))
     set(PYTHON_LIBRARY
-        "${PYTHON_PREFIX}/libs/Python${PYTHON_LIBRARY_SUFFIX}.lib")
+        "${PYTHON_PREFIX}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
 
     # when run in a venv, PYTHON_PREFIX points to it. But the libraries remain in the
     # original python installation. They may be found relative to PYTHON_INCLUDE_DIR.
     if(NOT EXISTS "${PYTHON_LIBRARY}")
         get_filename_component(_PYTHON_ROOT ${PYTHON_INCLUDE_DIR} DIRECTORY)
         set(PYTHON_LIBRARY
-            "${_PYTHON_ROOT}/libs/Python${PYTHON_LIBRARY_SUFFIX}.lib")
+            "${_PYTHON_ROOT}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
     endif()
 
     # raise an error if the python libs are still not found.

From 141e8cc0afad1e06904fab36ff4ca5f8b64f44e7 Mon Sep 17 00:00:00 2001
From: Nils Leif Fischer <nils.fischer@aei.mpg.de>
Date: Fri, 26 Jun 2020 12:15:10 +0200
Subject: [PATCH 11/73] Fix uninitialized-variables cmake warnings

---
 tools/FindPythonLibsNew.cmake | 12 +++++++++++-
 tools/pybind11Tools.cmake     | 31 ++++++++++++++++++++++++-------
 2 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index 31d1ddb730..d0c8fa2603 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -56,6 +56,9 @@ if(PYTHONLIBS_FOUND AND PYTHON_MODULE_EXTENSION)
 endif()
 
 # Use the Python interpreter to find the libs.
+if(NOT PythonLibsNew_FIND_VERSION)
+    set(PythonLibsNew_FIND_VERSION "")
+endif()
 if(PythonLibsNew_FIND_REQUIRED)
     find_package(PythonInterp ${PythonLibsNew_FIND_VERSION} REQUIRED)
 else()
@@ -192,11 +195,18 @@ MARK_AS_ADVANCED(
 # module.
 SET(PYTHON_INCLUDE_DIRS "${PYTHON_INCLUDE_DIR}")
 SET(PYTHON_LIBRARIES "${PYTHON_LIBRARY}")
+if(NOT PYTHON_DEBUG_LIBRARY)
+    SET(PYTHON_DEBUG_LIBRARY "")
+endif()
 SET(PYTHON_DEBUG_LIBRARIES "${PYTHON_DEBUG_LIBRARY}")
 
 find_package_message(PYTHON
     "Found PythonLibs: ${PYTHON_LIBRARY}"
-    "${PYTHON_EXECUTABLE}${PYTHON_VERSION}")
+    "${PYTHON_EXECUTABLE}${PYTHON_VERSION_STRING}")
 
 set(PYTHONLIBS_FOUND TRUE)
 set(PythonLibsNew_FOUND TRUE)
+
+if(NOT PYTHON_MODULE_PREFIX)
+    SET(PYTHON_MODULE_PREFIX "")
+endif()
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 8d85dd4ebb..a3603abe97 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -33,7 +33,7 @@ if(NOT CMAKE_VERSION VERSION_LESS 3.1)
   endif()
 endif()
 
-# Fall back to heuristics 
+# Fall back to heuristics
 if(NOT PYBIND11_CPP_STANDARD AND NOT CMAKE_CXX_STANDARD)
   if(MSVC)
     set(PYBIND11_CPP_STANDARD /std:c++14)
@@ -142,17 +142,32 @@ function(pybind11_add_module target_name)
 
   if(ARG_EXCLUDE_FROM_ALL)
     set(exclude_from_all EXCLUDE_FROM_ALL)
+  else()
+    set(exclude_from_all "")
   endif()
 
   add_library(${target_name} ${lib_type} ${exclude_from_all} ${ARG_UNPARSED_ARGUMENTS})
 
   if(ARG_SYSTEM)
     set(inc_isystem SYSTEM)
+  else()
+    set(inc_isystem "")
+  endif()
+
+  set(PYBIND11_INCLUDE_DIR_SELECTED "")
+  if(PYBIND11_INCLUDE_DIR)
+    # from project CMakeLists.txt
+    set(PYBIND11_INCLUDE_DIR_SELECTED ${PYBIND11_INCLUDE_DIR})
+  elseif(pybind11_INCLUDE_DIR)
+    # from pybind11Config
+    set(PYBIND11_INCLUDE_DIR_SELECTED ${pybind11_INCLUDE_DIR})
+  else()
+    message(FATAL "No pybind11_INCLUDE_DIR available. Use "
+      "find_package(pybind11) before calling pybind11_add_module.")
   endif()
 
   target_include_directories(${target_name} ${inc_isystem}
-    PRIVATE ${PYBIND11_INCLUDE_DIR}  # from project CMakeLists.txt
-    PRIVATE ${pybind11_INCLUDE_DIR}  # from pybind11Config
+    PRIVATE ${PYBIND11_INCLUDE_DIR_SELECTED}
     PRIVATE ${PYTHON_INCLUDE_DIRS})
 
   # Python debug libraries expose slightly different objects
@@ -201,10 +216,12 @@ function(pybind11_add_module target_name)
   endif()
 
   # Make sure C++11/14 are enabled
-  if(CMAKE_VERSION VERSION_LESS 3.3)
-    target_compile_options(${target_name} PUBLIC ${PYBIND11_CPP_STANDARD})
-  else()
-    target_compile_options(${target_name} PUBLIC $<$<COMPILE_LANGUAGE:CXX>:${PYBIND11_CPP_STANDARD}>)
+  if(PYBIND11_CPP_STANDARD)
+    if(CMAKE_VERSION VERSION_LESS 3.3)
+      target_compile_options(${target_name} PUBLIC ${PYBIND11_CPP_STANDARD})
+    else()
+      target_compile_options(${target_name} PUBLIC $<$<COMPILE_LANGUAGE:CXX>:${PYBIND11_CPP_STANDARD}>)
+    endif()
   endif()
 
   if(ARG_NO_EXTRAS)

From fc3a4490b879cce20a7e1b1454f0f7f5a0bc08c6 Mon Sep 17 00:00:00 2001
From: Wenzel Jakob <wenzel.jakob@epfl.ch>
Date: Wed, 1 Jul 2020 00:25:17 +0200
Subject: [PATCH 12/73] Minor clarification (@AntoinePrv, #2083)

---
 docs/advanced/classes.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 70393b55ed..0d50cba51b 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -298,8 +298,8 @@ The classes are then registered with pybind11 using:
 .. code-block:: cpp
 
     py::class_<Animal, PyAnimal<>> animal(m, "Animal");
-    py::class_<Dog, PyDog<>> dog(m, "Dog");
-    py::class_<Husky, PyDog<Husky>> husky(m, "Husky");
+    py::class_<Dog, Animal, PyDog<>> dog(m, "Dog");
+    py::class_<Husky, Dog, PyDog<Husky>> husky(m, "Husky");
     // ... add animal, dog, husky definitions
 
 Note that ``Husky`` did not require a dedicated trampoline template class at

From d54d6d8c613914a7063897d5ddddc62348ffe74a Mon Sep 17 00:00:00 2001
From: Yannick Jadoul <yannick.jadoul@belgacom.net>
Date: Wed, 1 Jul 2020 01:53:09 +0200
Subject: [PATCH 13/73] Adding pybind11::cast overload for rvalue references
 (#1260)

* Adding pybind11::cast overload for rvalue references
---
 include/pybind11/cast.h  | 11 +++++++----
 tests/test_smart_ptr.cpp |  3 ++-
 tests/test_smart_ptr.py  |  3 +++
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 28283da8f3..9fa5e21d0c 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1725,13 +1725,16 @@ T cast(const handle &handle) { return T(reinterpret_borrow<object>(handle)); }
 
 // C++ type -> py::object
 template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> = 0>
-object cast(const T &value, return_value_policy policy = return_value_policy::automatic_reference,
+object cast(T &&value, return_value_policy policy = return_value_policy::automatic_reference,
             handle parent = handle()) {
+    using no_ref_T = typename std::remove_reference<T>::type;
     if (policy == return_value_policy::automatic)
-        policy = std::is_pointer<T>::value ? return_value_policy::take_ownership : return_value_policy::copy;
+        policy = std::is_pointer<no_ref_T>::value ? return_value_policy::take_ownership :
+                 std::is_lvalue_reference<T>::value ? return_value_policy::copy : return_value_policy::move;
     else if (policy == return_value_policy::automatic_reference)
-        policy = std::is_pointer<T>::value ? return_value_policy::reference : return_value_policy::copy;
-    return reinterpret_steal<object>(detail::make_caster<T>::cast(value, policy, parent));
+        policy = std::is_pointer<no_ref_T>::value ? return_value_policy::reference :
+                 std::is_lvalue_reference<T>::value ? return_value_policy::copy : return_value_policy::move;
+    return reinterpret_steal<object>(detail::make_caster<T>::cast(std::forward<T>(value), policy, parent));
 }
 
 template <typename T> T handle::cast() const { return pybind11::cast<T>(*this); }
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 87c9be8c2b..6f8f3821a5 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -291,7 +291,8 @@ TEST_SUBMODULE(smart_ptr, m) {
         ~C() { print_destroyed(this); }
     };
     py::class_<C, custom_unique_ptr<C>>(m, "TypeWithMoveOnlyHolder")
-        .def_static("make", []() { return custom_unique_ptr<C>(new C); });
+        .def_static("make", []() { return custom_unique_ptr<C>(new C); })
+        .def_static("make_as_object", []() { return py::cast(custom_unique_ptr<C>(new C)); });
 
     // test_holder_with_addressof_operator
     struct TypeForHolderWithAddressOf {
diff --git a/tests/test_smart_ptr.py b/tests/test_smart_ptr.py
index c6627043bd..d275b3dc9b 100644
--- a/tests/test_smart_ptr.py
+++ b/tests/test_smart_ptr.py
@@ -218,7 +218,10 @@ def test_shared_ptr_from_this_and_references():
 
 def test_move_only_holder():
     a = m.TypeWithMoveOnlyHolder.make()
+    b = m.TypeWithMoveOnlyHolder.make_as_object()
     stats = ConstructorStats.get(m.TypeWithMoveOnlyHolder)
+    assert stats.alive() == 2
+    del b
     assert stats.alive() == 1
     del a
     assert stats.alive() == 0

From 1b0bf352fa51f07402f998d358565bf141f94c69 Mon Sep 17 00:00:00 2001
From: Dustin Spicuzza <dustin@virtualroadside.com>
Date: Tue, 7 Jul 2020 06:04:06 -0400
Subject: [PATCH 14/73] Throw TypeError when subclasses forget to call __init__
 (#2152)

- Fixes #2103
---
 docs/advanced/classes.rst       |  5 +++++
 include/pybind11/detail/class.h | 27 +++++++++++++++++++++++++++
 tests/test_class.py             | 21 +++++++++++++++++++++
 3 files changed, 53 insertions(+)

diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index 0d50cba51b..b3da0378c0 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -149,6 +149,11 @@ memory for the C++ portion of the instance will be left uninitialized, which
 will generally leave the C++ instance in an invalid state and cause undefined
 behavior if the C++ instance is subsequently used.
 
+.. versionadded:: 2.5.1
+
+   The default pybind11 metaclass will throw a ``TypeError`` when it detects
+   that ``__init__`` was not called by a derived class.
+
 Here is an example:
 
 .. code-block:: python
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index a05edeb4c5..e5783d9f65 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -156,6 +156,31 @@ extern "C" inline PyObject *pybind11_meta_getattro(PyObject *obj, PyObject *name
 }
 #endif
 
+/// metaclass `__call__` function that is used to create all pybind11 objects.
+extern "C" inline PyObject *pybind11_meta_call(PyObject *type, PyObject *args, PyObject *kwargs) {
+
+    // use the default metaclass call to create/initialize the object
+    PyObject *self = PyType_Type.tp_call(type, args, kwargs);
+    if (self == nullptr) {
+        return nullptr;
+    }
+
+    // This must be a pybind11 instance
+    auto instance = reinterpret_cast<detail::instance *>(self);
+
+    // Ensure that the base __init__ function(s) were called
+    for (auto vh : values_and_holders(instance)) {
+        if (!vh.holder_constructed()) {
+            PyErr_Format(PyExc_TypeError, "%.200s.__init__() must be called when overriding __init__",
+                         vh.type->type->tp_name);
+            Py_DECREF(self);
+            return nullptr;
+        }
+    }
+
+    return self;
+}
+
 /** This metaclass is assigned by default to all pybind11 types and is required in order
     for static properties to function correctly. Users may override this using `py::metaclass`.
     Return value: New reference. */
@@ -181,6 +206,8 @@ inline PyTypeObject* make_default_metaclass() {
     type->tp_base = type_incref(&PyType_Type);
     type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HEAPTYPE;
 
+    type->tp_call = pybind11_meta_call;
+
     type->tp_setattro = pybind11_meta_setattro;
 #if PY_MAJOR_VERSION >= 3
     type->tp_getattro = pybind11_meta_getattro;
diff --git a/tests/test_class.py b/tests/test_class.py
index e58fef6980..9807535e8e 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -101,6 +101,27 @@ def test_inheritance(msg):
     assert "No constructor defined!" in str(excinfo.value)
 
 
+def test_inheritance_init(msg):
+
+    # Single base
+    class Python(m.Pet):
+        def __init__(self):
+            pass
+    with pytest.raises(TypeError) as exc_info:
+        Python()
+    assert msg(exc_info.value) == "m.class_.Pet.__init__() must be called when overriding __init__"
+
+    # Multiple bases
+    class RabbitHamster(m.Rabbit, m.Hamster):
+        def __init__(self):
+            m.Rabbit.__init__(self, "RabbitHamster")
+
+    with pytest.raises(TypeError) as exc_info:
+        RabbitHamster()
+    expected = "m.class_.Hamster.__init__() must be called when overriding __init__"
+    assert msg(exc_info.value) == expected
+
+
 def test_automatic_upcasting():
     assert type(m.return_class_1()).__name__ == "DerivedClass1"
     assert type(m.return_class_2()).__name__ == "DerivedClass2"

From f2226aefe0f679c61e6eaf5d6f315796fc28cebc Mon Sep 17 00:00:00 2001
From: Robert Haschke <rhaschke@users.noreply.github.com>
Date: Tue, 7 Jul 2020 15:56:07 +0200
Subject: [PATCH 15/73] Allow perfect forwarding of method args (#2048)

---
 include/pybind11/pybind11.h           | 4 ++--
 tests/test_methods_and_attributes.cpp | 5 +++++
 tests/test_methods_and_attributes.py  | 4 ++--
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 7a6e56302e..45828dba89 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -75,7 +75,7 @@ class cpp_function : public function {
     /// Construct a cpp_function from a class method (non-const, no ref-qualifier)
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     cpp_function(Return (Class::*f)(Arg...), const Extra&... extra) {
-        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(args...); },
+        initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
                    (Return (*) (Class *, Arg...)) nullptr, extra...);
     }
 
@@ -91,7 +91,7 @@ class cpp_function : public function {
     /// Construct a cpp_function from a class method (const, no ref-qualifier)
     template <typename Return, typename Class, typename... Arg, typename... Extra>
     cpp_function(Return (Class::*f)(Arg...) const, const Extra&... extra) {
-        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(args...); },
+        initialize([f](const Class *c, Arg... args) -> Return { return (c->*f)(std::forward<Arg>(args)...); },
                    (Return (*)(const Class *, Arg ...)) nullptr, extra...);
     }
 
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index fd95a01307..901f2046c4 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -21,6 +21,7 @@ class ExampleMandA {
     ExampleMandA() { print_default_created(this); }
     ExampleMandA(int value) : value(value) { print_created(this, value); }
     ExampleMandA(const ExampleMandA &e) : value(e.value) { print_copy_created(this); }
+    ExampleMandA(std::string&&) {}
     ExampleMandA(ExampleMandA &&e) : value(e.value) { print_move_created(this); }
     ~ExampleMandA() { print_destroyed(this); }
 
@@ -43,6 +44,8 @@ class ExampleMandA {
     void add9(int *other) { value += *other; }                      // passing by pointer
     void add10(const int *other) { value += *other; }               // passing by const pointer
 
+    void consume_str(std::string&&) {}
+
     ExampleMandA self1() { return *this; }                          // return by value
     ExampleMandA &self2() { return *this; }                         // return by reference
     const ExampleMandA &self3() { return *this; }                   // return by const reference
@@ -150,6 +153,7 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     py::class_<ExampleMandA> emna(m, "ExampleMandA");
     emna.def(py::init<>())
         .def(py::init<int>())
+        .def(py::init<std::string&&>())
         .def(py::init<const ExampleMandA&>())
         .def("add1", &ExampleMandA::add1)
         .def("add2", &ExampleMandA::add2)
@@ -161,6 +165,7 @@ TEST_SUBMODULE(methods_and_attributes, m) {
         .def("add8", &ExampleMandA::add8)
         .def("add9", &ExampleMandA::add9)
         .def("add10", &ExampleMandA::add10)
+        .def("consume_str", &ExampleMandA::consume_str)
         .def("self1", &ExampleMandA::self1)
         .def("self2", &ExampleMandA::self2)
         .def("self3", &ExampleMandA::self3)
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index d1248dcf1e..8bda7a8b20 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -58,8 +58,8 @@ def test_methods_and_attributes():
     assert cstats.alive() == 0
     assert cstats.values() == ["32"]
     assert cstats.default_constructions == 1
-    assert cstats.copy_constructions == 3
-    assert cstats.move_constructions >= 1
+    assert cstats.copy_constructions == 2
+    assert cstats.move_constructions >= 2
     assert cstats.copy_assignments == 0
     assert cstats.move_assignments == 0
 

From 0d70f0e18eec60786499faba53de4d72583ba2f7 Mon Sep 17 00:00:00 2001
From: Isuru Fernando <isuruf@gmail.com>
Date: Tue, 7 Jul 2020 08:58:16 -0500
Subject: [PATCH 16/73] PyPy3 support (#2146)

* Error out eval_file

* Enable dynamic attribute support for Pypy >= 6

* Add a test for dynamic attribute support

* Skip test for eval_file on pypy

* Workaround for __qualname__ on PyPy3

* Add a PyPy3.6 7.3.0 build

* Only disable in PyPy3

* Fix travis testing

* No numpy and scipy for pypy

* Enable test on pypy2

* Fix logic in eval_file

* Skip a few tests due to bugs in PyPy

* scipy wheels are broken. make pypy2 a failrue

Co-authored-by: Andreas Kloeckner <inform@tiker.net>
---
 .travis.yml                         | 11 ++++++-----
 include/pybind11/detail/class.h     |  4 ++--
 include/pybind11/eval.h             | 15 +++++++++++++++
 tests/conftest.py                   |  5 +++++
 tests/test_eval.py                  |  7 ++++++-
 tests/test_local_bindings.py        |  1 +
 tests/test_multiple_inheritance.cpp |  2 +-
 tests/test_multiple_inheritance.py  |  4 +++-
 8 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index f9a9065412..0e504582f3 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -192,9 +192,8 @@ matrix:
           make pytest -j 2"
         set +ex
   allow_failures:
-    - name: PyPy 7.3, Python 2.7, c++11, gcc 4.8
-    - name: PyPy 7.3, Python 3.6, c++11, gcc 5
     - name: Python 3.9 beta, c++17, gcc 7 (w/o numpy/scipy)
+    - name: PyPy 7.3, Python 2.7, c++11, gcc 4.8
 cache:
   directories:
   - $HOME/.local/bin
@@ -278,15 +277,17 @@ install:
     fi
 
     export NPY_NUM_BUILD_JOBS=2
-    echo "Installing pytest, numpy, scipy..."
     local PIP_CMD=""
     if [ -n "$PYPY" ]; then
       # For expediency, install only versions that are available on the extra index.
+      echo "Not installing numpy, scipy as working wheels are not available"
+      # travis_wait 30 $PY_CMD -m pip install --user --upgrade --extra-index-url https://antocuni.github.io/pypy-wheels/manylinux2010 \
+      #    numpy scipy
+      echo "Installing pytest"
       travis_wait 30 \
-        $PY_CMD -m pip install --user --upgrade --extra-index-url https://antocuni.github.io/pypy-wheels/manylinux2010 \
-          numpy scipy
         $PY_CMD -m pip install --user --upgrade pytest
     else
+      echo "Installing pytest, numpy, scipy..."
       $PY_CMD -m pip install --user --upgrade pytest numpy scipy
     fi
     echo "done."
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index e5783d9f65..f6b89c20e1 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -15,7 +15,7 @@
 NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 NAMESPACE_BEGIN(detail)
 
-#if PY_VERSION_HEX >= 0x03030000
+#if PY_VERSION_HEX >= 0x03030000 && !defined(PYPY_VERSION)
 #  define PYBIND11_BUILTIN_QUALNAME
 #  define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)
 #else
@@ -475,7 +475,7 @@ extern "C" inline int pybind11_clear(PyObject *self) {
 /// Give instances of this type a `__dict__` and opt into garbage collection.
 inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type) {
     auto type = &heap_type->ht_type;
-#if defined(PYPY_VERSION)
+#if defined(PYPY_VERSION) && (PYPY_VERSION_NUM < 0x06000000)
     pybind11_fail(std::string(type->tp_name) + ": dynamic attributes are "
                                                "currently not supported in "
                                                "conjunction with PyPy!");
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index ea85ba1dbe..422e629f5b 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -66,6 +66,20 @@ void exec(const char (&s)[N], object global = globals(), object local = object()
     eval<eval_statements>(s, global, local);
 }
 
+#if defined(PYPY_VERSION) && PY_VERSION_HEX >= 0x3000000
+template <eval_mode mode = eval_statements>
+object eval_file(str, object, object) {
+    pybind11_fail("eval_file not supported in PyPy3. Use eval");
+}
+template <eval_mode mode = eval_statements>
+object eval_file(str, object) {
+    pybind11_fail("eval_file not supported in PyPy3. Use eval");
+}
+template <eval_mode mode = eval_statements>
+object eval_file(str) {
+    pybind11_fail("eval_file not supported in PyPy3. Use eval");
+}
+#else
 template <eval_mode mode = eval_statements>
 object eval_file(str fname, object global = globals(), object local = object()) {
     if (!local)
@@ -113,5 +127,6 @@ object eval_file(str fname, object global = globals(), object local = object())
         throw error_already_set();
     return reinterpret_steal<object>(result);
 }
+#endif
 
 NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/tests/conftest.py b/tests/conftest.py
index 57f681c66f..58ebecaf9c 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -215,6 +215,11 @@ def pytest_configure():
     pytest.requires_eigen_and_scipy = skipif(
         not have_eigen or not scipy, reason="eigen and/or scipy are not installed")
     pytest.unsupported_on_pypy = skipif(pypy, reason="unsupported on PyPy")
+    pytest.bug_in_pypy = pytest.mark.xfail(pypy, reason="bug in PyPy")
+    pytest.unsupported_on_pypy3 = skipif(pypy and sys.version_info.major >= 3,
+                                         reason="unsupported on PyPy3")
+    pytest.unsupported_on_pypy_lt_6 = skipif(pypy and sys.pypy_version_info[0] < 6,
+                                             reason="unsupported on PyPy<6")
     pytest.unsupported_on_py2 = skipif(sys.version_info.major < 3,
                                        reason="unsupported on Python 2.x")
     pytest.gc_collect = gc_collect
diff --git a/tests/test_eval.py b/tests/test_eval.py
index bda4ef6bf6..94228e7d27 100644
--- a/tests/test_eval.py
+++ b/tests/test_eval.py
@@ -1,4 +1,5 @@
 import os
+import pytest
 from pybind11_tests import eval_ as m
 
 
@@ -10,8 +11,12 @@ def test_evals(capture):
     assert m.test_eval()
     assert m.test_eval_single_statement()
 
+    assert m.test_eval_failure()
+
+
+@pytest.unsupported_on_pypy3
+def test_eval_file():
     filename = os.path.join(os.path.dirname(__file__), "test_eval_call.py")
     assert m.test_eval_file(filename)
 
-    assert m.test_eval_failure()
     assert m.test_eval_file_failure()
diff --git a/tests/test_local_bindings.py b/tests/test_local_bindings.py
index b380376e2b..be841a70c3 100644
--- a/tests/test_local_bindings.py
+++ b/tests/test_local_bindings.py
@@ -152,6 +152,7 @@ def test_internal_locals_differ():
     assert m.local_cpp_types_addr() != cm.local_cpp_types_addr()
 
 
+@pytest.bug_in_pypy
 def test_stl_caster_vs_stl_bind(msg):
     """One module uses a generic vector caster from `<pybind11/stl.h>` while the other
     exports `std::vector<int>` via `py:bind_vector` and `py::module_local`"""
diff --git a/tests/test_multiple_inheritance.cpp b/tests/test_multiple_inheritance.cpp
index ba1674fb2d..70e3417854 100644
--- a/tests/test_multiple_inheritance.cpp
+++ b/tests/test_multiple_inheritance.cpp
@@ -193,7 +193,7 @@ TEST_SUBMODULE(multiple_inheritance, m) {
         .def_readwrite_static("static_value", &VanillaStaticMix2::static_value);
 
 
-#if !defined(PYPY_VERSION)
+#if !(defined(PYPY_VERSION) && (PYPY_VERSION_NUM < 0x06000000))
     struct WithDict { };
     struct VanillaDictMix1 : Vanilla, WithDict { };
     struct VanillaDictMix2 : WithDict, Vanilla { };
diff --git a/tests/test_multiple_inheritance.py b/tests/test_multiple_inheritance.py
index 475dd3b3d8..7a6e4a0852 100644
--- a/tests/test_multiple_inheritance.py
+++ b/tests/test_multiple_inheritance.py
@@ -10,6 +10,7 @@ def test_multiple_inheritance_cpp():
     assert mt.bar() == 4
 
 
+@pytest.bug_in_pypy
 def test_multiple_inheritance_mix1():
     class Base1:
         def __init__(self, i):
@@ -49,6 +50,7 @@ def __init__(self, i, j):
     assert mt.bar() == 4
 
 
+@pytest.bug_in_pypy
 def test_multiple_inheritance_python():
 
     class MI1(m.Base1, m.Base2):
@@ -253,7 +255,7 @@ def test_mi_static_properties():
         assert d.static_value == 0
 
 
-@pytest.unsupported_on_pypy
+@pytest.unsupported_on_pypy_lt_6
 def test_mi_dynamic_attributes():
     """Mixing bases with and without dynamic attribute support"""
 

From f980d76d38dda8e9ce78e68e27b4c2026681bf51 Mon Sep 17 00:00:00 2001
From: Yannick Jadoul <yannick.jadoul@belgacom.net>
Date: Thu, 9 Jul 2020 00:14:41 +0200
Subject: [PATCH 17/73] Change NAMESPACE_* macros into PYBIND11_NAMESPACE_*
 (#2283)

* Change NAMESPACE_BEGIN and NAMESPACE_END macros into PYBIND11_NAMESPACE_BEGIN and PYBIND11_NAMESPACE_END

* Fix sudden HomeBrew 'python not installed' error

* Sweep difference in 'Class.__init__() must be called when overriding __init__' error message between CPython and PyPy under the rug

* Homebrew updated to 3.8 yesterday.

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .travis.yml                         |  6 +++---
 include/pybind11/attr.h             |  8 ++++----
 include/pybind11/buffer_info.h      |  8 ++++----
 include/pybind11/cast.h             | 20 +++++++++---------
 include/pybind11/chrono.h           |  8 ++++----
 include/pybind11/complex.h          |  8 ++++----
 include/pybind11/detail/class.h     |  8 ++++----
 include/pybind11/detail/common.h    | 32 +++++++++++++----------------
 include/pybind11/detail/descr.h     |  8 ++++----
 include/pybind11/detail/init.h      | 12 +++++------
 include/pybind11/detail/internals.h |  8 ++++----
 include/pybind11/detail/typeid.h    |  8 ++++----
 include/pybind11/eigen.h            |  8 ++++----
 include/pybind11/embed.h            |  8 ++++----
 include/pybind11/eval.h             |  4 ++--
 include/pybind11/functional.h       |  8 ++++----
 include/pybind11/iostream.h         | 12 +++++------
 include/pybind11/numpy.h            | 12 +++++------
 include/pybind11/operators.h        |  8 ++++----
 include/pybind11/options.h          |  4 ++--
 include/pybind11/pybind11.h         | 24 +++++++++++-----------
 include/pybind11/pytypes.h          | 32 ++++++++++++++---------------
 include/pybind11/stl.h              |  8 ++++----
 include/pybind11/stl_bind.h         | 12 +++++------
 tests/pybind11_tests.h              |  8 ++++----
 tests/test_class.py                 | 10 ++++++---
 tests/test_copy_move.cpp            |  8 ++++----
 27 files changed, 150 insertions(+), 150 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 0e504582f3..12067bca8f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -147,9 +147,9 @@ matrix:
     osx_image: xcode7.3
     env: PYTHON=2.7 CPP=14 CLANG CMAKE=1
   - os: osx
-    name: Python 3.7, c++14, AppleClang 9, Debug build
+    name: Python 3.8, c++14, AppleClang 9, Debug build
     osx_image: xcode9.4
-    env: PYTHON=3.7 CPP=14 CLANG DEBUG=1
+    env: PYTHON=3.8 CPP=14 CLANG DEBUG=1
   # Test a PyPy 2.7 build
   - os: linux
     dist: trusty
@@ -243,7 +243,7 @@ before_install:
       PY_CMD=python$PYTHON
       if [ "$TRAVIS_OS_NAME" = "osx" ]; then
         if [ "$PY" = "3" ]; then
-          brew update && brew unlink python@2 && brew upgrade python
+          brew update && brew unlink python@2 && (brew upgrade python || brew install python)
         else
           curl -fsSL https://bootstrap.pypa.io/get-pip.py | $PY_CMD - --user
         fi
diff --git a/include/pybind11/attr.h b/include/pybind11/attr.h
index 58390239af..54065fc9e1 100644
--- a/include/pybind11/attr.h
+++ b/include/pybind11/attr.h
@@ -12,7 +12,7 @@
 
 #include "cast.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /// \addtogroup annotations
 /// @{
@@ -113,7 +113,7 @@ struct call_guard<T, Ts...> {
 
 /// @} annotations
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 /* Forward declarations */
 enum op_id : int;
 enum op_type : int;
@@ -524,5 +524,5 @@ constexpr bool expected_num_args(size_t nargs, bool has_args, bool has_kwargs) {
     return named == 0 || (self + named + has_args + has_kwargs) == nargs;
 }
 
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 1f4115a1fa..0bf42880b7 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -11,7 +11,7 @@
 
 #include "detail/common.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /// Information record describing a Python buffer object
 struct buffer_info {
@@ -94,7 +94,7 @@ struct buffer_info {
     bool ownview = false;
 };
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <typename T, typename SFINAE = void> struct compare_buffer_info {
     static bool compare(const buffer_info& b) {
@@ -110,5 +110,5 @@ template <typename T> struct compare_buffer_info<T, detail::enable_if_t<std::is_
     }
 };
 
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 9fa5e21d0c..d788992df1 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -36,8 +36,8 @@
 #  define PYBIND11_HAS_U8STRING
 #endif
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// A life support system for temporary objects created by `type_caster::load()`.
 /// Adding a patient will keep it alive up until the enclosing function returns.
@@ -816,7 +816,7 @@ template <typename Container> struct is_copy_assignable<Container, enable_if_t<a
 template <typename T1, typename T2> struct is_copy_assignable<std::pair<T1, T2>>
     : all_of<is_copy_assignable<T1>, is_copy_assignable<T2>> {};
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 // polymorphic_type_hook<itype>::get(src, tinfo) determines whether the object pointed
 // to by `src` actually is an instance of some class derived from `itype`.
@@ -855,7 +855,7 @@ struct polymorphic_type_hook_base<itype, detail::enable_if_t<std::is_polymorphic
 template <typename itype, typename SFINAE = void>
 struct polymorphic_type_hook : public polymorphic_type_hook_base<itype> {};
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Generic type caster for objects stored on the heap
 template <typename type> class type_caster_base : public type_caster_generic {
@@ -1708,7 +1708,7 @@ template <typename T> make_caster<T> load_type(const handle &handle) {
     return conv;
 }
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 // pytype -> C++ type
 template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> = 0>
@@ -1779,7 +1779,7 @@ template <typename T> T object::cast() && { return pybind11::cast<T>(std::move(*
 template <> inline void object::cast() const & { return; }
 template <> inline void object::cast() && { return; }
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Declared in pytypes.h:
 template <typename T, enable_if_t<!is_pyobject<T>::value, int>>
@@ -1806,7 +1806,7 @@ template <typename T> enable_if_t<cast_is_temporary_value_reference<T>::value, T
     pybind11_fail("Internal error: cast_safe fallback invoked"); }
 template <> inline void cast_safe<void>(object &&) {}
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 template <return_value_policy policy = return_value_policy::automatic_reference>
 tuple make_tuple() { return tuple(0); }
@@ -1914,7 +1914,7 @@ inline namespace literals {
 constexpr arg operator"" _a(const char *name, size_t) { return arg(name); }
 }
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 // forward declaration (definition in attr.h)
 struct function_record;
@@ -2185,7 +2185,7 @@ object object_api<Derived>::call(Args &&...args) const {
     return operator()<policy>(std::forward<Args>(args)...);
 }
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 #define PYBIND11_MAKE_OPAQUE(...) \
     namespace pybind11 { namespace detail { \
@@ -2196,4 +2196,4 @@ NAMESPACE_END(detail)
 /// typedef, e.g.: `PYBIND11_OVERLOAD(PYBIND11_TYPE(ReturnType<A, B>), PYBIND11_TYPE(Parent<C, D>), f, arg)`
 #define PYBIND11_TYPE(...) __VA_ARGS__
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/chrono.h b/include/pybind11/chrono.h
index ea777e6965..6b9ab9b82a 100644
--- a/include/pybind11/chrono.h
+++ b/include/pybind11/chrono.h
@@ -27,8 +27,8 @@
 #define PyDateTime_DELTA_GET_MICROSECONDS(o) (((PyDateTime_Delta*)o)->microseconds)
 #endif
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <typename type> class duration_caster {
 public:
@@ -180,5 +180,5 @@ template <typename Rep, typename Period> class type_caster<std::chrono::duration
 : public duration_caster<std::chrono::duration<Rep, Period>> {
 };
 
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/complex.h b/include/pybind11/complex.h
index 3f89638571..f8327eb373 100644
--- a/include/pybind11/complex.h
+++ b/include/pybind11/complex.h
@@ -17,7 +17,7 @@
 #  undef I
 #endif
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 template <typename T> struct format_descriptor<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
     static constexpr const char c = format_descriptor<T>::c;
@@ -32,7 +32,7 @@ template <typename T> constexpr const char format_descriptor<
 
 #endif
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <typename T> struct is_fmt_numeric<std::complex<T>, detail::enable_if_t<std::is_floating_point<T>::value>> {
     static constexpr bool value = true;
@@ -61,5 +61,5 @@ template <typename T> class type_caster<std::complex<T>> {
 
     PYBIND11_TYPE_CASTER(std::complex<T>, _("complex"));
 };
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/class.h b/include/pybind11/detail/class.h
index f6b89c20e1..d58f04e612 100644
--- a/include/pybind11/detail/class.h
+++ b/include/pybind11/detail/class.h
@@ -12,8 +12,8 @@
 #include "../attr.h"
 #include "../options.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if PY_VERSION_HEX >= 0x03030000 && !defined(PYPY_VERSION)
 #  define PYBIND11_BUILTIN_QUALNAME
@@ -664,5 +664,5 @@ inline PyObject* make_new_python_type(const type_record &rec) {
     return (PyObject *) type;
 }
 
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index f4840daef6..8b609e7260 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -9,12 +9,8 @@
 
 #pragma once
 
-#if !defined(NAMESPACE_BEGIN)
-#  define NAMESPACE_BEGIN(name) namespace name {
-#endif
-#if !defined(NAMESPACE_END)
-#  define NAMESPACE_END(name) }
-#endif
+#define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
+#define PYBIND11_NAMESPACE_END(name) }
 
 // Robust support for some features and loading modules compiled against different pybind versions
 // requires forcing hidden visibility on pybind code, so we enforce this by setting the attribute on
@@ -325,7 +321,7 @@ extern "C" {
     void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &variable)
 
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 using ssize_t = Py_ssize_t;
 using size_t  = std::size_t;
@@ -382,7 +378,7 @@ enum class return_value_policy : uint8_t {
     reference_internal
 };
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 inline static constexpr int log2(size_t n, int k = 0) { return (n <= 1) ? k : log2(n >> 1, k + 1); }
 
@@ -560,7 +556,7 @@ template <typename T, typename... Ts>
 constexpr size_t constexpr_sum(T n, Ts... ns) { return size_t{n} + constexpr_sum(ns...); }
 #endif
 
-NAMESPACE_BEGIN(constexpr_impl)
+PYBIND11_NAMESPACE_BEGIN(constexpr_impl)
 /// Implementation details for constexpr functions
 constexpr int first(int i) { return i; }
 template <typename T, typename... Ts>
@@ -569,7 +565,7 @@ constexpr int first(int i, T v, Ts... vs) { return v ? i : first(i + 1, vs...);
 constexpr int last(int /*i*/, int result) { return result; }
 template <typename T, typename... Ts>
 constexpr int last(int i, int result, T v, Ts... vs) { return last(i + 1, v ? i : result, vs...); }
-NAMESPACE_END(constexpr_impl)
+PYBIND11_NAMESPACE_END(constexpr_impl)
 
 /// Return the index of the first type in Ts which satisfies Predicate<T>.  Returns sizeof...(Ts) if
 /// none match.
@@ -683,7 +679,7 @@ using expand_side_effects = bool[];
 #define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) pybind11::detail::expand_side_effects{ ((PATTERN), void(), false)..., false }
 #endif
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /// C++ bindings of builtin Python exceptions
 class builtin_exception : public std::runtime_error {
@@ -715,7 +711,7 @@ PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used in
 
 template <typename T, typename SFINAE = void> struct format_descriptor { };
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 // Returns the index of the given type in the type char array below, and in the list in numpy.h
 // The order here is: bool; 8 ints ((signed,unsigned)x(8,16,32,64)bits); float,double,long double;
 // complex float,double,long double.  Note that the long double types only participate when long
@@ -728,7 +724,7 @@ template <typename T> struct is_fmt_numeric<T, enable_if_t<std::is_arithmetic<T>
         std::is_integral<T>::value ? detail::log2(sizeof(T))*2 + std::is_unsigned<T>::value : 8 + (
         std::is_same<T, double>::value ? 1 : std::is_same<T, long double>::value ? 2 : 0));
 };
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 template <typename T> struct format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>> {
     static constexpr const char c = "?bBhHiIqQfdg"[detail::is_fmt_numeric<T>::index];
@@ -753,7 +749,7 @@ struct error_scope {
 /// Dummy destructor wrapper that can be used to expose classes with a private destructor
 struct nodelete { template <typename T> void operator()(T*) { } };
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename... Args>
 struct overload_cast_impl {
     constexpr overload_cast_impl() {} // MSVC 2015 needs this
@@ -770,7 +766,7 @@ struct overload_cast_impl {
     constexpr auto operator()(Return (Class::*pmf)(Args...) const, std::true_type) const noexcept
                               -> decltype(pmf) { return pmf; }
 };
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 // overload_cast requires variable templates: C++14
 #if defined(PYBIND11_CPP14)
@@ -795,7 +791,7 @@ template <typename... Args> struct overload_cast {
 };
 #endif // overload_cast
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Adaptor for converting arbitrary container arguments into a vector; implicitly convertible from
 // any standard container (or C-style array) supporting std::begin/std::end, any singleton
@@ -834,8 +830,8 @@ class any_container {
     const std::vector<T> *operator->() const { return &v; }
 };
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/descr.h b/include/pybind11/detail/descr.h
index 8d404e5346..92720cd562 100644
--- a/include/pybind11/detail/descr.h
+++ b/include/pybind11/detail/descr.h
@@ -11,8 +11,8 @@
 
 #include "common.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if !defined(_MSC_VER)
 #  define PYBIND11_DESCR_CONSTEXPR static constexpr
@@ -96,5 +96,5 @@ constexpr descr<N + 2, Ts...> type_descr(const descr<N, Ts...> &descr) {
     return _("{") + descr + _("}");
 }
 
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/init.h b/include/pybind11/detail/init.h
index acfe00bdb7..35b95bcfae 100644
--- a/include/pybind11/detail/init.h
+++ b/include/pybind11/detail/init.h
@@ -11,8 +11,8 @@
 
 #include "class.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <>
 class type_caster<value_and_holder> {
@@ -30,7 +30,7 @@ class type_caster<value_and_holder> {
     value_and_holder *value = nullptr;
 };
 
-NAMESPACE_BEGIN(initimpl)
+PYBIND11_NAMESPACE_BEGIN(initimpl)
 
 inline void no_nullptr(void *ptr) {
     if (!ptr) throw type_error("pybind11::init(): factory function returned nullptr");
@@ -330,6 +330,6 @@ struct pickle_factory<Get, Set, RetState(Self), NewInstance(ArgState)> {
     }
 };
 
-NAMESPACE_END(initimpl)
-NAMESPACE_END(detail)
-NAMESPACE_END(pybind11)
+PYBIND11_NAMESPACE_END(initimpl)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(pybind11)
diff --git a/include/pybind11/detail/internals.h b/include/pybind11/detail/internals.h
index 166a18a32f..cf40e9fe99 100644
--- a/include/pybind11/detail/internals.h
+++ b/include/pybind11/detail/internals.h
@@ -11,8 +11,8 @@
 
 #include "../pytypes.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 // Forward declarations
 inline PyTypeObject *make_static_property_type();
 inline PyTypeObject *make_default_metaclass();
@@ -317,7 +317,7 @@ const char *c_str(Args &&...args) {
     return strings.front().c_str();
 }
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /// Returns a named pointer that is shared among all extension modules (using the same
 /// pybind11 version) running in the current interpreter. Names starting with underscores
@@ -349,4 +349,4 @@ T &get_or_create_shared_data(const std::string &name) {
     return *ptr;
 }
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/detail/typeid.h b/include/pybind11/detail/typeid.h
index 9c8a4fc69a..148889ffef 100644
--- a/include/pybind11/detail/typeid.h
+++ b/include/pybind11/detail/typeid.h
@@ -18,8 +18,8 @@
 
 #include "common.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 /// Erase all occurrences of a substring
 inline void erase_all(std::string &string, const std::string &search) {
     for (size_t pos = 0;;) {
@@ -43,7 +43,7 @@ PYBIND11_NOINLINE inline void clean_type_id(std::string &name) {
 #endif
     detail::erase_all(name, "pybind11::");
 }
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /// Return a string representation of a C++ type
 template <typename T> static std::string type_id() {
@@ -52,4 +52,4 @@ template <typename T> static std::string type_id() {
     return name;
 }
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/eigen.h b/include/pybind11/eigen.h
index d963d9650b..22139def60 100644
--- a/include/pybind11/eigen.h
+++ b/include/pybind11/eigen.h
@@ -41,14 +41,14 @@
 // of matrices seems highly undesirable.
 static_assert(EIGEN_VERSION_AT_LEAST(3,2,7), "Eigen support in pybind11 requires Eigen >= 3.2.7");
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 // Provide a convenience alias for easier pass-by-ref usage with fully dynamic strides:
 using EigenDStride = Eigen::Stride<Eigen::Dynamic, Eigen::Dynamic>;
 template <typename MatrixType> using EigenDRef = Eigen::Ref<MatrixType, 0, EigenDStride>;
 template <typename MatrixType> using EigenDMap = Eigen::Map<MatrixType, 0, EigenDStride>;
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 #if EIGEN_VERSION_AT_LEAST(3,3,0)
 using EigenIndex = Eigen::Index;
@@ -597,8 +597,8 @@ struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
             + npy_format_descriptor<Scalar>::name + _("]"));
 };
 
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
 #if defined(__GNUG__) || defined(__clang__)
 #  pragma GCC diagnostic pop
diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index f814c783e7..3258e15763 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -66,8 +66,8 @@
     void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &variable)
 
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Python 2.7/3.x compatible version of `PyImport_AppendInittab` and error checks.
 struct embedded_module {
@@ -86,7 +86,7 @@ struct embedded_module {
     }
 };
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /** \rst
     Initialize the Python interpreter. No other pybind11 or CPython API functions can be
@@ -199,4 +199,4 @@ class scoped_interpreter {
     bool is_valid = true;
 };
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/eval.h b/include/pybind11/eval.h
index 422e629f5b..ba82cf42ae 100644
--- a/include/pybind11/eval.h
+++ b/include/pybind11/eval.h
@@ -13,7 +13,7 @@
 
 #include "pybind11.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 enum eval_mode {
     /// Evaluate a string containing an isolated expression
@@ -129,4 +129,4 @@ object eval_file(str fname, object global = globals(), object local = object())
 }
 #endif
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h
index f8bda64831..57b6cd210f 100644
--- a/include/pybind11/functional.h
+++ b/include/pybind11/functional.h
@@ -12,8 +12,8 @@
 #include "pybind11.h"
 #include <functional>
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <typename Return, typename... Args>
 struct type_caster<std::function<Return(Args...)>> {
@@ -97,5 +97,5 @@ struct type_caster<std::function<Return(Args...)>> {
                                + make_caster<retval_type>::name + _("]"));
 };
 
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/iostream.h b/include/pybind11/iostream.h
index c43b7c93a6..eaf92dfa49 100644
--- a/include/pybind11/iostream.h
+++ b/include/pybind11/iostream.h
@@ -17,8 +17,8 @@
 #include <memory>
 #include <iostream>
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Buffer that writes to Python instead of C++
 class pythonbuf : public std::streambuf {
@@ -72,7 +72,7 @@ class pythonbuf : public std::streambuf {
     }
 };
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 
 /** \rst
@@ -144,7 +144,7 @@ class scoped_estream_redirect : public scoped_ostream_redirect {
 };
 
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 // Class to redirect output as a context manager. C++ backend.
 class OstreamRedirect {
@@ -170,7 +170,7 @@ class OstreamRedirect {
     }
 };
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /** \rst
     This is a helper function to add a C++ redirect context manager to Python
@@ -206,4 +206,4 @@ inline class_<detail::OstreamRedirect> add_ostream_redirect(module m, std::strin
         .def("__exit__", [](detail::OstreamRedirect &self_, args) { self_.exit(); });
 }
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 49a1e4f5e9..d322c01351 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -35,11 +35,11 @@
    upon the library user. */
 static_assert(sizeof(ssize_t) == sizeof(Py_intptr_t), "ssize_t != Py_intptr_t");
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 class array; // Forward declaration
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <> struct handle_type_name<array> { static constexpr auto name = _("numpy.ndarray"); };
 
@@ -442,7 +442,7 @@ struct type_caster<unchecked_reference<T, Dim>> {
 template <typename T, ssize_t Dim>
 struct type_caster<unchecked_mutable_reference<T, Dim>> : type_caster<unchecked_reference<T, Dim>> {};
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 class dtype : public object {
 public:
@@ -979,7 +979,7 @@ struct format_descriptor<T, detail::enable_if_t<detail::array_info<T>::is_array>
     }
 };
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename T, int ExtraFlags>
 struct pyobject_caster<array_t<T, ExtraFlags>> {
     using type = array_t<T, ExtraFlags>;
@@ -1608,7 +1608,7 @@ template <typename T, int Flags> struct handle_type_name<array_t<T, Flags>> {
     static constexpr auto name = _("numpy.ndarray[") + npy_format_descriptor<T>::name + _("]");
 };
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 // Vanilla pointer vectorizer:
 template <typename Return, typename... Args>
@@ -1638,7 +1638,7 @@ Helper vectorize(Return (Class::*f)(Args...) const) {
     return Helper(std::mem_fn(f));
 }
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
 #if defined(_MSC_VER)
 #pragma warning(pop)
diff --git a/include/pybind11/operators.h b/include/pybind11/operators.h
index 293d5abd29..086cb4cfd8 100644
--- a/include/pybind11/operators.h
+++ b/include/pybind11/operators.h
@@ -18,8 +18,8 @@
 #  pragma warning(disable: 4127) // warning C4127: Conditional expression is constant
 #endif
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Enumeration with all supported operator types
 enum op_id : int {
@@ -160,13 +160,13 @@ PYBIND11_UNARY_OPERATOR(float,      float_,       (double) l)
 #undef PYBIND11_BINARY_OPERATOR
 #undef PYBIND11_INPLACE_OPERATOR
 #undef PYBIND11_UNARY_OPERATOR
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 using detail::self;
 // Add named operators so that they are accessible via `py::`.
 using detail::hash;
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
 #if defined(_MSC_VER)
 #  pragma warning(pop)
diff --git a/include/pybind11/options.h b/include/pybind11/options.h
index cc1e1f6f0f..d74db1c68d 100644
--- a/include/pybind11/options.h
+++ b/include/pybind11/options.h
@@ -11,7 +11,7 @@
 
 #include "detail/common.h"
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 class options {
 public:
@@ -62,4 +62,4 @@ class options {
     state previous_state;
 };
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 45828dba89..ee28705245 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -50,7 +50,7 @@
 #  include <cxxabi.h>
 #endif
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /// Wraps an arbitrary C++ function/method/lambda function/.. into a callable Python object
 class cpp_function : public function {
@@ -909,7 +909,7 @@ inline dict globals() {
     return reinterpret_borrow<dict>(p ? p : module::import("__main__").attr("__dict__").ptr());
 }
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 /// Generic support for creating new Python heap types
 class generic_type : public object {
     template <typename...> friend class class_;
@@ -1047,7 +1047,7 @@ inline void call_operator_delete(void *p, size_t s, size_t a) {
     #endif
 }
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /// Given a pointer to a member function, cast it to its `Derived` version.
 /// Forward everything else unchanged.
@@ -1425,7 +1425,7 @@ detail::initimpl::pickle_factory<GetState, SetState> pickle(GetState &&g, SetSta
     return {std::forward<GetState>(g), std::forward<SetState>(s)};
 }
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 struct enum_base {
     enum_base(handle base, handle parent) : m_base(base), m_parent(parent) { }
 
@@ -1576,7 +1576,7 @@ struct enum_base {
     handle m_parent;
 };
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /// Binds C++ enumerations and enumeration classes to Python
 template <typename Type> class enum_ : public class_<Type> {
@@ -1628,7 +1628,7 @@ template <typename Type> class enum_ : public class_<Type> {
     detail::enum_base m_base;
 };
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 
 inline void keep_alive_impl(handle nurse, handle patient) {
@@ -1698,7 +1698,7 @@ struct iterator_state {
     bool first_or_done;
 };
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /// Makes a python iterator from a first and past-the-end C++ InputIterator.
 template <return_value_policy Policy = return_value_policy::reference_internal,
@@ -1831,13 +1831,13 @@ class exception : public object {
     }
 };
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 // Returns a reference to a function-local static exception object used in the simple
 // register_exception approach below.  (It would be simpler to have the static local variable
 // directly in register_exception, but that makes clang <3.5 segfault - issue #1349).
 template <typename CppException>
 exception<CppException> &get_exception_object() { static exception<CppException> ex; return ex; }
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /**
  * Registers a Python exception in `m` of the given `name` and installs an exception translator to
@@ -1863,7 +1863,7 @@ exception<CppException> &register_exception(handle scope,
     return ex;
 }
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 PYBIND11_NOINLINE inline void print(tuple args, dict kwargs) {
     auto strings = tuple(args.size());
     for (size_t i = 0; i < args.size(); ++i) {
@@ -1894,7 +1894,7 @@ PYBIND11_NOINLINE inline void print(tuple args, dict kwargs) {
     if (kwargs.contains("flush") && kwargs["flush"].cast<bool>())
         file.attr("flush")();
 }
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 template <return_value_policy policy = return_value_policy::automatic_reference, typename... Args>
 void print(Args &&...args) {
@@ -2203,7 +2203,7 @@ template <class T> function get_overload(const T *this_ptr, const char *name) {
 #define PYBIND11_OVERLOAD_PURE(ret_type, cname, fn, ...) \
     PYBIND11_OVERLOAD_PURE_NAME(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), #fn, fn, __VA_ARGS__)
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
 #if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
 #  pragma warning(pop)
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 6cf7fe173f..b2180fd3e5 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -14,14 +14,14 @@
 #include <utility>
 #include <type_traits>
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
 /* A few forward declarations */
 class handle; class object;
 class str; class iterator;
 struct arg; struct arg_v;
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 class args_proxy;
 inline bool isinstance_generic(handle obj, const std::type_info &tp);
 
@@ -158,7 +158,7 @@ class object_api : public pyobject_tag {
     bool rich_compare(object_api const &other, int value) const;
 };
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /** \rst
     Holds a reference to a Python object (no reference counting)
@@ -311,9 +311,9 @@ template <typename T> T reinterpret_borrow(handle h) { return {h, object::borrow
 \endrst */
 template <typename T> T reinterpret_steal(handle h) { return {h, object::stolen_t{}}; }
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 inline std::string error_string();
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 /// Fetch and hold an error which was already set in Python.  An instance of this is typically
 /// thrown to propagate python-side errors back through C++ which can either be caught manually or
@@ -446,7 +446,7 @@ inline ssize_t hash(handle obj) {
 
 /// @} python_builtins
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 inline handle get_function(handle value) {
     if (value) {
 #if PY_MAJOR_VERSION >= 3
@@ -520,7 +520,7 @@ class accessor : public object_api<accessor<Policy>> {
     mutable object cache;
 };
 
-NAMESPACE_BEGIN(accessor_policies)
+PYBIND11_NAMESPACE_BEGIN(accessor_policies)
 struct obj_attr {
     using key_type = object;
     static object get(handle obj, handle key) { return getattr(obj, key); }
@@ -597,7 +597,7 @@ struct tuple_item {
         }
     }
 };
-NAMESPACE_END(accessor_policies)
+PYBIND11_NAMESPACE_END(accessor_policies)
 
 /// STL iterator template used for tuple, list, sequence and dict
 template <typename Policy>
@@ -638,7 +638,7 @@ class generic_iterator : public Policy {
     friend bool operator<=(const It &a, const It &b) { return !(a > b); }
 };
 
-NAMESPACE_BEGIN(iterator_policies)
+PYBIND11_NAMESPACE_BEGIN(iterator_policies)
 /// Quick proxy class needed to implement ``operator->`` for iterators which can't return pointers
 template <typename T>
 struct arrow_proxy {
@@ -711,7 +711,7 @@ class dict_readonly {
     PyObject *key = nullptr, *value = nullptr;
     ssize_t pos = -1;
 };
-NAMESPACE_END(iterator_policies)
+PYBIND11_NAMESPACE_END(iterator_policies)
 
 #if !defined(PYPY_VERSION)
 using tuple_iterator = generic_iterator<iterator_policies::sequence_fast_readonly>;
@@ -770,7 +770,7 @@ class simple_collector;
 template <return_value_policy policy = return_value_policy::automatic_reference>
 class unpacking_collector;
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 // TODO: After the deprecated constructors are removed, this macro can be simplified by
 //       inheriting ctors: `using Parent::Parent`. It's not an option right now because
@@ -1045,7 +1045,7 @@ class bool_ : public object {
     }
 };
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 // Converts a value to the given unsigned type.  If an error occurs, you get back (Unsigned) -1;
 // otherwise you get back the unsigned long or unsigned long long value cast to (Unsigned).
 // (The distinction is critically important when casting a returned -1 error value to some other
@@ -1065,7 +1065,7 @@ Unsigned as_unsigned(PyObject *o) {
         return v == (unsigned long long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
     }
 }
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 class int_ : public object {
 public:
@@ -1409,7 +1409,7 @@ inline iterator iter(handle obj) {
 }
 /// @} python_builtins
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 template <typename D> iterator object_api<D>::begin() const { return iter(derived()); }
 template <typename D> iterator object_api<D>::end() const { return iterator::sentinel(); }
 template <typename D> item_accessor object_api<D>::operator[](handle key) const {
@@ -1490,5 +1490,5 @@ PYBIND11_MATH_OPERATOR_BINARY(operator>>=, PyNumber_InPlaceRshift)
 #undef PYBIND11_MATH_OPERATOR_UNARY
 #undef PYBIND11_MATH_OPERATOR_BINARY
 
-NAMESPACE_END(detail)
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/include/pybind11/stl.h b/include/pybind11/stl.h
index b5f7e723f4..6c2bebda87 100644
--- a/include/pybind11/stl.h
+++ b/include/pybind11/stl.h
@@ -48,8 +48,8 @@
 #  define PYBIND11_HAS_VARIANT 1
 #endif
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 /// Extracts an const lvalue reference or rvalue reference for U based on the type of T (e.g. for
 /// forwarding a container element).  Typically used indirect via forwarded_type(), below.
@@ -374,14 +374,14 @@ template <typename... Ts>
 struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> { };
 #endif
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 inline std::ostream &operator<<(std::ostream &os, const handle &obj) {
     os << (std::string) str(obj);
     return os;
 }
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
 
 #if defined(_MSC_VER)
 #pragma warning(pop)
diff --git a/include/pybind11/stl_bind.h b/include/pybind11/stl_bind.h
index da233eca99..61b94b6220 100644
--- a/include/pybind11/stl_bind.h
+++ b/include/pybind11/stl_bind.h
@@ -15,8 +15,8 @@
 #include <algorithm>
 #include <sstream>
 
-NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 /* SFINAE helper class used by 'is_comparable */
 template <typename T>  struct container_traits {
@@ -413,7 +413,7 @@ vector_buffer(Class_& cl) {
 template <typename Vector, typename Class_, typename... Args>
 enable_if_t<!detail::any_of<std::is_same<Args, buffer_protocol>...>::value> vector_buffer(Class_&) {}
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 //
 // std::vector
@@ -511,7 +511,7 @@ class_<Vector, holder_type> bind_vector(handle scope, std::string const &name, A
 // std::map, std::unordered_map
 //
 
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(detail)
 
 /* Fallback functions */
 template <typename, typename, typename... Args> void map_if_insertion_operator(const Args &...) { }
@@ -577,7 +577,7 @@ template <typename Map, typename Class_> auto map_if_insertion_operator(Class_ &
 }
 
 
-NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(detail)
 
 template <typename Map, typename holder_type = std::unique_ptr<Map>, typename... Args>
 class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&... args) {
@@ -653,4 +653,4 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args&&.
     return cl;
 }
 
-NAMESPACE_END(PYBIND11_NAMESPACE)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
diff --git a/tests/pybind11_tests.h b/tests/pybind11_tests.h
index 90963a5dea..1e47416270 100644
--- a/tests/pybind11_tests.h
+++ b/tests/pybind11_tests.h
@@ -53,13 +53,13 @@ class IncType : public UserType {
 /// Custom cast-only type that casts to a string "rvalue" or "lvalue" depending on the cast context.
 /// Used to test recursive casters (e.g. std::tuple, stl containers).
 struct RValueCaster {};
-NAMESPACE_BEGIN(pybind11)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(pybind11)
+PYBIND11_NAMESPACE_BEGIN(detail)
 template<> class type_caster<RValueCaster> {
 public:
     PYBIND11_TYPE_CASTER(RValueCaster, _("RValueCaster"));
     static handle cast(RValueCaster &&, return_value_policy, handle) { return py::str("rvalue").release(); }
     static handle cast(const RValueCaster &, return_value_policy, handle) { return py::str("lvalue").release(); }
 };
-NAMESPACE_END(detail)
-NAMESPACE_END(pybind11)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(pybind11)
diff --git a/tests/test_class.py b/tests/test_class.py
index 9807535e8e..6fa5b157a7 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -109,7 +109,10 @@ def __init__(self):
             pass
     with pytest.raises(TypeError) as exc_info:
         Python()
-    assert msg(exc_info.value) == "m.class_.Pet.__init__() must be called when overriding __init__"
+    expected = ["m.class_.Pet.__init__() must be called when overriding __init__",
+                "Pet.__init__() must be called when overriding __init__"]  # PyPy?
+    # TODO: fix PyPy error message wrt. tp_name/__qualname__?
+    assert msg(exc_info.value) in expected
 
     # Multiple bases
     class RabbitHamster(m.Rabbit, m.Hamster):
@@ -118,8 +121,9 @@ def __init__(self):
 
     with pytest.raises(TypeError) as exc_info:
         RabbitHamster()
-    expected = "m.class_.Hamster.__init__() must be called when overriding __init__"
-    assert msg(exc_info.value) == expected
+    expected = ["m.class_.Hamster.__init__() must be called when overriding __init__",
+                "Hamster.__init__() must be called when overriding __init__"]  # PyPy
+    assert msg(exc_info.value) in expected
 
 
 def test_automatic_upcasting():
diff --git a/tests/test_copy_move.cpp b/tests/test_copy_move.cpp
index 98d5e0a0bd..0f698bdf05 100644
--- a/tests/test_copy_move.cpp
+++ b/tests/test_copy_move.cpp
@@ -68,8 +68,8 @@ class CopyOnlyInt {
 
     int value;
 };
-NAMESPACE_BEGIN(pybind11)
-NAMESPACE_BEGIN(detail)
+PYBIND11_NAMESPACE_BEGIN(pybind11)
+PYBIND11_NAMESPACE_BEGIN(detail)
 template <> struct type_caster<MoveOnlyInt> {
     PYBIND11_TYPE_CASTER(MoveOnlyInt, _("MoveOnlyInt"));
     bool load(handle src, bool) { value = MoveOnlyInt(src.cast<int>()); return true; }
@@ -97,8 +97,8 @@ template <> struct type_caster<CopyOnlyInt> {
     operator CopyOnlyInt&() { return value; }
     template <typename T> using cast_op_type = pybind11::detail::cast_op_type<T>;
 };
-NAMESPACE_END(detail)
-NAMESPACE_END(pybind11)
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(pybind11)
 
 TEST_SUBMODULE(copy_move_policies, m) {
     // test_lacking_copy_ctor

From 964ab956e046d446a9e087de70d914d7a583d1de Mon Sep 17 00:00:00 2001
From: Yannick Jadoul <yannick.jadoul@belgacom.net>
Date: Fri, 10 Jul 2020 16:30:44 +0200
Subject: [PATCH 18/73] Fix DeprecationWarning about 'invalid escape sequence'
 in tools/docs Python scripts (#2281)

---
 docs/conf.py   | 2 +-
 tools/mkdoc.py | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/docs/conf.py b/docs/conf.py
index 585987ec6d..663a816d56 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -238,7 +238,7 @@
 #'pointsize': '10pt',
 
 # Additional stuff for the LaTeX preamble.
-'preamble': '\DeclareUnicodeCharacter{00A0}{}',
+'preamble': r'\DeclareUnicodeCharacter{00A0}{}',
 
 # Latex figure (float) alignment
 #'figure_align': 'htbp',
diff --git a/tools/mkdoc.py b/tools/mkdoc.py
index c85e09d4d2..cd982e0701 100755
--- a/tools/mkdoc.py
+++ b/tools/mkdoc.py
@@ -106,8 +106,8 @@ def process_comment(comment):
         result = result2
 
     # Doxygen tags
-    cpp_group = '([\w:]+)'
-    param_group = '([\[\w:\]]+)'
+    cpp_group = r'([\w:]+)'
+    param_group = r'([\[\w:\]]+)'
 
     s = result
     s = re.sub(r'\\c\s+%s' % cpp_group, r'``\1``', s)

From b2f52225fa3dd546ea8475eeee397d5c1342a32a Mon Sep 17 00:00:00 2001
From: Boris Staletic <boris.staletic@gmail.com>
Date: Fri, 10 Jul 2020 16:31:03 +0200
Subject: [PATCH 19/73] Rename embedded_module object's name (#2282)

This avoids a potential conflict with names in the same scope of the
same name as the embedded module, like namespaces or other global
variables.

Fixes #2172
---
 include/pybind11/embed.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/embed.h b/include/pybind11/embed.h
index 3258e15763..eae86c714c 100644
--- a/include/pybind11/embed.h
+++ b/include/pybind11/embed.h
@@ -61,7 +61,8 @@
         }                                                                     \
     }                                                                         \
     PYBIND11_EMBEDDED_MODULE_IMPL(name)                                       \
-    pybind11::detail::embedded_module name(PYBIND11_TOSTRING(name),           \
+    pybind11::detail::embedded_module PYBIND11_CONCAT(pybind11_module_, name) \
+                              (PYBIND11_TOSTRING(name),             \
                                PYBIND11_CONCAT(pybind11_init_impl_, name));   \
     void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &variable)
 

From 8b9eb964d904c1dab33ed819497fb997f25e473b Mon Sep 17 00:00:00 2001
From: Boris Staletic <boris.staletic@gmail.com>
Date: Sat, 11 Jul 2020 17:20:22 +0200
Subject: [PATCH 20/73] Check for NULL in raw_str on Python3 (#2290)

---
 include/pybind11/pytypes.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index b2180fd3e5..6e7666b878 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -933,8 +933,8 @@ class str : public object {
     /// Return string representation -- always returns a new reference, even if already a str
     static PyObject *raw_str(PyObject *op) {
         PyObject *str_value = PyObject_Str(op);
-#if PY_MAJOR_VERSION < 3
         if (!str_value) throw error_already_set();
+#if PY_MAJOR_VERSION < 3
         PyObject *unicode = PyUnicode_FromEncodedObject(str_value, "utf-8", nullptr);
         Py_XDECREF(str_value); str_value = unicode;
 #endif

From fe1392d0895e7104aafe60f8bda17cd568d025e5 Mon Sep 17 00:00:00 2001
From: Florian Apolloner <apollo13@users.noreply.github.com>
Date: Sun, 12 Jul 2020 14:16:19 +0200
Subject: [PATCH 21/73] Silence Clang 10 compiler warnings. Fixes #2225.
 (#2294)

---
 include/pybind11/detail/common.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 8b609e7260..33805e0f91 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -676,7 +676,7 @@ inline void ignore_unused(const int *) { }
 #define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (((PATTERN), void()), ...)
 #else
 using expand_side_effects = bool[];
-#define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) pybind11::detail::expand_side_effects{ ((PATTERN), void(), false)..., false }
+#define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (void)pybind11::detail::expand_side_effects{ ((PATTERN), void(), false)..., false }
 #endif
 
 PYBIND11_NAMESPACE_END(detail)

From aa982e131d723e2e428245847c0bc75693a11569 Mon Sep 17 00:00:00 2001
From: Boris Staletic <boris.staletic@gmail.com>
Date: Sun, 12 Jul 2020 16:45:13 +0200
Subject: [PATCH 22/73] Small fixes in numpy.h (#2293)

- `PyArray_NewFromDescr_` should have been using `Py_intptr_t const *`
  - https://github.com/numpy/numpy/blob/18a6e3e505ee416ddfc617f3e9afdff5a031c2c2/numpy/core/src/multiarray/ctors.h#L5-L8
- `PyArray_GetArrayParamsFromObject_` should be using `NPY_BOOL`
  - https://github.com/numpy/numpy/blob/18a6e3e505ee416ddfc617f3e9afdff5a031c2c2/numpy/core/src/multiarray/ctors.c#L1350-L1355
  - https://docs.scipy.org/doc/numpy-1.13.0/reference/c-api.dtype.html#c.npy_bool
- `PyArray_DescrNewFromType` is at offset 96
  - https://github.com/numpy/numpy/blob/36e017194c32a53cf2965a513243cb3c348095df/numpy/core/code_generators/numpy_api.py#L141
- `array_t` constructor that takes a size and a pointer should take `ssize_t`.
  - Fixes #1599
---
 include/pybind11/numpy.h | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index d322c01351..8c390c5317 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -181,8 +181,9 @@ struct npy_api {
     unsigned int (*PyArray_GetNDArrayCFeatureVersion_)();
     PyObject *(*PyArray_DescrFromType_)(int);
     PyObject *(*PyArray_NewFromDescr_)
-        (PyTypeObject *, PyObject *, int, Py_intptr_t *,
-         Py_intptr_t *, void *, int, PyObject *);
+        (PyTypeObject *, PyObject *, int, Py_intptr_t const *,
+         Py_intptr_t const *, void *, int, PyObject *);
+    // Unused. Not removed because that affects ABI of the class.
     PyObject *(*PyArray_DescrNewFromType_)(int);
     int (*PyArray_CopyInto_)(PyObject *, PyObject *);
     PyObject *(*PyArray_NewCopy_)(PyObject *, int);
@@ -193,9 +194,10 @@ struct npy_api {
     PyObject *(*PyArray_FromAny_) (PyObject *, PyObject *, int, int, int, PyObject *);
     int (*PyArray_DescrConverter_) (PyObject *, PyObject **);
     bool (*PyArray_EquivTypes_) (PyObject *, PyObject *);
-    int (*PyArray_GetArrayParamsFromObject_)(PyObject *, PyObject *, char, PyObject **, int *,
-                                             Py_ssize_t *, PyObject **, PyObject *);
+    int (*PyArray_GetArrayParamsFromObject_)(PyObject *, PyObject *, unsigned char, PyObject **, int *,
+                                             Py_intptr_t *, PyObject **, PyObject *);
     PyObject *(*PyArray_Squeeze_)(PyObject *);
+    // Unused. Not removed because that affects ABI of the class.
     int (*PyArray_SetBaseObject_)(PyObject *, PyObject *);
     PyObject* (*PyArray_Resize_)(PyObject*, PyArray_Dims*, int, int);
 private:
@@ -211,7 +213,7 @@ struct npy_api {
         API_PyArray_CopyInto = 82,
         API_PyArray_NewCopy = 85,
         API_PyArray_NewFromDescr = 94,
-        API_PyArray_DescrNewFromType = 9,
+        API_PyArray_DescrNewFromType = 96,
         API_PyArray_DescrConverter = 174,
         API_PyArray_EquivTypes = 182,
         API_PyArray_GetArrayParamsFromObject = 278,
@@ -866,7 +868,7 @@ template <typename T, int ExtraFlags = array::forcecast> class array_t : public
                 ExtraFlags & f_style ? f_strides(*shape, itemsize()) : c_strides(*shape, itemsize()),
                 ptr, base) { }
 
-    explicit array_t(size_t count, const T *ptr = nullptr, handle base = handle())
+    explicit array_t(ssize_t count, const T *ptr = nullptr, handle base = handle())
         : array({count}, {}, ptr, base) { }
 
     constexpr ssize_t itemsize() const {

From e248869893163b95cffb4a63e899e5d933f3ef20 Mon Sep 17 00:00:00 2001
From: Kota Yamaguchi <yamaguchi_kota@cyberagent.co.jp>
Date: Thu, 16 Jul 2020 00:50:43 +0900
Subject: [PATCH 23/73] Fix undefined memoryview format (#2223)

* Fix undefined memoryview format

* Add missing <algorithm> header

* Add workaround for py27 array compatibility

* Workaround py27 memoryview behavior

* Fix memoryview constructor from buffer_info

* Workaround PyMemoryView_FromMemory availability in py27

* Fix up memoryview tests

* Update memoryview test from buffer to check signedness

* Use static factory method to create memoryview

* Remove ndim arg from memoryview::frombuffer and add tests

* Allow ndim=0 memoryview and documentation fixup

* Use void* to align to frombuffer method signature

* Add const variants of frombuffer and frommemory

* Add memory view section in doc

* Fix docs

* Add test for null buffer

* Workaround py27 nullptr behavior in test

* Rename frombuffer to from_buffer
---
 docs/Doxyfile                  |   2 +
 docs/advanced/pycpp/numpy.rst  |  42 +++++++++
 include/pybind11/buffer_info.h |  10 ++-
 include/pybind11/pytypes.h     | 150 ++++++++++++++++++++++++++++-----
 tests/test_pytypes.cpp         |  49 +++++++++++
 tests/test_pytypes.py          |  67 +++++++++++++++
 6 files changed, 293 insertions(+), 27 deletions(-)

diff --git a/docs/Doxyfile b/docs/Doxyfile
index 1b9d1297c5..24ece0d8db 100644
--- a/docs/Doxyfile
+++ b/docs/Doxyfile
@@ -18,3 +18,5 @@ ALIASES               += "endrst=\endverbatim"
 QUIET                  = YES
 WARNINGS               = YES
 WARN_IF_UNDOCUMENTED   = NO
+PREDEFINED             = DOXYGEN_SHOULD_SKIP_THIS \
+                         PY_MAJOR_VERSION=3
diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index 3d9c90cb42..aef7abe3d7 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -384,3 +384,45 @@ operation on the C++ side:
 
    py::array a = /* A NumPy array */;
    py::array b = a[py::make_tuple(0, py::ellipsis(), 0)];
+
+Memory view
+===========
+
+For a case when we simply want to provide a direct accessor to C/C++ buffer
+without a concrete class object, we can return a ``memoryview`` object. Suppose
+we wish to expose a ``memoryview`` for 2x4 uint8_t array, we can do the
+following:
+
+.. code-block:: cpp
+
+    const uint8_t buffer[] = {
+        0, 1, 2, 3,
+        4, 5, 6, 7
+    };
+    m.def("get_memoryview2d", []() {
+        return py::memoryview::from_buffer(
+            buffer,                                    // buffer pointer
+            { 2, 4 },                                  // shape (rows, cols)
+            { sizeof(uint8_t) * 4, sizeof(uint8_t) }   // strides in bytes
+        );
+    })
+
+This approach is meant for providing a ``memoryview`` for a C/C++ buffer not
+managed by Python. The user is responsible for managing the lifetime of the
+buffer. Using a ``memoryview`` created in this way after deleting the buffer in
+C++ side results in undefined behavior.
+
+We can also use ``memoryview::from_memory`` for a simple 1D contiguous buffer:
+
+.. code-block:: cpp
+
+    m.def("get_memoryview1d", []() {
+        return py::memoryview::from_memory(
+            buffer,               // buffer pointer
+            sizeof(uint8_t) * 8   // buffer size
+        );
+    })
+
+.. note::
+
+    ``memoryview::from_memory`` is not available in Python 2.
diff --git a/include/pybind11/buffer_info.h b/include/pybind11/buffer_info.h
index 0bf42880b7..8349a46b8b 100644
--- a/include/pybind11/buffer_info.h
+++ b/include/pybind11/buffer_info.h
@@ -54,7 +54,7 @@ struct buffer_info {
     explicit buffer_info(Py_buffer *view, bool ownview = true)
     : buffer_info(view->buf, view->itemsize, view->format, view->ndim,
             {view->shape, view->shape + view->ndim}, {view->strides, view->strides + view->ndim}, view->readonly) {
-        this->view = view;
+        this->m_view = view;
         this->ownview = ownview;
     }
 
@@ -73,16 +73,18 @@ struct buffer_info {
         ndim = rhs.ndim;
         shape = std::move(rhs.shape);
         strides = std::move(rhs.strides);
-        std::swap(view, rhs.view);
+        std::swap(m_view, rhs.m_view);
         std::swap(ownview, rhs.ownview);
         readonly = rhs.readonly;
         return *this;
     }
 
     ~buffer_info() {
-        if (view && ownview) { PyBuffer_Release(view); delete view; }
+        if (m_view && ownview) { PyBuffer_Release(m_view); delete m_view; }
     }
 
+    Py_buffer *view() const { return m_view; }
+    Py_buffer *&view() { return m_view; }
 private:
     struct private_ctr_tag { };
 
@@ -90,7 +92,7 @@ struct buffer_info {
                 detail::any_container<ssize_t> &&shape_in, detail::any_container<ssize_t> &&strides_in, bool readonly)
     : buffer_info(ptr, itemsize, format, ndim, std::move(shape_in), std::move(strides_in), readonly) { }
 
-    Py_buffer *view = nullptr;
+    Py_buffer *m_view = nullptr;
     bool ownview = false;
 };
 
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 6e7666b878..5152f6804a 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -1336,35 +1336,139 @@ class buffer : public object {
 
 class memoryview : public object {
 public:
-    explicit memoryview(const buffer_info& info) {
-        static Py_buffer buf { };
-        // Py_buffer uses signed sizes, strides and shape!..
-        static std::vector<Py_ssize_t> py_strides { };
-        static std::vector<Py_ssize_t> py_shape { };
-        buf.buf = info.ptr;
-        buf.itemsize = info.itemsize;
-        buf.format = const_cast<char *>(info.format.c_str());
-        buf.ndim = (int) info.ndim;
-        buf.len = info.size;
-        py_strides.clear();
-        py_shape.clear();
-        for (size_t i = 0; i < (size_t) info.ndim; ++i) {
-            py_strides.push_back(info.strides[i]);
-            py_shape.push_back(info.shape[i]);
-        }
-        buf.strides = py_strides.data();
-        buf.shape = py_shape.data();
-        buf.suboffsets = nullptr;
-        buf.readonly = info.readonly;
-        buf.internal = nullptr;
+    PYBIND11_OBJECT_CVT(memoryview, object, PyMemoryView_Check, PyMemoryView_FromObject)
 
-        m_ptr = PyMemoryView_FromBuffer(&buf);
+    /** \rst
+        Creates ``memoryview`` from ``buffer_info``.
+
+        ``buffer_info`` must be created from ``buffer::request()``. Otherwise
+        throws an exception.
+
+        For creating a ``memoryview`` from objects that support buffer protocol,
+        use ``memoryview(const object& obj)`` instead of this constructor.
+     \endrst */
+    explicit memoryview(const buffer_info& info) {
+        if (!info.view())
+            pybind11_fail("Prohibited to create memoryview without Py_buffer");
+        // Note: PyMemoryView_FromBuffer never increments obj reference.
+        m_ptr = (info.view()->obj) ?
+            PyMemoryView_FromObject(info.view()->obj) :
+            PyMemoryView_FromBuffer(info.view());
         if (!m_ptr)
             pybind11_fail("Unable to create memoryview from buffer descriptor");
     }
 
-    PYBIND11_OBJECT_CVT(memoryview, object, PyMemoryView_Check, PyMemoryView_FromObject)
+    /** \rst
+        Creates ``memoryview`` from static buffer.
+
+        This method is meant for providing a ``memoryview`` for C/C++ buffer not
+        managed by Python. The caller is responsible for managing the lifetime
+        of ``ptr`` and ``format``, which MUST outlive the memoryview constructed
+        here.
+
+        See also: Python C API documentation for `PyMemoryView_FromBuffer`_.
+
+        .. _PyMemoryView_FromBuffer: https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromBuffer
+
+        :param ptr: Pointer to the buffer.
+        :param itemsize: Byte size of an element.
+        :param format: Pointer to the null-terminated format string. For
+            homogeneous Buffers, this should be set to
+            ``format_descriptor<T>::value``.
+        :param shape: Shape of the tensor (1 entry per dimension).
+        :param strides: Number of bytes between adjacent entries (for each
+            per dimension).
+        :param readonly: Flag to indicate if the underlying storage may be
+            written to.
+     \endrst */
+    static memoryview from_buffer(
+        void *ptr, ssize_t itemsize, const char *format,
+        detail::any_container<ssize_t> shape,
+        detail::any_container<ssize_t> strides, bool readonly = false);
+
+    static memoryview from_buffer(
+        const void *ptr, ssize_t itemsize, const char *format,
+        detail::any_container<ssize_t> shape,
+        detail::any_container<ssize_t> strides) {
+        return memoryview::from_buffer(
+            const_cast<void*>(ptr), itemsize, format, shape, strides, true);
+    }
+
+    template<typename T>
+    static memoryview from_buffer(
+        T *ptr, detail::any_container<ssize_t> shape,
+        detail::any_container<ssize_t> strides, bool readonly = false) {
+        return memoryview::from_buffer(
+            reinterpret_cast<void*>(ptr), sizeof(T),
+            format_descriptor<T>::value, shape, strides, readonly);
+    }
+
+    template<typename T>
+    static memoryview from_buffer(
+        const T *ptr, detail::any_container<ssize_t> shape,
+        detail::any_container<ssize_t> strides) {
+        return memoryview::from_buffer(
+            const_cast<T*>(ptr), shape, strides, true);
+    }
+
+#if PY_MAJOR_VERSION >= 3
+    /** \rst
+        Creates ``memoryview`` from static memory.
+
+        This method is meant for providing a ``memoryview`` for C/C++ buffer not
+        managed by Python. The caller is responsible for managing the lifetime
+        of ``mem``, which MUST outlive the memoryview constructed here.
+
+        This method is not available in Python 2.
+
+        See also: Python C API documentation for `PyMemoryView_FromBuffer`_.
+
+        .. _PyMemoryView_FromMemory: https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromMemory
+     \endrst */
+    static memoryview from_memory(void *mem, ssize_t size, bool readonly = false) {
+        PyObject* ptr = PyMemoryView_FromMemory(
+            reinterpret_cast<char*>(mem), size,
+            (readonly) ? PyBUF_READ : PyBUF_WRITE);
+        if (!ptr)
+            pybind11_fail("Could not allocate memoryview object!");
+        return memoryview(object(ptr, stolen_t{}));
+    }
+
+    static memoryview from_memory(const void *mem, ssize_t size) {
+        return memoryview::from_memory(const_cast<void*>(mem), size, true);
+    }
+#endif
 };
+
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
+inline memoryview memoryview::from_buffer(
+    void *ptr, ssize_t itemsize, const char* format,
+    detail::any_container<ssize_t> shape,
+    detail::any_container<ssize_t> strides, bool readonly) {
+    size_t ndim = shape->size();
+    if (ndim != strides->size())
+        pybind11_fail("memoryview: shape length doesn't match strides length");
+    ssize_t size = ndim ? 1 : 0;
+    for (size_t i = 0; i < ndim; ++i)
+        size *= (*shape)[i];
+    Py_buffer view;
+    view.buf = ptr;
+    view.obj = nullptr;
+    view.len = size * itemsize;
+    view.readonly = static_cast<int>(readonly);
+    view.itemsize = itemsize;
+    view.format = const_cast<char*>(format);
+    view.ndim = static_cast<int>(ndim);
+    view.shape = shape->data();
+    view.strides = strides->data();
+    view.suboffsets = nullptr;
+    view.internal = nullptr;
+    PyObject* obj = PyMemoryView_FromBuffer(&view);
+    if (!obj)
+        throw error_already_set();
+    return memoryview(object(obj, stolen_t{}));
+}
+#endif  // DOXYGEN_SHOULD_SKIP_THIS
 /// @} pytypes
 
 /// \addtogroup python_builtins
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index f0d86d872c..9f7bc37dc6 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -318,4 +318,53 @@ TEST_SUBMODULE(pytypes, m) {
     m.def("test_list_slicing", [](py::list a) {
         return a[py::slice(0, -1, 2)];
     });
+
+    m.def("test_memoryview_object", [](py::buffer b) {
+        return py::memoryview(b);
+    });
+
+    m.def("test_memoryview_buffer_info", [](py::buffer b) {
+        return py::memoryview(b.request());
+    });
+
+    m.def("test_memoryview_from_buffer", [](bool is_unsigned) {
+        static const int16_t si16[] = { 3, 1, 4, 1, 5 };
+        static const uint16_t ui16[] = { 2, 7, 1, 8 };
+        if (is_unsigned)
+            return py::memoryview::from_buffer(
+                ui16, { 4 }, { sizeof(uint16_t) });
+        else
+            return py::memoryview::from_buffer(
+                si16, { 5 }, { sizeof(int16_t) });
+    });
+
+    m.def("test_memoryview_from_buffer_nativeformat", []() {
+        static const char* format = "@i";
+        static const int32_t arr[] = { 4, 7, 5 };
+        return py::memoryview::from_buffer(
+            arr, sizeof(int32_t), format, { 3 }, { sizeof(int32_t) });
+    });
+
+    m.def("test_memoryview_from_buffer_empty_shape", []() {
+        static const char* buf = "";
+        return py::memoryview::from_buffer(buf, 1, "B", { }, { });
+    });
+
+    m.def("test_memoryview_from_buffer_invalid_strides", []() {
+        static const char* buf = "\x02\x03\x04";
+        return py::memoryview::from_buffer(buf, 1, "B", { 3 }, { });
+    });
+
+    m.def("test_memoryview_from_buffer_nullptr", []() {
+        return py::memoryview::from_buffer(
+            static_cast<void*>(nullptr), 1, "B", { }, { });
+    });
+
+#if PY_MAJOR_VERSION >= 3
+    m.def("test_memoryview_from_memory", []() {
+        const char* buf = "\xff\xe1\xab\x37";
+        return py::memoryview::from_memory(
+            buf, static_cast<ssize_t>(strlen(buf)));
+    });
+#endif
 }
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 79bee87750..a8b653a114 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -278,3 +278,70 @@ def test_number_protocol():
 def test_list_slicing():
     li = list(range(100))
     assert li[::2] == m.test_list_slicing(li)
+
+
+@pytest.mark.parametrize('method, args, fmt, expected_view', [
+    (m.test_memoryview_object, (b'red',), 'B', b'red'),
+    (m.test_memoryview_buffer_info, (b'green',), 'B', b'green'),
+    (m.test_memoryview_from_buffer, (False,), 'h', [3, 1, 4, 1, 5]),
+    (m.test_memoryview_from_buffer, (True,), 'H', [2, 7, 1, 8]),
+    (m.test_memoryview_from_buffer_nativeformat, (), '@i', [4, 7, 5]),
+])
+def test_memoryview(method, args, fmt, expected_view):
+    view = method(*args)
+    assert isinstance(view, memoryview)
+    assert view.format == fmt
+    if isinstance(expected_view, bytes) or sys.version_info[0] >= 3:
+        view_as_list = list(view)
+    else:
+        # Using max to pick non-zero byte (big-endian vs little-endian).
+        view_as_list = [max([ord(c) for c in s]) for s in view]
+    assert view_as_list == list(expected_view)
+
+
+@pytest.mark.skipif(
+    not hasattr(sys, 'getrefcount'),
+    reason='getrefcount is not available')
+@pytest.mark.parametrize('method', [
+    m.test_memoryview_object,
+    m.test_memoryview_buffer_info,
+])
+def test_memoryview_refcount(method):
+    buf = b'\x0a\x0b\x0c\x0d'
+    ref_before = sys.getrefcount(buf)
+    view = method(buf)
+    ref_after = sys.getrefcount(buf)
+    assert ref_before < ref_after
+    assert list(view) == list(buf)
+
+
+def test_memoryview_from_buffer_empty_shape():
+    view = m.test_memoryview_from_buffer_empty_shape()
+    assert isinstance(view, memoryview)
+    assert view.format == 'B'
+    if sys.version_info.major < 3:
+        # Python 2 behavior is weird, but Python 3 (the future) is fine.
+        assert bytes(view).startswith(b'<memory at ')
+    else:
+        assert bytes(view) == b''
+
+
+def test_test_memoryview_from_buffer_invalid_strides():
+    with pytest.raises(RuntimeError):
+        m.test_memoryview_from_buffer_invalid_strides()
+
+
+def test_test_memoryview_from_buffer_nullptr():
+    if sys.version_info.major < 3:
+        m.test_memoryview_from_buffer_nullptr()
+    else:
+        with pytest.raises(ValueError):
+            m.test_memoryview_from_buffer_nullptr()
+
+
+@pytest.mark.skipif(sys.version_info.major < 3, reason='API not available')
+def test_memoryview_from_memory():
+    view = m.test_memoryview_from_memory()
+    assert isinstance(view, memoryview)
+    assert view.format == 'B'
+    assert bytes(view) == b'\xff\xe1\xab\x37'

From d8c7ee00a687ac369e62e2032514a93a9b413502 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henry.fredrick.schreiner@cern.ch>
Date: Mon, 20 Jul 2020 13:35:21 -0400
Subject: [PATCH 24/73] ci: GHA basic format & pre-commit (#2309)

---
 .github/workflows/format.yml          | 19 ++++++++++++++++++
 .pre-commit-config.yaml               | 28 +++++++++++++++++++++++++++
 CONTRIBUTING.md                       |  9 +++++++--
 docs/advanced/cast/index.rst          |  1 -
 docs/advanced/classes.rst             |  4 ++--
 docs/advanced/misc.rst                | 10 +++++-----
 docs/advanced/pycpp/object.rst        |  8 ++++----
 docs/benchmark.py                     |  1 +
 docs/benchmark.rst                    |  2 --
 docs/conf.py                          |  4 ++--
 docs/limitations.rst                  |  1 -
 pybind11/__init__.py                  |  1 +
 pybind11/__main__.py                  |  1 +
 pybind11/_version.py                  |  1 +
 setup.py                              |  1 +
 tests/conftest.py                     |  1 +
 tests/constructor_stats.h             |  1 -
 tests/test_async.py                   |  1 +
 tests/test_buffers.py                 |  1 +
 tests/test_builtin_casters.py         |  2 +-
 tests/test_call_policies.py           |  1 +
 tests/test_callbacks.py               |  1 +
 tests/test_chrono.py                  |  1 +
 tests/test_class.py                   |  1 +
 tests/test_cmake_build/test.py        |  1 +
 tests/test_constants_and_functions.py |  1 +
 tests/test_copy_move.py               |  1 +
 tests/test_custom_type_casters.py     |  1 +
 tests/test_docstring_options.py       |  1 +
 tests/test_eigen.py                   |  5 +++--
 tests/test_embed/test_interpreter.py  |  1 +
 tests/test_enum.py                    |  1 +
 tests/test_eval.py                    |  1 +
 tests/test_eval_call.py               |  1 +
 tests/test_exceptions.py              |  1 +
 tests/test_factory_constructors.py    |  1 +
 tests/test_gil_scoped.py              |  1 +
 tests/test_iostream.py                |  1 +
 tests/test_kwargs_and_defaults.py     |  1 +
 tests/test_local_bindings.py          |  1 +
 tests/test_methods_and_attributes.py  |  1 +
 tests/test_modules.py                 |  1 +
 tests/test_multiple_inheritance.py    |  1 +
 tests/test_numpy_array.py             |  1 +
 tests/test_numpy_dtypes.py            |  1 +
 tests/test_numpy_vectorize.py         |  1 +
 tests/test_opaque_types.py            |  1 +
 tests/test_operator_overloading.py    |  1 +
 tests/test_pickling.py                |  1 +
 tests/test_pytypes.py                 |  1 +
 tests/test_sequences_and_iterators.py |  1 +
 tests/test_smart_ptr.py               |  1 +
 tests/test_stl.py                     |  1 +
 tests/test_stl_binders.py             |  8 +++++---
 tests/test_tagbased_polymorphic.py    |  1 +
 tests/test_union.py                   |  1 +
 tests/test_virtual_functions.py       |  1 +
 tools/FindEigen3.cmake                |  1 -
 tools/libsize.py                      |  2 +-
 tools/mkdoc.py                        |  1 +
 60 files changed, 121 insertions(+), 28 deletions(-)
 create mode 100644 .github/workflows/format.yml
 create mode 100644 .pre-commit-config.yaml

diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
new file mode 100644
index 0000000000..e92f96e6ef
--- /dev/null
+++ b/.github/workflows/format.yml
@@ -0,0 +1,19 @@
+name: Format
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+    - master
+    - stable
+    - "v*"
+
+jobs:
+  pre-commit:
+    name: Format
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
+    - uses: pre-commit/action@v2.0.0
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000000..63e4c6f7d1
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,28 @@
+repos:
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v3.1.0
+  hooks:
+  - id: check-added-large-files
+  - id: check-case-conflict
+  - id: check-merge-conflict
+  - id: check-symlinks
+  - id: check-yaml
+  - id: debug-statements
+  - id: end-of-file-fixer
+  - id: mixed-line-ending
+  - id: requirements-txt-fixer
+  - id: trailing-whitespace
+  - id: fix-encoding-pragma
+
+- repo: https://github.com/Lucas-C/pre-commit-hooks
+  rev: v1.1.7
+  hooks:
+  - id: remove-tabs
+    exclude: (Makefile|debian/rules|.gitmodules)(\.in)?$
+
+- repo: https://gitlab.com/pycqa/flake8
+  rev: 3.8.2
+  hooks:
+  - id: flake8
+    additional_dependencies: [flake8-bugbear]
+    exclude: ^(docs/.*|tools/.*)$
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 01596d94f3..0997918122 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -27,11 +27,16 @@ adhere to the following rules to make the process as smooth as possible:
   do add value by themselves.
 * Add tests for any new functionality and run the test suite (``make pytest``)
   to ensure that no existing features break.
-* Please run ``flake8`` and ``tools/check-style.sh`` to check your code matches
-  the project style. (Note that ``check-style.sh`` requires ``gawk``.)
+* Please run [``pre-commit``][pre-commit] and ``tools/check-style.sh`` to check
+  your code matches the project style. (Note that ``check-style.sh`` requires
+  ``gawk``.) Use `pre-commit run --all-files` before committing (or use
+  installed-mode, check pre-commit docs) to verify your code passes before
+  pushing to save time.
 * This project has a strong focus on providing general solutions using a
   minimal amount of code, thus small pull requests are greatly preferred.
 
+[pre-commit]: https://pre-commit.com
+
 ### Licensing of contributions
 
 pybind11 is provided under a BSD-style license that can be found in the
diff --git a/docs/advanced/cast/index.rst b/docs/advanced/cast/index.rst
index 54c10570b1..724585c920 100644
--- a/docs/advanced/cast/index.rst
+++ b/docs/advanced/cast/index.rst
@@ -39,4 +39,3 @@ the last case of the above list.
    chrono
    eigen
    custom
-
diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index b3da0378c0..031484c9d0 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -82,7 +82,7 @@ helper class that is defined as follows:
 
 The macro :c:macro:`PYBIND11_OVERLOAD_PURE` should be used for pure virtual
 functions, and :c:macro:`PYBIND11_OVERLOAD` should be used for functions which have
-a default implementation.  There are also two alternate macros 
+a default implementation.  There are also two alternate macros
 :c:macro:`PYBIND11_OVERLOAD_PURE_NAME` and :c:macro:`PYBIND11_OVERLOAD_NAME` which
 take a string-valued name argument between the *Parent class* and *Name of the
 function* slots, which defines the name of function in Python. This is required
@@ -1088,7 +1088,7 @@ Binding final classes
 
 Some classes may not be appropriate to inherit from. In C++11, classes can
 use the ``final`` specifier to ensure that a class cannot be inherited from.
-The ``py::is_final`` attribute can be used to ensure that Python classes 
+The ``py::is_final`` attribute can be used to ensure that Python classes
 cannot inherit from a specified type. The underlying C++ type does not need
 to be declared final.
 
diff --git a/docs/advanced/misc.rst b/docs/advanced/misc.rst
index 5b38ec7598..7798462df7 100644
--- a/docs/advanced/misc.rst
+++ b/docs/advanced/misc.rst
@@ -218,7 +218,7 @@ collected:
 
 Both approaches also expose a potentially dangerous ``_cleanup`` attribute in
 Python, which may be undesirable from an API standpoint (a premature explicit
-call from Python might lead to undefined behavior). Yet another approach that 
+call from Python might lead to undefined behavior). Yet another approach that
 avoids this issue involves weak reference with a cleanup callback:
 
 .. code-block:: cpp
@@ -283,9 +283,9 @@ work, it is important that all lines are indented consistently, i.e.:
         ----------
     )mydelimiter");
 
-By default, pybind11 automatically generates and prepends a signature to the docstring of a function 
+By default, pybind11 automatically generates and prepends a signature to the docstring of a function
 registered with ``module::def()`` and ``class_::def()``. Sometimes this
-behavior is not desirable, because you want to provide your own signature or remove 
+behavior is not desirable, because you want to provide your own signature or remove
 the docstring completely to exclude the function from the Sphinx documentation.
 The class ``options`` allows you to selectively suppress auto-generated signatures:
 
@@ -298,8 +298,8 @@ The class ``options`` allows you to selectively suppress auto-generated signatur
         m.def("add", [](int a, int b) { return a + b; }, "A function which adds two numbers");
     }
 
-Note that changes to the settings affect only function bindings created during the 
-lifetime of the ``options`` instance. When it goes out of scope at the end of the module's init function, 
+Note that changes to the settings affect only function bindings created during the
+lifetime of the ``options`` instance. When it goes out of scope at the end of the module's init function,
 the default settings are restored to prevent unwanted side effects.
 
 .. [#f4] http://www.sphinx-doc.org
diff --git a/docs/advanced/pycpp/object.rst b/docs/advanced/pycpp/object.rst
index 117131edcb..19a226a876 100644
--- a/docs/advanced/pycpp/object.rst
+++ b/docs/advanced/pycpp/object.rst
@@ -60,7 +60,7 @@ This example obtains a reference to the Python ``Decimal`` class.
 Calling Python functions
 ========================
 
-It is also possible to call Python classes, functions and methods 
+It is also possible to call Python classes, functions and methods
 via ``operator()``.
 
 .. code-block:: cpp
@@ -75,7 +75,7 @@ via ``operator()``.
     py::object makedirs = os.attr("makedirs");
     makedirs("/tmp/path/to/somewhere");
 
-One can convert the result obtained from Python to a pure C++ version 
+One can convert the result obtained from Python to a pure C++ version
 if a ``py::class_`` or type conversion is defined.
 
 .. code-block:: cpp
@@ -99,8 +99,8 @@ Python method.
     py::print(py::str(exp_pi));
 
 In the example above ``pi.attr("exp")`` is a *bound method*: it will always call
-the method for that same instance of the class. Alternately one can create an 
-*unbound method* via the Python class (instead of instance) and pass the ``self`` 
+the method for that same instance of the class. Alternately one can create an
+*unbound method* via the Python class (instead of instance) and pass the ``self``
 object explicitly, followed by other arguments.
 
 .. code-block:: cpp
diff --git a/docs/benchmark.py b/docs/benchmark.py
index 6dc0604ea9..023477212e 100644
--- a/docs/benchmark.py
+++ b/docs/benchmark.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import random
 import os
 import time
diff --git a/docs/benchmark.rst b/docs/benchmark.rst
index 59d533df94..02c2ccde7d 100644
--- a/docs/benchmark.rst
+++ b/docs/benchmark.rst
@@ -93,5 +93,3 @@ favor.
 .. only:: latex
 
     .. image:: pybind11_vs_boost_python2.png
-
-
diff --git a/docs/conf.py b/docs/conf.py
index 663a816d56..0946f30e2e 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -130,8 +130,8 @@
 else:
     html_context = {
         'css_files': [
-            '//media.readthedocs.org/css/sphinx_rtd_theme.css',            
-            '//media.readthedocs.org/css/readthedocs-doc-embed.css',    
+            '//media.readthedocs.org/css/sphinx_rtd_theme.css',
+            '//media.readthedocs.org/css/readthedocs-doc-embed.css',
             '_static/theme_overrides.css'
         ]
     }
diff --git a/docs/limitations.rst b/docs/limitations.rst
index a1a4f1affa..59474f82fd 100644
--- a/docs/limitations.rst
+++ b/docs/limitations.rst
@@ -17,4 +17,3 @@ These features could be implemented but would lead to a significant increase in
 complexity. I've decided to draw the line here to keep this project simple and
 compact. Users who absolutely require these features are encouraged to fork
 pybind11.
-
diff --git a/pybind11/__init__.py b/pybind11/__init__.py
index 4b1de3efaa..5b2f83d5cd 100644
--- a/pybind11/__init__.py
+++ b/pybind11/__init__.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from ._version import version_info, __version__  # noqa: F401 imported but unused
 
 
diff --git a/pybind11/__main__.py b/pybind11/__main__.py
index 89b263a8ad..5e393cc8f1 100644
--- a/pybind11/__main__.py
+++ b/pybind11/__main__.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from __future__ import print_function
 
 import argparse
diff --git a/pybind11/_version.py b/pybind11/_version.py
index d0eb659bd5..1f2f254ce5 100644
--- a/pybind11/_version.py
+++ b/pybind11/_version.py
@@ -1,2 +1,3 @@
+# -*- coding: utf-8 -*-
 version_info = (2, 5, 'dev1')
 __version__ = '.'.join(map(str, version_info))
diff --git a/setup.py b/setup.py
index 668b56a5b0..577a6b6c37 100644
--- a/setup.py
+++ b/setup.py
@@ -1,4 +1,5 @@
 #!/usr/bin/env python
+# -*- coding: utf-8 -*-
 
 # Setup script for PyPI; use CMakeFile.txt to build extension modules
 
diff --git a/tests/conftest.py b/tests/conftest.py
index 58ebecaf9c..d317c49dbc 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 """pytest configuration
 
 Extends output capture as needed by pybind11: ignore constructors, optional unordered lines.
diff --git a/tests/constructor_stats.h b/tests/constructor_stats.h
index 431e5acef9..abfaf91614 100644
--- a/tests/constructor_stats.h
+++ b/tests/constructor_stats.h
@@ -273,4 +273,3 @@ template <class T, typename... Values> void print_values(T *inst, Values &&...va
     print_constr_details(inst, ":", values...);
     track_values(inst, values...);
 }
-
diff --git a/tests/test_async.py b/tests/test_async.py
index e1c959d602..e9292c9d9c 100644
--- a/tests/test_async.py
+++ b/tests/test_async.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import asyncio
 import pytest
 from pybind11_tests import async_module as m
diff --git a/tests/test_buffers.py b/tests/test_buffers.py
index bf7aaed70d..e264311d7c 100644
--- a/tests/test_buffers.py
+++ b/tests/test_buffers.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import io
 import struct
 import sys
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 91422588cf..9a49ffab54 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -1,4 +1,4 @@
-# Python < 3 needs this: coding=utf-8
+# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import builtin_casters as m
diff --git a/tests/test_call_policies.py b/tests/test_call_policies.py
index 7c835599c2..0e3230c573 100644
--- a/tests/test_call_policies.py
+++ b/tests/test_call_policies.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import call_policies as m
 from pybind11_tests import ConstructorStats
diff --git a/tests/test_callbacks.py b/tests/test_callbacks.py
index 6439c8e72a..d5d0e045d2 100644
--- a/tests/test_callbacks.py
+++ b/tests/test_callbacks.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import callbacks as m
 from threading import Thread
diff --git a/tests/test_chrono.py b/tests/test_chrono.py
index 55c9544065..f1817e44f6 100644
--- a/tests/test_chrono.py
+++ b/tests/test_chrono.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from pybind11_tests import chrono as m
 import datetime
 
diff --git a/tests/test_class.py b/tests/test_class.py
index 6fa5b157a7..c38a5e8ce8 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import class_ as m
diff --git a/tests/test_cmake_build/test.py b/tests/test_cmake_build/test.py
index 1467a61dc0..87ed5135ff 100644
--- a/tests/test_cmake_build/test.py
+++ b/tests/test_cmake_build/test.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import sys
 import test_cmake_build
 
diff --git a/tests/test_constants_and_functions.py b/tests/test_constants_and_functions.py
index 472682d619..36b1aa64b1 100644
--- a/tests/test_constants_and_functions.py
+++ b/tests/test_constants_and_functions.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from pybind11_tests import constants_and_functions as m
 
 
diff --git a/tests/test_copy_move.py b/tests/test_copy_move.py
index 0e671d9696..6b53993a91 100644
--- a/tests/test_copy_move.py
+++ b/tests/test_copy_move.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import copy_move_policies as m
 
diff --git a/tests/test_custom_type_casters.py b/tests/test_custom_type_casters.py
index d3daa2c394..9475c45168 100644
--- a/tests/test_custom_type_casters.py
+++ b/tests/test_custom_type_casters.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import custom_type_casters as m
 
diff --git a/tests/test_docstring_options.py b/tests/test_docstring_options.py
index 0dbca609ef..80ade0f158 100644
--- a/tests/test_docstring_options.py
+++ b/tests/test_docstring_options.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from pybind11_tests import docstring_options as m
 
 
diff --git a/tests/test_eigen.py b/tests/test_eigen.py
index d836398a0f..ae868da513 100644
--- a/tests/test_eigen.py
+++ b/tests/test_eigen.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import ConstructorStats
 
@@ -143,7 +144,7 @@ def test_nonunit_stride_from_python():
 
     counting_3d = np.arange(27.0, dtype=np.float32).reshape((3, 3, 3))
     slices = [counting_3d[0, :, :], counting_3d[:, 0, :], counting_3d[:, :, 0]]
-    for slice_idx, ref_mat in enumerate(slices):
+    for ref_mat in slices:
         np.testing.assert_array_equal(m.double_mat_cm(ref_mat), 2.0 * ref_mat)
         np.testing.assert_array_equal(m.double_mat_rm(ref_mat), 2.0 * ref_mat)
 
@@ -172,7 +173,7 @@ def test_negative_stride_from_python(msg):
     counting_3d = np.arange(27.0, dtype=np.float32).reshape((3, 3, 3))
     counting_3d = counting_3d[::-1, ::-1, ::-1]
     slices = [counting_3d[0, :, :], counting_3d[:, 0, :], counting_3d[:, :, 0]]
-    for slice_idx, ref_mat in enumerate(slices):
+    for ref_mat in slices:
         np.testing.assert_array_equal(m.double_mat_cm(ref_mat), 2.0 * ref_mat)
         np.testing.assert_array_equal(m.double_mat_rm(ref_mat), 2.0 * ref_mat)
 
diff --git a/tests/test_embed/test_interpreter.py b/tests/test_embed/test_interpreter.py
index 26a0479216..6174ede446 100644
--- a/tests/test_embed/test_interpreter.py
+++ b/tests/test_embed/test_interpreter.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from widget_module import Widget
 
 
diff --git a/tests/test_enum.py b/tests/test_enum.py
index 7fe9b618d6..bfaa193e9b 100644
--- a/tests/test_enum.py
+++ b/tests/test_enum.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import enums as m
 
diff --git a/tests/test_eval.py b/tests/test_eval.py
index 94228e7d27..66bec55f8b 100644
--- a/tests/test_eval.py
+++ b/tests/test_eval.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import os
 import pytest
 from pybind11_tests import eval_ as m
diff --git a/tests/test_eval_call.py b/tests/test_eval_call.py
index 53c7e721fe..d42a0a6d30 100644
--- a/tests/test_eval_call.py
+++ b/tests/test_eval_call.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 # This file is called from 'test_eval.py'
 
 if 'call_test2' in locals():
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index ac2b3603ec..053e7d4a28 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import exceptions as m
diff --git a/tests/test_factory_constructors.py b/tests/test_factory_constructors.py
index 78a3910ada..49e6f4f331 100644
--- a/tests/test_factory_constructors.py
+++ b/tests/test_factory_constructors.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 import re
 
diff --git a/tests/test_gil_scoped.py b/tests/test_gil_scoped.py
index 1548337ccc..1307712ad3 100644
--- a/tests/test_gil_scoped.py
+++ b/tests/test_gil_scoped.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import multiprocessing
 import threading
 from pybind11_tests import gil_scoped as m
diff --git a/tests/test_iostream.py b/tests/test_iostream.py
index 27095b2705..7ac4fcece0 100644
--- a/tests/test_iostream.py
+++ b/tests/test_iostream.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from pybind11_tests import iostream as m
 import sys
 
diff --git a/tests/test_kwargs_and_defaults.py b/tests/test_kwargs_and_defaults.py
index bad6636cb4..6c72a93689 100644
--- a/tests/test_kwargs_and_defaults.py
+++ b/tests/test_kwargs_and_defaults.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import kwargs_and_defaults as m
 
diff --git a/tests/test_local_bindings.py b/tests/test_local_bindings.py
index be841a70c3..913cf0ee5b 100644
--- a/tests/test_local_bindings.py
+++ b/tests/test_local_bindings.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import local_bindings as m
diff --git a/tests/test_methods_and_attributes.py b/tests/test_methods_and_attributes.py
index 8bda7a8b20..25a01c7186 100644
--- a/tests/test_methods_and_attributes.py
+++ b/tests/test_methods_and_attributes.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import methods_and_attributes as m
 from pybind11_tests import ConstructorStats
diff --git a/tests/test_modules.py b/tests/test_modules.py
index 2552838c2b..7e21005245 100644
--- a/tests/test_modules.py
+++ b/tests/test_modules.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from pybind11_tests import modules as m
 from pybind11_tests.modules import subsubmodule as ms
 from pybind11_tests import ConstructorStats
diff --git a/tests/test_multiple_inheritance.py b/tests/test_multiple_inheritance.py
index 7a6e4a0852..bb602f84bb 100644
--- a/tests/test_multiple_inheritance.py
+++ b/tests/test_multiple_inheritance.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import ConstructorStats
 from pybind11_tests import multiple_inheritance as m
diff --git a/tests/test_numpy_array.py b/tests/test_numpy_array.py
index 55571964d0..2c977cd62e 100644
--- a/tests/test_numpy_array.py
+++ b/tests/test_numpy_array.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import numpy_array as m
 
diff --git a/tests/test_numpy_dtypes.py b/tests/test_numpy_dtypes.py
index 2e63885174..d173435fe6 100644
--- a/tests/test_numpy_dtypes.py
+++ b/tests/test_numpy_dtypes.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import re
 import pytest
 from pybind11_tests import numpy_dtypes as m
diff --git a/tests/test_numpy_vectorize.py b/tests/test_numpy_vectorize.py
index c078ee7cf0..bd3c01347c 100644
--- a/tests/test_numpy_vectorize.py
+++ b/tests/test_numpy_vectorize.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import numpy_vectorize as m
 
diff --git a/tests/test_opaque_types.py b/tests/test_opaque_types.py
index 6b3802fdba..3f2392775d 100644
--- a/tests/test_opaque_types.py
+++ b/tests/test_opaque_types.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import opaque_types as m
 from pybind11_tests import ConstructorStats, UserType
diff --git a/tests/test_operator_overloading.py b/tests/test_operator_overloading.py
index 1cee29889c..6c927228ce 100644
--- a/tests/test_operator_overloading.py
+++ b/tests/test_operator_overloading.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import operators as m
 from pybind11_tests import ConstructorStats
diff --git a/tests/test_pickling.py b/tests/test_pickling.py
index 5ae05aaa0c..58d67a6339 100644
--- a/tests/test_pickling.py
+++ b/tests/test_pickling.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import pickling as m
 
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index a8b653a114..5d2ccf8fd1 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from __future__ import division
 import pytest
 import sys
diff --git a/tests/test_sequences_and_iterators.py b/tests/test_sequences_and_iterators.py
index d839dbef6a..8f6c0c4bbd 100644
--- a/tests/test_sequences_and_iterators.py
+++ b/tests/test_sequences_and_iterators.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import sequences_and_iterators as m
 from pybind11_tests import ConstructorStats
diff --git a/tests/test_smart_ptr.py b/tests/test_smart_ptr.py
index d275b3dc9b..c9267f6878 100644
--- a/tests/test_smart_ptr.py
+++ b/tests/test_smart_ptr.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 from pybind11_tests import smart_ptr as m
 from pybind11_tests import ConstructorStats
diff --git a/tests/test_stl.py b/tests/test_stl.py
index 613796356f..141b3e8492 100644
--- a/tests/test_stl.py
+++ b/tests/test_stl.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import stl as m
diff --git a/tests/test_stl_binders.py b/tests/test_stl_binders.py
index c1264c01f2..27b326f070 100644
--- a/tests/test_stl_binders.py
+++ b/tests/test_stl_binders.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 import sys
 from pybind11_tests import stl_binders as m
@@ -222,7 +223,8 @@ def test_noncopyable_containers():
         for j in range(0, 5):
             assert nvnc[i][j].value == j + 1
 
-    for k, v in nvnc.items():
+    # Note: maps do not have .values()
+    for _, v in nvnc.items():
         for i, j in enumerate(v, start=1):
             assert j.value == i
 
@@ -233,7 +235,7 @@ def test_noncopyable_containers():
             assert nmnc[i][j].value == 10 * j
 
     vsum = 0
-    for k_o, v_o in nmnc.items():
+    for _, v_o in nmnc.items():
         for k_i, v_i in v_o.items():
             assert v_i.value == 10 * k_i
             vsum += v_i.value
@@ -247,7 +249,7 @@ def test_noncopyable_containers():
             assert numnc[i][j].value == 10 * j
 
     vsum = 0
-    for k_o, v_o in numnc.items():
+    for _, v_o in numnc.items():
         for k_i, v_i in v_o.items():
             assert v_i.value == 10 * k_i
             vsum += v_i.value
diff --git a/tests/test_tagbased_polymorphic.py b/tests/test_tagbased_polymorphic.py
index 2574d7de77..94f374da90 100644
--- a/tests/test_tagbased_polymorphic.py
+++ b/tests/test_tagbased_polymorphic.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from pybind11_tests import tagbased_polymorphic as m
 
 
diff --git a/tests/test_union.py b/tests/test_union.py
index e1866e701d..2a2c12fb48 100644
--- a/tests/test_union.py
+++ b/tests/test_union.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from pybind11_tests import union_ as m
 
 
diff --git a/tests/test_virtual_functions.py b/tests/test_virtual_functions.py
index 5ce9abd355..0f2d85fce9 100644
--- a/tests/test_virtual_functions.py
+++ b/tests/test_virtual_functions.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 import pytest
 
 from pybind11_tests import virtual_functions as m
diff --git a/tools/FindEigen3.cmake b/tools/FindEigen3.cmake
index 9c546a05d8..66ffe8e1e5 100644
--- a/tools/FindEigen3.cmake
+++ b/tools/FindEigen3.cmake
@@ -78,4 +78,3 @@ else (EIGEN3_INCLUDE_DIR)
   mark_as_advanced(EIGEN3_INCLUDE_DIR)
 
 endif(EIGEN3_INCLUDE_DIR)
-
diff --git a/tools/libsize.py b/tools/libsize.py
index 5dcb8b0d02..50f88bdb3d 100644
--- a/tools/libsize.py
+++ b/tools/libsize.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from __future__ import print_function, division
 import os
 import sys
@@ -35,4 +36,3 @@
 
 with open(save, 'w') as sf:
     sf.write(str(libsize))
-
diff --git a/tools/mkdoc.py b/tools/mkdoc.py
index cd982e0701..a22aacdefd 100755
--- a/tools/mkdoc.py
+++ b/tools/mkdoc.py
@@ -1,4 +1,5 @@
 #!/usr/bin/env python3
+# -*- coding: utf-8 -*-
 #
 #  Syntax: mkdoc.py [-I<path> ..] [.. a list of header files ..]
 #

From c4fd1fd9872b731e9df21347a09d094489776801 Mon Sep 17 00:00:00 2001
From: Liam Keegan <liam@keegan.ch>
Date: Tue, 21 Jul 2020 19:17:22 +0200
Subject: [PATCH 25/73] CMake improvement: support windows python on msys
 (#2312)

- look for windows python lib when using mingw & msys
  - if not found, then look for system python lib as before
---
 tools/FindPythonLibsNew.cmake | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index d0c8fa2603..994bb1e03b 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -147,7 +147,7 @@ string(REGEX REPLACE "\\\\" "/" PYTHON_PREFIX "${PYTHON_PREFIX}")
 string(REGEX REPLACE "\\\\" "/" PYTHON_INCLUDE_DIR "${PYTHON_INCLUDE_DIR}")
 string(REGEX REPLACE "\\\\" "/" PYTHON_SITE_PACKAGES "${PYTHON_SITE_PACKAGES}")
 
-if(CMAKE_HOST_WIN32 AND NOT (MINGW AND DEFINED ENV{MSYSTEM}))
+if(CMAKE_HOST_WIN32)
     set(PYTHON_LIBRARY
         "${PYTHON_PREFIX}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
 
@@ -159,6 +159,20 @@ if(CMAKE_HOST_WIN32 AND NOT (MINGW AND DEFINED ENV{MSYSTEM}))
             "${_PYTHON_ROOT}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
     endif()
 
+    # if we are in MSYS & MINGW, and we didn't find windows python lib, look for system python lib
+    if(DEFINED ENV{MSYSTEM} AND MINGW AND NOT EXISTS "${PYTHON_LIBRARY}")
+        if(PYTHON_MULTIARCH)
+            set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}/${PYTHON_MULTIARCH}" "${PYTHON_LIBDIR}")
+        else()
+            set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}")
+        endif()
+        unset(PYTHON_LIBRARY)
+        find_library(PYTHON_LIBRARY
+            NAMES "python${PYTHON_LIBRARY_SUFFIX}"
+            PATHS ${_PYTHON_LIBS_SEARCH}
+            NO_DEFAULT_PATH)
+    endif()
+
     # raise an error if the python libs are still not found.
     if(NOT EXISTS "${PYTHON_LIBRARY}")
         message(FATAL_ERROR "Python libraries not found")

From 96c67636132dc25f87ca59e40cb4d40a965fc137 Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 22 Jul 2020 12:05:16 -0700
Subject: [PATCH 26/73] test_builtin_casters.py test_string_view: Python 2
 c++17, c++2a compatibility. (#2314)

Tested with 2.7.18rc1, built with Py_UNICODE_SIZE 4.
Change also tested with Python 3.8.
---
 tests/test_builtin_casters.py | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index 9a49ffab54..a13acd5b97 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -132,24 +132,24 @@ def test_string_view(capture):
     """Tests support for C++17 string_view arguments and return values"""
     assert m.string_view_chars("Hi") == [72, 105]
     assert m.string_view_chars("Hi 🎂") == [72, 105, 32, 0xf0, 0x9f, 0x8e, 0x82]
-    assert m.string_view16_chars("Hi 🎂") == [72, 105, 32, 0xd83c, 0xdf82]
-    assert m.string_view32_chars("Hi 🎂") == [72, 105, 32, 127874]
+    assert m.string_view16_chars(u"Hi 🎂") == [72, 105, 32, 0xd83c, 0xdf82]
+    assert m.string_view32_chars(u"Hi 🎂") == [72, 105, 32, 127874]
     if hasattr(m, "has_u8string"):
         assert m.string_view8_chars("Hi") == [72, 105]
-        assert m.string_view8_chars("Hi 🎂") == [72, 105, 32, 0xf0, 0x9f, 0x8e, 0x82]
+        assert m.string_view8_chars(u"Hi 🎂") == [72, 105, 32, 0xf0, 0x9f, 0x8e, 0x82]
 
-    assert m.string_view_return() == "utf8 secret 🎂"
-    assert m.string_view16_return() == "utf16 secret 🎂"
-    assert m.string_view32_return() == "utf32 secret 🎂"
+    assert m.string_view_return() == u"utf8 secret 🎂"
+    assert m.string_view16_return() == u"utf16 secret 🎂"
+    assert m.string_view32_return() == u"utf32 secret 🎂"
     if hasattr(m, "has_u8string"):
-        assert m.string_view8_return() == "utf8 secret 🎂"
+        assert m.string_view8_return() == u"utf8 secret 🎂"
 
     with capture:
         m.string_view_print("Hi")
         m.string_view_print("utf8 🎂")
-        m.string_view16_print("utf16 🎂")
-        m.string_view32_print("utf32 🎂")
-    assert capture == """
+        m.string_view16_print(u"utf16 🎂")
+        m.string_view32_print(u"utf32 🎂")
+    assert capture == u"""
         Hi 2
         utf8 🎂 9
         utf16 🎂 8
@@ -158,8 +158,8 @@ def test_string_view(capture):
     if hasattr(m, "has_u8string"):
         with capture:
             m.string_view8_print("Hi")
-            m.string_view8_print("utf8 🎂")
-        assert capture == """
+            m.string_view8_print(u"utf8 🎂")
+        assert capture == u"""
             Hi 2
             utf8 🎂 9
         """
@@ -167,9 +167,9 @@ def test_string_view(capture):
     with capture:
         m.string_view_print("Hi, ascii")
         m.string_view_print("Hi, utf8 🎂")
-        m.string_view16_print("Hi, utf16 🎂")
-        m.string_view32_print("Hi, utf32 🎂")
-    assert capture == """
+        m.string_view16_print(u"Hi, utf16 🎂")
+        m.string_view32_print(u"Hi, utf32 🎂")
+    assert capture == u"""
         Hi, ascii 9
         Hi, utf8 🎂 13
         Hi, utf16 🎂 12
@@ -178,8 +178,8 @@ def test_string_view(capture):
     if hasattr(m, "has_u8string"):
         with capture:
             m.string_view8_print("Hi, ascii")
-            m.string_view8_print("Hi, utf8 🎂")
-        assert capture == """
+            m.string_view8_print(u"Hi, utf8 🎂")
+        assert capture == u"""
             Hi, ascii 9
             Hi, utf8 🎂 13
         """

From 441e77704043f1f0944043b56e39d95342e76ac1 Mon Sep 17 00:00:00 2001
From: Boris Staletic <boris.staletic@gmail.com>
Date: Thu, 23 Jul 2020 16:03:55 +0200
Subject: [PATCH 27/73] Use new style __init__ in numpy docs (#2316)

---
 docs/advanced/pycpp/numpy.rst | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/advanced/pycpp/numpy.rst b/docs/advanced/pycpp/numpy.rst
index aef7abe3d7..f1941392fa 100644
--- a/docs/advanced/pycpp/numpy.rst
+++ b/docs/advanced/pycpp/numpy.rst
@@ -81,7 +81,7 @@ buffer objects (e.g. a NumPy matrix).
     constexpr bool rowMajor = Matrix::Flags & Eigen::RowMajorBit;
 
     py::class_<Matrix>(m, "Matrix", py::buffer_protocol())
-        .def("__init__", [](Matrix &m, py::buffer b) {
+        .def("__init__", [](py::buffer b) {
             typedef Eigen::Stride<Eigen::Dynamic, Eigen::Dynamic> Strides;
 
             /* Request a buffer descriptor from Python */
@@ -101,7 +101,7 @@ buffer objects (e.g. a NumPy matrix).
             auto map = Eigen::Map<Matrix, 0, Strides>(
                 static_cast<Scalar *>(info.ptr), info.shape[0], info.shape[1], strides);
 
-            new (&m) Matrix(map);
+            return Matrix(m);
         });
 
 For reference, the ``def_buffer()`` call for this Eigen data type should look

From 134a2ec3f7affc808f8ba19ae5734bb8a47b1c30 Mon Sep 17 00:00:00 2001
From: xkszltl <xkszltl@users.noreply.github.com>
Date: Fri, 24 Jul 2020 01:21:09 +0800
Subject: [PATCH 28/73] Add `.git` suffix to URL because only GitHub itself
 works without it. (#2319)

Fix https://github.com/pybind/pybind11/issues/2318
---
 .gitmodules | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.gitmodules b/.gitmodules
index d063a8e89d..4d698f93f8 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,3 +1,3 @@
 [submodule "tools/clang"]
 	path = tools/clang
-	url = ../../wjakob/clang-cindex-python3
+	url = ../../wjakob/clang-cindex-python3.git

From ef057f12b65a48c91def4efe854123618271eb77 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 22 Jul 2020 10:18:41 -0400
Subject: [PATCH 29/73] test: support pypy2 7.3

---
 tests/test_kwargs_and_defaults.py | 7 +++++++
 tests/test_pytypes.py             | 3 ++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/tests/test_kwargs_and_defaults.py b/tests/test_kwargs_and_defaults.py
index 6c72a93689..531a9fdae7 100644
--- a/tests/test_kwargs_and_defaults.py
+++ b/tests/test_kwargs_and_defaults.py
@@ -2,6 +2,11 @@
 import pytest
 from pybind11_tests import kwargs_and_defaults as m
 
+import platform
+import sys
+
+pypy = platform.python_implementation() == "PyPy"
+
 
 def test_function_signatures(doc):
     assert doc(m.kw_func0) == "kw_func0(arg0: int, arg1: int) -> str"
@@ -146,6 +151,8 @@ def test_keyword_only_args(msg):
     """
 
 
+@pytest.mark.xfail(pypy and sys.version_info < (3, 0),
+                   reason="PyPy2 doesn't seem to double count")
 def test_args_refcount():
     """Issue/PR #1216 - py::args elements get double-inc_ref()ed when combined with regular
     arguments"""
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 5d2ccf8fd1..4cfc707a32 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -322,7 +322,8 @@ def test_memoryview_from_buffer_empty_shape():
     assert view.format == 'B'
     if sys.version_info.major < 3:
         # Python 2 behavior is weird, but Python 3 (the future) is fine.
-        assert bytes(view).startswith(b'<memory at ')
+        # PyPy3 has <memoryview, while CPython 2 has <memory
+        assert bytes(view).startswith(b'<memory')
     else:
         assert bytes(view) == b''
 

From 3d20b73e87a33537318ae96ad607243b1b38ea97 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 22 Jul 2020 10:19:28 -0400
Subject: [PATCH 30/73] test: pass through C++ std for cmake test

---
 tests/test_cmake_build/CMakeLists.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/test_cmake_build/CMakeLists.txt b/tests/test_cmake_build/CMakeLists.txt
index c9b5fcb2e7..cf9a9ca9ff 100644
--- a/tests/test_cmake_build/CMakeLists.txt
+++ b/tests/test_cmake_build/CMakeLists.txt
@@ -13,6 +13,7 @@ function(pybind11_add_build_test name)
   set(build_options "-DCMAKE_PREFIX_PATH=${PROJECT_BINARY_DIR}/mock_install"
                     "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
                     "-DPYTHON_EXECUTABLE:FILEPATH=${PYTHON_EXECUTABLE}"
+                    "-DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}"
                     "-DPYBIND11_CPP_STANDARD=${PYBIND11_CPP_STANDARD}")
   if(NOT ARG_INSTALL)
     list(APPEND build_options "-DPYBIND11_PROJECT_DIR=${PROJECT_SOURCE_DIR}")

From 49007b7ff344ed147a14930f9973a967338811dc Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 22 Jul 2020 10:20:42 -0400
Subject: [PATCH 31/73] test: fix warning/error on Python 2 in 14/17 mode

---
 tests/CMakeLists.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index e4aba75674..d36362ebbd 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -151,6 +151,14 @@ function(pybind11_enable_warnings target_name)
       target_compile_options(${target_name} PRIVATE -Werror)
     endif()
   endif()
+
+  if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
+    if(CMAKE_CXX_STANDARD STREQUAL "14")
+      target_compile_options(${target_name} PUBLIC -Wno-deprecated-register)
+    elseif(NOT CMAKE_CXX_STANDARD VERSION_LESS 17)
+      target_compile_options(${target_name} PUBLIC -Wno-register)
+    endif()
+  endif()
 endfunction()
 
 set(test_targets pybind11_tests)

From a59c6de821a9131612434914954bf3efca2d467f Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 22 Jul 2020 10:23:16 -0400
Subject: [PATCH 32/73] test: allow MSVC/Xcode to run the embed test

---
 tests/CMakeLists.txt            |  4 ++--
 tests/test_embed/CMakeLists.txt | 16 ++++++++++------
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d36362ebbd..b1c72b76ac 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -211,10 +211,10 @@ foreach(target ${test_targets})
 
   # Always write the output file directly into the 'tests' directory (even on MSVC)
   if(NOT CMAKE_LIBRARY_OUTPUT_DIRECTORY)
-    set_target_properties(${target} PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${testdir})
+    set_target_properties(${target} PROPERTIES LIBRARY_OUTPUT_DIRECTORY "${testdir}")
     foreach(config ${CMAKE_CONFIGURATION_TYPES})
       string(TOUPPER ${config} config)
-      set_target_properties(${target} PROPERTIES LIBRARY_OUTPUT_DIRECTORY_${config} ${testdir})
+      set_target_properties(${target} PROPERTIES LIBRARY_OUTPUT_DIRECTORY_${config} "${testdir}")
     endforeach()
   endif()
 endforeach()
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index 8b4f1f843e..c5aa7c6c5e 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -17,25 +17,29 @@ add_executable(test_embed
   catch.cpp
   test_interpreter.cpp
 )
-target_include_directories(test_embed PRIVATE ${CATCH_INCLUDE_DIR})
+target_include_directories(test_embed PRIVATE "${CATCH_INCLUDE_DIR}")
 pybind11_enable_warnings(test_embed)
 
 if(NOT CMAKE_VERSION VERSION_LESS 3.0)
   target_link_libraries(test_embed PRIVATE pybind11::embed)
 else()
-  target_include_directories(test_embed PRIVATE ${PYBIND11_INCLUDE_DIR} ${PYTHON_INCLUDE_DIRS})
-  target_compile_options(test_embed PRIVATE ${PYBIND11_CPP_STANDARD})
-  target_link_libraries(test_embed PRIVATE ${PYTHON_LIBRARIES})
+  target_include_directories(test_embed PRIVATE "${PYBIND11_INCLUDE_DIR}" "${PYTHON_INCLUDE_DIRS}")
+  target_compile_options(test_embed PRIVATE "${PYBIND11_CPP_STANDARD}")
+  target_link_libraries(test_embed PRIVATE "${PYTHON_LIBRARIES}")
 endif()
 
 find_package(Threads REQUIRED)
 target_link_libraries(test_embed PUBLIC ${CMAKE_THREAD_LIBS_INIT})
 
 add_custom_target(cpptest COMMAND $<TARGET_FILE:test_embed>
-                  WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+                  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
 
 pybind11_add_module(external_module THIN_LTO external_module.cpp)
-set_target_properties(external_module PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+set_target_properties(external_module PROPERTIES LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
+foreach(config ${CMAKE_CONFIGURATION_TYPES})
+  string(TOUPPER ${config} config)
+  set_target_properties(external_module PROPERTIES LIBRARY_OUTPUT_DIRECTORY_${config} "${CMAKE_CURRENT_SOURCE_DIR}")
+endforeach()
 add_dependencies(cpptest external_module)
 
 add_dependencies(check cpptest)

From 73dc9786832bcaf0ab5f8284929cb67e211fe04f Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 22 Jul 2020 10:23:48 -0400
Subject: [PATCH 33/73] style: avoid adding virtual environment directories

---
 .gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.gitignore b/.gitignore
index 244bbcaa7a..4dca42ab7e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -37,3 +37,4 @@ MANIFEST
 sosize-*.txt
 pybind11Config*.cmake
 pybind11Targets.cmake
+/*env*

From b16347e51d054789df43d8c66da126d5287d5521 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 22 Jul 2020 10:24:11 -0400
Subject: [PATCH 34/73] ci: enable GHA testing

Adds requirements file too.
---
 .github/workflows/ci.yml | 81 ++++++++++++++++++++++++++++++++++++++++
 tests/requirements.txt   |  3 ++
 2 files changed, 84 insertions(+)
 create mode 100644 .github/workflows/ci.yml
 create mode 100644 tests/requirements.txt

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000000..a2627c7972
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,81 @@
+name: CI
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+      - master
+      - stable
+      - v*
+
+jobs:
+  standard:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu, windows, macos]
+        python:
+        - 2.7
+        - 3.5
+        - 3.8
+        - 3.9-dev
+        - pypy2
+        - pypy3
+
+        include:
+          - os: ubuntu
+            python: 3.6
+          - os: macos
+            python: 3.7
+
+        exclude:
+            # Currently 32bit only, and we build 64bit
+          - os: windows
+            python: pypy2
+          - os: windows
+            python: pypy3
+
+            # Currently can't build due to warning, fixed in CPython > 3.9b5
+          - os: macos
+            python: 3.9-dev
+
+            # Currently broken on embed_test
+          - os: windows
+            python: 3.8
+          - os: windows
+            python: 3.9-dev
+
+    name: Python ${{ matrix.python }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Python ${{ matrix.python }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python }}
+
+    - name: Prepare env
+      run: python -m pip install -r tests/requirements.txt
+
+    - name: Configure
+      shell: bash
+      run: >
+        cmake -S . -B build
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
+
+    - name: Build
+      run: cmake --build build -j 2
+
+    - name: Python tests
+      run: cmake --build build --target pytest -j 2 -v
+
+    - name: C++ tests
+      run: cmake --build build --target cpptest -j 2 -v
+
+    - name: Interface test
+      run: cmake --build build --target test_cmake_build
diff --git a/tests/requirements.txt b/tests/requirements.txt
new file mode 100644
index 0000000000..37e06ca8df
--- /dev/null
+++ b/tests/requirements.txt
@@ -0,0 +1,3 @@
+--extra-index-url https://antocuni.github.io/pypy-wheels/manylinux2010/
+numpy; platform_python_implementation!="PyPy" or sys_platform!="darwin" or python_version<"3.0"
+pytest

From 8b0ccf7657b855e1d4156e39d45b9bb42d433094 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Mon, 20 Jul 2020 15:07:22 -0400
Subject: [PATCH 35/73] style: adding pre-commit check-style.sh

---
 .pre-commit-config.yaml | 11 ++++++++++-
 .travis.yml             |  6 ++----
 CONTRIBUTING.md         |  9 ++++-----
 tools/check-style.sh    | 38 ++++++--------------------------------
 4 files changed, 22 insertions(+), 42 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 63e4c6f7d1..bc478a2b49 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -24,5 +24,14 @@ repos:
   rev: 3.8.2
   hooks:
   - id: flake8
-    additional_dependencies: [flake8-bugbear]
+    additional_dependencies: [flake8-bugbear, pep8-naming]
     exclude: ^(docs/.*|tools/.*)$
+
+- repo: local
+  hooks:
+  - id: check-style
+    name: Classic check-style
+    language: system
+    types:
+    - c++
+    entry: ./tools/check-style.sh
diff --git a/.travis.yml b/.travis.yml
index 12067bca8f..30a9465a28 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,7 +9,7 @@ matrix:
   #   also tests the automatic discovery functions in CMake (Python version, C++ standard).
   - os: linux
     dist: xenial # Necessary to run doxygen 1.8.15
-    name: Style, docs, and pip
+    name: Docs and pip
     cache: false
     before_install:
     - pyenv global $(pyenv whence 2to3)  # activate all python versions
@@ -18,12 +18,10 @@ matrix:
     install:
     # breathe 4.14 doesn't work with bit fields. See https://github.com/michaeljones/breathe/issues/462
     # Latest breathe + Sphinx causes warnings and errors out
-    - $PY_CMD -m pip install --user --upgrade "sphinx<3" sphinx_rtd_theme breathe==4.13.1 flake8 pep8-naming pytest
+    - $PY_CMD -m pip install --user --upgrade "sphinx<3" sphinx_rtd_theme breathe==4.13.1 pytest
     - curl -fsSL https://sourceforge.net/projects/doxygen/files/rel-1.8.15/doxygen-1.8.15.linux.bin.tar.gz/download | tar xz
     - export PATH="$PWD/doxygen-1.8.15/bin:$PATH"
     script:
-    - tools/check-style.sh
-    - flake8
     - $PY_CMD -m sphinx -W -b html docs docs/.build
     - |
       # Make sure setup.py distributes and installs all the headers
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 0997918122..9dd3bd6f6c 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -27,11 +27,10 @@ adhere to the following rules to make the process as smooth as possible:
   do add value by themselves.
 * Add tests for any new functionality and run the test suite (``make pytest``)
   to ensure that no existing features break.
-* Please run [``pre-commit``][pre-commit] and ``tools/check-style.sh`` to check
-  your code matches the project style. (Note that ``check-style.sh`` requires
-  ``gawk``.) Use `pre-commit run --all-files` before committing (or use
-  installed-mode, check pre-commit docs) to verify your code passes before
-  pushing to save time.
+* Please run [``pre-commit``][pre-commit] to check your code matches the
+  project style. (Note that ``gawk`` is required.) Use `pre-commit run
+  --all-files` before committing (or use installed-mode, check pre-commit docs)
+  to verify your code passes before pushing to save time.
 * This project has a strong focus on providing general solutions using a
   minimal amount of code, thus small pull requests are greatly preferred.
 
diff --git a/tools/check-style.sh b/tools/check-style.sh
index 0a9f7d24fc..f7af2a4169 100755
--- a/tools/check-style.sh
+++ b/tools/check-style.sh
@@ -4,45 +4,19 @@
 #
 # This script currently checks for
 #
-# 1. use of tabs instead of spaces
-# 2. MSDOS-style CRLF endings
-# 3. trailing spaces
-# 4. missing space between keyword and parenthesis, e.g.: for(, if(, while(
-# 5. Missing space between right parenthesis and brace, e.g. 'for (...){'
-# 6. opening brace on its own line. It should always be on the same line as the
+# 1. missing space between keyword and parenthesis, e.g.: for(, if(, while(
+# 2. Missing space between right parenthesis and brace, e.g. 'for (...){'
+# 3. opening brace on its own line. It should always be on the same line as the
 #    if/while/for/do statement.
 #
-# Invoke as: tools/check-style.sh
+# Invoke as: tools/check-style.sh <filenames>
 #
 
 check_style_errors=0
 IFS=$'\n'
 
-found="$( GREP_COLORS='mt=41' GREP_COLOR='41' grep $'\t' include tests/*.{cpp,py,h} docs/*.rst -rn --color=always )"
-if [ -n "$found" ]; then
-    # The mt=41 sets a red background for matched tabs:
-    echo -e '\033[31;01mError: found tab characters in the following files:\033[0m'
-    check_style_errors=1
-    echo "$found" | sed -e 's/^/    /'
-fi
-
-
-found="$( grep -IUlr $'\r' include tests/*.{cpp,py,h} docs/*.rst --color=always )"
-if [ -n "$found" ]; then
-    echo -e '\033[31;01mError: found CRLF characters in the following files:\033[0m'
-    check_style_errors=1
-    echo "$found" | sed -e 's/^/    /'
-fi
-
-found="$(GREP_COLORS='mt=41' GREP_COLOR='41' grep '[[:blank:]]\+$' include tests/*.{cpp,py,h} docs/*.rst -rn --color=always )"
-if [ -n "$found" ]; then
-    # The mt=41 sets a red background for matched trailing spaces
-    echo -e '\033[31;01mError: found trailing spaces in the following files:\033[0m'
-    check_style_errors=1
-    echo "$found" | sed -e 's/^/    /'
-fi
 
-found="$(grep '\<\(if\|for\|while\|catch\)(\|){' include tests/*.{cpp,h} -rn --color=always)"
+found="$(grep '\<\(if\|for\|while\|catch\)(\|){' $@ -rn --color=always)"
 if [ -n "$found" ]; then
     echo -e '\033[31;01mError: found the following coding style problems:\033[0m'
     check_style_errors=1
@@ -60,7 +34,7 @@ last && /^\s*{/ {
     last=""
 }
 { last = /(if|for|while|catch|switch)\s*\(.*\)\s*$/ ? $0 : "" }
-' $(find include -type f) tests/*.{cpp,h} docs/*.rst)"
+' $(find include -type f) $@)"
 if [ -n "$found" ]; then
     check_style_errors=1
     echo -e '\033[31;01mError: braces should occur on the same line as the if/while/.. statement. Found issues in the following files:\033[0m'

From 5c936d4b22cbe5ed46208c790c635baf03aed4b1 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 21 Jul 2020 09:34:20 -0400
Subject: [PATCH 36/73] refactor: issue fixed upstream

---
 .pre-commit-config.yaml | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index bc478a2b49..3e68d34f07 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -15,13 +15,12 @@ repos:
   - id: fix-encoding-pragma
 
 - repo: https://github.com/Lucas-C/pre-commit-hooks
-  rev: v1.1.7
+  rev: v1.1.9
   hooks:
   - id: remove-tabs
-    exclude: (Makefile|debian/rules|.gitmodules)(\.in)?$
 
 - repo: https://gitlab.com/pycqa/flake8
-  rev: 3.8.2
+  rev: 3.8.3
   hooks:
   - id: flake8
     additional_dependencies: [flake8-bugbear, pep8-naming]

From 6f3e5e38c90c69f5758365fb1c3b31c8c5a557bc Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 23 Jul 2020 17:21:55 -0400
Subject: [PATCH 37/73] ci: keep travis from running twice

---
 .travis.yml | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/.travis.yml b/.travis.yml
index 30a9465a28..91f9c9decb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,4 +1,11 @@
 language: cpp
+
+branches:
+  only:
+  - master
+  - stable
+  - /^v\d/
+
 matrix:
   include:
   # This config does a few things:
@@ -33,6 +40,7 @@ matrix:
       # Barebones build
       cmake -DCMAKE_BUILD_TYPE=Debug -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DPYTHON_EXECUTABLE=$(which $PY_CMD) .
       make pytest -j 2 && make cpptest -j 2
+
   # The following are regular test configurations, including optional dependencies.
   # With regard to each other they differ in Python version, C++ standard and compiler.
   - os: linux

From 2819ce64a4fcc406822382b9ad70bbe12aec90bf Mon Sep 17 00:00:00 2001
From: Boris Staletic <boris.staletic@gmail.com>
Date: Fri, 24 Jul 2020 18:43:59 +0200
Subject: [PATCH 38/73] Avoid attr("__repr__") in initialize_generic (#2317)

If the default argument value is a class, and not an instance of a
class, `a.value.attr("__repr__")` raises a `ValueError`. Switching to
`repr(a.value)` makes this use case work.

Fixes #2028
---
 include/pybind11/pybind11.h        | 2 +-
 tests/test_kwargs_and_defaults.cpp | 5 +++++
 tests/test_kwargs_and_defaults.py  | 2 ++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index ee28705245..1a415a405f 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -228,7 +228,7 @@ class cpp_function : public function {
             if (a.descr)
                 a.descr = strdup(a.descr);
             else if (a.value)
-                a.descr = strdup(a.value.attr("__repr__")().cast<std::string>().c_str());
+                a.descr = strdup(repr(a.value).cast<std::string>().c_str());
         }
 
         rec->is_constructor = !strcmp(rec->name, "__init__") || !strcmp(rec->name, "__setstate__");
diff --git a/tests/test_kwargs_and_defaults.cpp b/tests/test_kwargs_and_defaults.cpp
index 8f095fe4a6..64bc2377b2 100644
--- a/tests/test_kwargs_and_defaults.cpp
+++ b/tests/test_kwargs_and_defaults.cpp
@@ -123,4 +123,9 @@ TEST_SUBMODULE(kwargs_and_defaults, m) {
     py::class_<KWClass>(m, "KWClass")
         .def("foo0", &KWClass::foo)
         .def("foo1", &KWClass::foo, "x"_a, "y"_a);
+
+    // Make sure a class (not an instance) can be used as a default argument.
+    // The return value doesn't matter, only that the module is importable.
+    m.def("class_default_argument", [](py::object a) { return py::repr(a); },
+        "a"_a = py::module::import("decimal").attr("Decimal"));
 }
diff --git a/tests/test_kwargs_and_defaults.py b/tests/test_kwargs_and_defaults.py
index 531a9fdae7..dad40dbebf 100644
--- a/tests/test_kwargs_and_defaults.py
+++ b/tests/test_kwargs_and_defaults.py
@@ -191,3 +191,5 @@ def test_args_refcount():
     # tuple without having to inc_ref the individual elements, but here we can't, hence the extra
     # refs.
     assert m.mixed_args_refcount(myval, myval, myval) == (exp3 + 3, exp3 + 3, exp3 + 3)
+
+    assert m.class_default_argument() == "<class 'decimal.Decimal'>"

From 7e0a4fb7d0c548231b2dc104054170cb6bebea96 Mon Sep 17 00:00:00 2001
From: tuxmaster5000 <837503+tuxmaster5000@users.noreply.github.com>
Date: Fri, 24 Jul 2020 19:00:48 +0200
Subject: [PATCH 39/73] Fix for #2168 (#2299)

---
 tools/FindCatch.cmake | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/FindCatch.cmake b/tools/FindCatch.cmake
index 9d490c5aad..ad4a4a5938 100644
--- a/tools/FindCatch.cmake
+++ b/tools/FindCatch.cmake
@@ -38,7 +38,7 @@ function(_download_catch version destination_dir)
 endfunction()
 
 # Look for catch locally
-find_path(CATCH_INCLUDE_DIR NAMES catch.hpp PATH_SUFFIXES catch)
+find_path(CATCH_INCLUDE_DIR NAMES catch.hpp PATH_SUFFIXES catch2)
 if(CATCH_INCLUDE_DIR)
   _get_catch_version()
 endif()

From 6a80171c42cbb13ffaefeb3f6a7ff53be0856e86 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 23 Jul 2020 20:30:47 -0400
Subject: [PATCH 40/73] ci: Add clang builds & C++17

---
 .github/workflows/ci.yml | 74 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 71 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a2627c7972..75cff40b6d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -60,22 +60,90 @@ jobs:
     - name: Prepare env
       run: python -m pip install -r tests/requirements.txt
 
-    - name: Configure
+    - name: Configure C++11
       shell: bash
       run: >
+        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
+        -DCMAKE_CXX_STANDARD=11
+        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
+
+    - name: Build C++11
+      run: cmake --build build -j 2
+
+    - name: Python tests C++11
+      run: cmake --build build --target pytest -j 2 -v
+
+    - name: C++11 tests
+      run: cmake --build build --target cpptest -j 2 -v
+
+    - name: Interface test C++11
+      run: cmake --build build --target test_cmake_build
+
+    - name: Configure C++17
+      shell: bash
+      run: >
+        cmake -S . -B build17
+        -DPYBIND17_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DCMAKE_CXX_STANDARD=17
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
 
+    - name: Build C++17
+      run: cmake --build build17 -j 2
+
+    - name: Python tests C++17
+      run: cmake --build build17 --target pytest
+
+    - name: C++17 tests
+      run: cmake --build build17 --target cpptest
+
+    - name: Interface test C++17
+      run: cmake --build build17 --target test_cmake_build
+
+  clang:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        clang:
+          - 3.6
+          - 3.7
+          - 3.8
+          - 3.9
+          - 5
+          - 7
+          - 9
+          - dev
+
+    name: Clang ${{ matrix.clang }}
+    container: "silkeh/clang:${{ matrix.clang }}"
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Add wget and python3
+      run: apt-get update && apt-get install -y python3-dev python3-numpy python3-pytest
+
+    - name: Configure
+      shell: bash
+      run: >
+        cmake --version &&
+        cmake -S . -B build
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+
     - name: Build
       run: cmake --build build -j 2
 
     - name: Python tests
-      run: cmake --build build --target pytest -j 2 -v
+      run: cmake --build build --target pytest
 
     - name: C++ tests
-      run: cmake --build build --target cpptest -j 2 -v
+      run: cmake --build build --target cpptest
 
     - name: Interface test
       run: cmake --build build --target test_cmake_build

From e428a7f6b89625eb153f5346fe85a656803b92a2 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 23 Jul 2020 21:16:54 -0400
Subject: [PATCH 41/73] ci: fix clang warnings

---
 include/pybind11/pytypes.h            |  2 +-
 tests/test_call_policies.cpp          |  1 +
 tests/test_class.cpp                  | 10 +++++++++-
 tests/test_gil_scoped.cpp             |  4 +++-
 tests/test_methods_and_attributes.cpp |  1 +
 tests/test_smart_ptr.cpp              |  2 ++
 tests/test_virtual_functions.cpp      | 21 ++++++++++++++++++++-
 7 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 5152f6804a..536835f7da 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -370,7 +370,7 @@ bool isinstance(handle obj) { return T::check_(obj); }
 template <typename T, detail::enable_if_t<!std::is_base_of<object, T>::value, int> = 0>
 bool isinstance(handle obj) { return detail::isinstance_generic(obj, typeid(T)); }
 
-template <> inline bool isinstance<handle>(handle obj) = delete;
+template <> inline bool isinstance<handle>(handle) = delete;
 template <> inline bool isinstance<object>(handle obj) { return obj.ptr() != nullptr; }
 
 /// \ingroup python_builtins
diff --git a/tests/test_call_policies.cpp b/tests/test_call_policies.cpp
index fd24557834..26c83f81b0 100644
--- a/tests/test_call_policies.cpp
+++ b/tests/test_call_policies.cpp
@@ -46,6 +46,7 @@ TEST_SUBMODULE(call_policies, m) {
     class Parent {
     public:
         Parent() { py::print("Allocating parent."); }
+        Parent(const Parent& parent) = default;
         ~Parent() { py::print("Releasing parent."); }
         void addChild(Child *) { }
         Child *returnChild() { return new Child(); }
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 128bc39e9e..7edcdce363 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -227,6 +227,8 @@ TEST_SUBMODULE(class_, m) {
         static void *operator new(size_t s, void *ptr) { py::print("C placement-new", s); return ptr; }
         static void operator delete(void *p, size_t s) { py::print("C delete", s); return ::operator delete(p); }
         virtual ~AliasedHasOpNewDelSize() = default;
+        AliasedHasOpNewDelSize() = default;
+        AliasedHasOpNewDelSize(const AliasedHasOpNewDelSize&) = delete;
     };
     struct PyAliasedHasOpNewDelSize : AliasedHasOpNewDelSize {
         PyAliasedHasOpNewDelSize() = default;
@@ -277,6 +279,8 @@ TEST_SUBMODULE(class_, m) {
     class ProtectedB {
     public:
         virtual ~ProtectedB() = default;
+        ProtectedB() = default;
+        ProtectedB(const ProtectedB &) = delete;
 
     protected:
         virtual int foo() const { return value; }
@@ -377,7 +381,11 @@ TEST_SUBMODULE(class_, m) {
     py::class_<IsNonFinalFinal>(m, "IsNonFinalFinal", py::is_final());
 }
 
-template <int N> class BreaksBase { public: virtual ~BreaksBase() = default; };
+template <int N> class BreaksBase { public:
+    virtual ~BreaksBase() = default;
+    BreaksBase() = default;
+    BreaksBase(const BreaksBase&) = delete;
+};
 template <int N> class BreaksTramp : public BreaksBase<N> {};
 // These should all compile just fine:
 typedef py::class_<BreaksBase<1>, std::unique_ptr<BreaksBase<1>>, BreaksTramp<1>> DoesntBreak1;
diff --git a/tests/test_gil_scoped.cpp b/tests/test_gil_scoped.cpp
index 76c17fdc78..dc9b7ed224 100644
--- a/tests/test_gil_scoped.cpp
+++ b/tests/test_gil_scoped.cpp
@@ -13,7 +13,9 @@
 
 class VirtClass  {
 public:
-    virtual ~VirtClass() {}
+    virtual ~VirtClass() = default;
+    VirtClass() = default;
+    VirtClass(const VirtClass&) = delete;
     virtual void virtual_func() {}
     virtual void pure_virtual_func() = 0;
 };
diff --git a/tests/test_methods_and_attributes.cpp b/tests/test_methods_and_attributes.cpp
index 901f2046c4..11d4e7b350 100644
--- a/tests/test_methods_and_attributes.cpp
+++ b/tests/test_methods_and_attributes.cpp
@@ -289,6 +289,7 @@ TEST_SUBMODULE(methods_and_attributes, m) {
     class DynamicClass {
     public:
         DynamicClass() { print_default_created(this); }
+        DynamicClass(const DynamicClass&) = delete;
         ~DynamicClass() { print_destroyed(this); }
     };
     py::class_<DynamicClass>(m, "DynamicClass", py::dynamic_attr())
diff --git a/tests/test_smart_ptr.cpp b/tests/test_smart_ptr.cpp
index 6f8f3821a5..bea90691d4 100644
--- a/tests/test_smart_ptr.cpp
+++ b/tests/test_smart_ptr.cpp
@@ -339,6 +339,8 @@ TEST_SUBMODULE(smart_ptr, m) {
     // #187: issue involving std::shared_ptr<> return value policy & garbage collection
     struct ElementBase {
         virtual ~ElementBase() { } /* Force creation of virtual table */
+        ElementBase() = default;
+        ElementBase(const ElementBase&) = delete;
     };
     py::class_<ElementBase, std::shared_ptr<ElementBase>>(m, "ElementBase");
 
diff --git a/tests/test_virtual_functions.cpp b/tests/test_virtual_functions.cpp
index ccf018d997..583c1e647e 100644
--- a/tests/test_virtual_functions.cpp
+++ b/tests/test_virtual_functions.cpp
@@ -130,6 +130,8 @@ class Movable {
 class NCVirt {
 public:
     virtual ~NCVirt() { }
+    NCVirt() = default;
+    NCVirt(const NCVirt&) = delete;
     virtual NonCopyable get_noncopyable(int a, int b) { return NonCopyable(a, b); }
     virtual Movable get_movable(int a, int b) = 0;
 
@@ -151,6 +153,8 @@ struct Base {
     /* for some reason MSVC2015 can't compile this if the function is pure virtual */
     virtual std::string dispatch() const { return {}; };
     virtual ~Base() = default;
+    Base() = default;
+    Base(const Base&) = delete;
 };
 
 struct DispatchIssue : Base {
@@ -221,12 +225,15 @@ TEST_SUBMODULE(virtual_functions, m) {
     // don't invoke Python dispatch classes by default when instantiating C++ classes
     // that were not extended on the Python side
     struct A {
+        A() = default;
+        A(const A&) = delete;
         virtual ~A() {}
         virtual void f() { py::print("A.f()"); }
     };
 
     struct PyA : A {
         PyA() { py::print("PyA.PyA()"); }
+        PyA(const PyA&) = delete;
         ~PyA() { py::print("PyA.~PyA()"); }
 
         void f() override {
@@ -246,12 +253,15 @@ TEST_SUBMODULE(virtual_functions, m) {
     // test_alias_delay_initialization2
     // ... unless we explicitly request it, as in this example:
     struct A2 {
+        A2() = default;
+        A2(const A2&) = delete;
         virtual ~A2() {}
         virtual void f() { py::print("A2.f()"); }
     };
 
     struct PyA2 : A2 {
         PyA2() { py::print("PyA2.PyA2()"); }
+        PyA2(const PyA2&) = delete;
         ~PyA2() { py::print("PyA2.~PyA2()"); }
         void f() override {
             py::print("PyA2.f()");
@@ -282,6 +292,8 @@ TEST_SUBMODULE(virtual_functions, m) {
         std::string v;
         A a;
         explicit OverrideTest(const std::string &v) : v{v} {}
+        OverrideTest() = default;
+        OverrideTest(const OverrideTest&) = delete;
         virtual std::string str_value() { return v; }
         virtual std::string &str_ref() { return v; }
         virtual A A_value() { return a; }
@@ -339,6 +351,8 @@ public: \
         return say_something(1) + " " + std::to_string(unlucky_number()); \
     }
 A_METHODS
+    A_Repeat() = default;
+    A_Repeat(const A_Repeat&) = delete;
     virtual ~A_Repeat() = default;
 };
 class B_Repeat : public A_Repeat {
@@ -364,7 +378,12 @@ D_METHODS
 };
 
 // Base classes for templated inheritance trampolines.  Identical to the repeat-everything version:
-class A_Tpl { A_METHODS; virtual ~A_Tpl() = default; };
+class A_Tpl {
+    A_METHODS;
+    A_Tpl() = default;
+    A_Tpl(const A_Tpl&) = delete;
+    virtual ~A_Tpl() = default;
+};
 class B_Tpl : public A_Tpl { B_METHODS };
 class C_Tpl : public B_Tpl { C_METHODS };
 class D_Tpl : public C_Tpl { D_METHODS };

From 1f53c373e44ab80a1a3d9b0dbc6c4e8dd824e9c1 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 23 Jul 2020 22:55:29 -0400
Subject: [PATCH 42/73] fix: C++17 mode on Clang may error

---
 tests/CMakeLists.txt                                   |  6 +++---
 tests/test_cmake_build/installed_embed/CMakeLists.txt  |  9 +++++++++
 tests/test_cmake_build/installed_target/CMakeLists.txt |  8 ++++++++
 .../test_cmake_build/subdirectory_embed/CMakeLists.txt | 10 ++++++++++
 .../subdirectory_target/CMakeLists.txt                 |  8 ++++++++
 tests/test_embed/CMakeLists.txt                        | 10 ++++++++++
 tools/pybind11Tools.cmake                              |  8 ++++++++
 7 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index b1c72b76ac..1c32ececb4 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -152,10 +152,10 @@ function(pybind11_enable_warnings target_name)
     endif()
   endif()
 
-  if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
-    if(CMAKE_CXX_STANDARD STREQUAL "14")
+  if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
+    if(CMAKE_CXX_STANDARD LESS 17)
       target_compile_options(${target_name} PUBLIC -Wno-deprecated-register)
-    elseif(NOT CMAKE_CXX_STANDARD VERSION_LESS 17)
+    else()
       target_compile_options(${target_name} PUBLIC -Wno-register)
     endif()
   endif()
diff --git a/tests/test_cmake_build/installed_embed/CMakeLists.txt b/tests/test_cmake_build/installed_embed/CMakeLists.txt
index f7fc09c219..6ab3efd470 100644
--- a/tests/test_cmake_build/installed_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_embed/CMakeLists.txt
@@ -8,8 +8,17 @@ message(STATUS "Found pybind11 v${pybind11_VERSION}: ${pybind11_INCLUDE_DIRS}")
 add_executable(test_cmake_build ../embed.cpp)
 target_link_libraries(test_cmake_build PRIVATE pybind11::embed)
 
+
 # Do not treat includes from IMPORTED target as SYSTEM (Python headers in pybind11::embed).
 # This may be needed to resolve header conflicts, e.g. between Python release and debug headers.
 set_target_properties(test_cmake_build PROPERTIES NO_SYSTEM_FROM_IMPORTED ON)
 
 add_custom_target(check $<TARGET_FILE:test_cmake_build> ${PROJECT_SOURCE_DIR}/../test.py)
+
+if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
+  if(CMAKE_CXX_STANDARD LESS 17)
+    target_compile_options(test_cmake_build PUBLIC -Wno-deprecated-register)
+  else()
+    target_compile_options(test_cmake_build PUBLIC -Wno-register)
+  endif()
+endif()
diff --git a/tests/test_cmake_build/installed_target/CMakeLists.txt b/tests/test_cmake_build/installed_target/CMakeLists.txt
index cd3ae6f7d8..38520fa9c0 100644
--- a/tests/test_cmake_build/installed_target/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_target/CMakeLists.txt
@@ -20,3 +20,11 @@ set_target_properties(test_cmake_build PROPERTIES NO_SYSTEM_FROM_IMPORTED ON)
 
 add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
                   ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME})
+
+if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
+  if(CMAKE_CXX_STANDARD LESS 17)
+    target_compile_options(test_cmake_build PUBLIC -Wno-deprecated-register)
+  else()
+    target_compile_options(test_cmake_build PUBLIC -Wno-register)
+  endif()
+endif()
diff --git a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
index 88ba60dd52..003e93c22e 100644
--- a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
@@ -23,3 +23,13 @@ install(TARGETS test_embed_lib
         RUNTIME DESTINATION lib)
 install(EXPORT      test_export
         DESTINATION lib/cmake/test_export/test_export-Targets.cmake)
+
+if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
+  if(CMAKE_CXX_STANDARD LESS 17)
+    target_compile_options(test_embed_lib PUBLIC -Wno-deprecated-register)
+    target_compile_options(test_cmake_build PUBLIC -Wno-deprecated-register)
+  else()
+    target_compile_options(test_embed_lib PUBLIC -Wno-register)
+    target_compile_options(test_cmake_build PUBLIC -Wno-register)
+  endif()
+endif()
diff --git a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
index 6b142d62a9..507cb8b99a 100644
--- a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
@@ -13,3 +13,11 @@ set_target_properties(test_cmake_build PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX
 
 add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
                   ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME})
+
+if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
+  if(CMAKE_CXX_STANDARD LESS 17)
+    target_compile_options(test_cmake_build PUBLIC -Wno-deprecated-register)
+  else()
+    target_compile_options(test_cmake_build PUBLIC -Wno-register)
+  endif()
+endif()
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index c5aa7c6c5e..4eef2dff1d 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -43,3 +43,13 @@ endforeach()
 add_dependencies(cpptest external_module)
 
 add_dependencies(check cpptest)
+
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
+  if(CMAKE_CXX_STANDARD LESS 17)
+    target_compile_options(test_embed PUBLIC -Wno-deprecated-register)
+    target_compile_options(external_module PUBLIC -Wno-deprecated-register)
+  else()
+    target_compile_options(test_embed PUBLIC -Wno-register)
+    target_compile_options(external_module PUBLIC -Wno-register)
+  endif()
+endif()
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index a3603abe97..be536e6b6f 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -224,6 +224,14 @@ function(pybind11_add_module target_name)
     endif()
   endif()
 
+  # Python 2 doesn't really support C++17, Clang warns/errors over it
+  if(CMAKE_CXX_STANDARD
+     AND CMAKE_CXX_COMPILER_ID MATCHES "Clang"
+     AND PYTHON_VERSION VERSION_LESS 3.0
+     AND NOT CMAKE_CXX_STANDARD LESS 17)
+       target_compile_options(${target_name} PUBLIC -Wno-register)
+  endif()
+
   if(ARG_NO_EXTRAS)
     return()
   endif()

From 447067179685df99b151ced52998a4f86cbedc73 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 23 Jul 2020 23:05:22 -0400
Subject: [PATCH 43/73] fix: too many braces on clang 3.6

---
 include/pybind11/numpy.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/pybind11/numpy.h b/include/pybind11/numpy.h
index 8c390c5317..5b6cea2b4d 100644
--- a/include/pybind11/numpy.h
+++ b/include/pybind11/numpy.h
@@ -550,7 +550,7 @@ class array : public buffer {
         forcecast = detail::npy_api::NPY_ARRAY_FORCECAST_
     };
 
-    array() : array({{0}}, static_cast<const double *>(nullptr)) {}
+    array() : array(0, static_cast<const double *>(nullptr)) {}
 
     using ShapeContainer = detail::any_container<ssize_t>;
     using StridesContainer = detail::any_container<ssize_t>;

From 5927c5819f8dd4f6f73ee4e529f455c489a1ba45 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Fri, 24 Jul 2020 00:26:49 -0400
Subject: [PATCH 44/73] chore: update Catch

---
 tests/test_embed/CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index 4eef2dff1d..8c1cb5664f 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -4,7 +4,7 @@ if(${PYTHON_MODULE_EXTENSION} MATCHES "pypy")
   return()
 endif()
 
-find_package(Catch 1.9.3)
+find_package(Catch 2.13.0)
 if(CATCH_FOUND)
   message(STATUS "Building interpreter tests using Catch v${CATCH_VERSION}")
 else()

From aab701399a8c9b9a5c9b3826f3b3fa121cbadc13 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Fri, 24 Jul 2020 11:45:22 -0400
Subject: [PATCH 45/73] ci: cache, build wheels on macOS PyPy3

---
 .github/workflows/ci.yml | 13 +++++++++++++
 tests/requirements.txt   |  1 +
 2 files changed, 14 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 75cff40b6d..c16779a1ad 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -57,6 +57,19 @@ jobs:
       with:
         python-version: ${{ matrix.python }}
 
+    - name: Cache wheels
+      if: startsWith(runner.os, 'macOS')
+      uses: actions/cache@v2
+      with:
+        # This path is specific to macOS - we really only need it for PyPy NumPy wheels
+        # See https://github.com/actions/cache/blob/master/examples.md#python---pip
+        # for ways to do this more generally
+        path: ~/Library/Caches/pip
+        # Look to see if there is a cache hit for the corresponding requirements file
+        key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}
+        restore-keys: |
+          ${{ runner.os }}-pip-
+
     - name: Prepare env
       run: python -m pip install -r tests/requirements.txt
 
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 37e06ca8df..9d691c036a 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,3 +1,4 @@
 --extra-index-url https://antocuni.github.io/pypy-wheels/manylinux2010/
 numpy; platform_python_implementation!="PyPy" or sys_platform!="darwin" or python_version<"3.0"
+numpy<1.19; platform_python_implementation=="PyPy" and sys_platform=="darwin" and python_version>="3.0"
 pytest

From 7b067cc387d10dc98bc55e2a830645131bf6bf0f Mon Sep 17 00:00:00 2001
From: Sergei Izmailov <sergei.a.izmailov@gmail.com>
Date: Mon, 27 Jul 2020 02:44:25 +0300
Subject: [PATCH 46/73] Set __hash__ to None for types that defines __eq__, but
 not __hash__ (#2291)

fixes #2191
---
 include/pybind11/pybind11.h         |  9 +++++++-
 tests/test_operator_overloading.cpp | 32 +++++++++++++++++++++++++++++
 tests/test_operator_overloading.py  | 16 +++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 1a415a405f..87f4645e6a 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1047,6 +1047,13 @@ inline void call_operator_delete(void *p, size_t s, size_t a) {
     #endif
 }
 
+inline void add_class_method(object& cls, const char *name_, const cpp_function &cf) {
+    cls.attr(cf.name()) = cf;
+    if (strcmp(name_, "__eq__") == 0 && !cls.attr("__dict__").contains("__hash__")) {
+      cls.attr("__hash__") = none();
+    }
+}
+
 PYBIND11_NAMESPACE_END(detail)
 
 /// Given a pointer to a member function, cast it to its `Derived` version.
@@ -1144,7 +1151,7 @@ class class_ : public detail::generic_type {
     class_ &def(const char *name_, Func&& f, const Extra&... extra) {
         cpp_function cf(method_adaptor<type>(std::forward<Func>(f)), name(name_), is_method(*this),
                         sibling(getattr(*this, name_, none())), extra...);
-        attr(cf.name()) = cf;
+        add_class_method(*this, name_, cf);
         return *this;
     }
 
diff --git a/tests/test_operator_overloading.cpp b/tests/test_operator_overloading.cpp
index 52fcd33836..f3c2eaafa9 100644
--- a/tests/test_operator_overloading.cpp
+++ b/tests/test_operator_overloading.cpp
@@ -187,6 +187,38 @@ TEST_SUBMODULE(operators, m) {
         .def(py::self *= int())
         .def_readwrite("b", &NestC::b);
     m.def("get_NestC", [](const NestC &c) { return c.value; });
+
+
+    // test_overriding_eq_reset_hash
+    // #2191 Overriding __eq__ should set __hash__ to None
+    struct Comparable {
+        int value;
+        bool operator==(const Comparable& rhs) const {return value == rhs.value;}
+    };
+
+    struct Hashable : Comparable {
+        explicit Hashable(int value): Comparable{value}{};
+        size_t hash() const { return static_cast<size_t>(value); }
+    };
+
+    struct Hashable2 : Hashable {
+        using Hashable::Hashable;
+    };
+
+    py::class_<Comparable>(m, "Comparable")
+        .def(py::init<int>())
+        .def(py::self == py::self);
+
+    py::class_<Hashable>(m, "Hashable")
+        .def(py::init<int>())
+        .def(py::self == py::self)
+        .def("__hash__", &Hashable::hash);
+
+    // define __hash__ before __eq__
+    py::class_<Hashable2>(m, "Hashable2")
+        .def("__hash__", &Hashable::hash)
+        .def(py::init<int>())
+        .def(py::self == py::self);
 }
 
 #ifndef _MSC_VER
diff --git a/tests/test_operator_overloading.py b/tests/test_operator_overloading.py
index 6c927228ce..39e3aee271 100644
--- a/tests/test_operator_overloading.py
+++ b/tests/test_operator_overloading.py
@@ -127,3 +127,19 @@ def test_nested():
     assert abase.value == 42
     del abase, b
     pytest.gc_collect()
+
+
+def test_overriding_eq_reset_hash():
+
+    assert m.Comparable(15) is not m.Comparable(15)
+    assert m.Comparable(15) == m.Comparable(15)
+
+    with pytest.raises(TypeError):
+        hash(m.Comparable(15))  # TypeError: unhashable type: 'm.Comparable'
+
+    for hashable in (m.Hashable, m.Hashable2):
+        assert hashable(15) is not hashable(15)
+        assert hashable(15) == hashable(15)
+
+        assert hash(hashable(15)) == 15
+        assert hash(hashable(15)) == hash(hashable(15))

From 78069057b2dd879a19f1e4121ee25337d64d6f82 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 11:43:56 -0400
Subject: [PATCH 47/73] ci: trim down Appveyor

---
 .appveyor.yml | 45 ++++++---------------------------------------
 1 file changed, 6 insertions(+), 39 deletions(-)

diff --git a/.appveyor.yml b/.appveyor.yml
index 8fbb726108..fbcf8a3784 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -1,64 +1,32 @@
 version: 1.0.{build}
 image:
-- Visual Studio 2017
 - Visual Studio 2015
 test: off
 skip_branch_with_pr: true
 build:
   parallel: true
 platform:
-- x64
 - x86
 environment:
   matrix:
   - PYTHON: 36
-    CPP: 14
     CONFIG: Debug
   - PYTHON: 27
-    CPP: 14
     CONFIG: Debug
-  - CONDA: 36
-    CPP: latest
-    CONFIG: Release
-matrix:
-  exclude:
-    - image: Visual Studio 2015
-      platform: x86
-    - image: Visual Studio 2015
-      CPP: latest
-    - image: Visual Studio 2017
-      CPP: latest
-      platform: x86
 install:
 - ps: |
-    if ($env:PLATFORM -eq "x64") { $env:CMAKE_ARCH = "x64" }
-    if ($env:APPVEYOR_JOB_NAME -like "*Visual Studio 2017*") {
-      $env:CMAKE_GENERATOR = "Visual Studio 15 2017"
-      $env:CMAKE_INCLUDE_PATH = "C:\Libraries\boost_1_64_0"
-      $env:CXXFLAGS = "-permissive-"
-    } else {
-      $env:CMAKE_GENERATOR = "Visual Studio 14 2015"
-    }
-    if ($env:PYTHON) {
-      if ($env:PLATFORM -eq "x64") { $env:PYTHON = "$env:PYTHON-x64" }
-      $env:PATH = "C:\Python$env:PYTHON\;C:\Python$env:PYTHON\Scripts\;$env:PATH"
-      python -W ignore -m pip install --upgrade pip wheel
-      python -W ignore -m pip install pytest numpy --no-warn-script-location
-    } elseif ($env:CONDA) {
-      if ($env:CONDA -eq "27") { $env:CONDA = "" }
-      if ($env:PLATFORM -eq "x64") { $env:CONDA = "$env:CONDA-x64" }
-      $env:PATH = "C:\Miniconda$env:CONDA\;C:\Miniconda$env:CONDA\Scripts\;$env:PATH"
-      $env:PYTHONHOME = "C:\Miniconda$env:CONDA"
-      conda --version
-      conda install -y -q pytest numpy scipy
-    }
+    $env:CMAKE_GENERATOR = "Visual Studio 14 2015"
+    if ($env:PLATFORM -eq "x64") { $env:PYTHON = "$env:PYTHON-x64" }
+    $env:PATH = "C:\Python$env:PYTHON\;C:\Python$env:PYTHON\Scripts\;$env:PATH"
+    python -W ignore -m pip install --upgrade pip wheel
+    python -W ignore -m pip install pytest numpy --no-warn-script-location
 - ps: |
     Start-FileDownload 'http://bitbucket.org/eigen/eigen/get/3.3.3.zip'
     7z x 3.3.3.zip -y > $null
     $env:CMAKE_INCLUDE_PATH = "eigen-eigen-67e894c6cd8f;$env:CMAKE_INCLUDE_PATH"
 build_script:
 - cmake -G "%CMAKE_GENERATOR%" -A "%CMAKE_ARCH%"
-    -DPYBIND11_CPP_STANDARD=/std:c++%CPP%
+    -DPYBIND11_CPP_STANDARD=/std:c++14
     -DPYBIND11_WERROR=ON
     -DDOWNLOAD_CATCH=ON
     -DCMAKE_SUPPRESS_REGENERATION=1
@@ -66,5 +34,4 @@ build_script:
 - set MSBuildLogger="C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll"
 - cmake --build . --config %CONFIG% --target pytest -- /m /v:m /logger:%MSBuildLogger%
 - cmake --build . --config %CONFIG% --target cpptest -- /m /v:m /logger:%MSBuildLogger%
-- if "%CPP%"=="latest" (cmake --build . --config %CONFIG% --target test_cmake_build -- /m /v:m /logger:%MSBuildLogger%)
 on_failure: if exist "tests\test_cmake_build" type tests\test_cmake_build\*.log*

From 9521bc56a8810a2d336983b1ef3d0ad2cbd7bae5 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 11:47:53 -0400
Subject: [PATCH 48/73] ci: drop parts from Travis

---
 .travis.yml | 192 +++-------------------------------------------------
 1 file changed, 11 insertions(+), 181 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 91f9c9decb..4893056332 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -41,143 +41,6 @@ matrix:
       cmake -DCMAKE_BUILD_TYPE=Debug -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DPYTHON_EXECUTABLE=$(which $PY_CMD) .
       make pytest -j 2 && make cpptest -j 2
 
-  # The following are regular test configurations, including optional dependencies.
-  # With regard to each other they differ in Python version, C++ standard and compiler.
-  - os: linux
-    dist: trusty
-    name: Python 2.7, c++11, gcc 4.8
-    env: PYTHON=2.7 CPP=11 GCC=4.8
-    addons:
-      apt:
-        packages:
-          - cmake=2.\*
-          - cmake-data=2.\*
-  - os: linux
-    dist: trusty
-    name: Python 3.6, c++11, gcc 4.8
-    env: PYTHON=3.6 CPP=11 GCC=4.8
-    addons:
-      apt:
-        sources:
-          - deadsnakes
-        packages:
-          - python3.6-dev
-          - python3.6-venv
-          - cmake=2.\*
-          - cmake-data=2.\*
-  - os: linux
-    dist: trusty
-    env: PYTHON=2.7 CPP=14 GCC=6 CMAKE=1
-    name: Python 2.7, c++14, gcc 6, CMake test
-    addons:
-      apt:
-        sources:
-          - ubuntu-toolchain-r-test
-        packages:
-          - g++-6
-  - os: linux
-    dist: trusty
-    name: Python 3.5, c++14, gcc 6, Debug build
-    # N.B. `ensurepip` could be installed transitively by `python3.5-venv`, but
-    # seems to have apt conflicts (at least for Trusty). Use Docker instead.
-    services: docker
-    env: DOCKER=debian:stretch PYTHON=3.5 CPP=14 GCC=6 DEBUG=1
-  - os: linux
-    dist: xenial
-    env: PYTHON=3.6 CPP=17 GCC=7
-    name: Python 3.6, c++17, gcc 7
-    addons:
-      apt:
-        sources:
-          - deadsnakes
-          - ubuntu-toolchain-r-test
-        packages:
-          - g++-7
-          - python3.6-dev
-          - python3.6-venv
-  - os: linux
-    dist: xenial
-    env: PYTHON=3.6 CPP=17 CLANG=7
-    name: Python 3.6, c++17, Clang 7
-    addons:
-      apt:
-        sources:
-          - deadsnakes
-          - llvm-toolchain-xenial-7
-        packages:
-          - python3.6-dev
-          - python3.6-venv
-          - clang-7
-          - libclang-7-dev
-          - llvm-7-dev
-          - lld-7
-          - libc++-7-dev
-          - libc++abi-7-dev  # Why is this necessary???
-  - os: linux
-    dist: xenial
-    env: PYTHON=3.8 CPP=17 GCC=7
-    name: Python 3.8, c++17, gcc 7
-    addons:
-      apt:
-        sources:
-          - deadsnakes
-          - ubuntu-toolchain-r-test
-        packages:
-          - g++-7
-          - python3.8-dev
-          - python3.8-venv
-  - os: linux
-    dist: xenial
-    env: PYTHON=3.9 CPP=17 GCC=7
-    name: Python 3.9 beta, c++17, gcc 7 (w/o numpy/scipy) # TODO: update build name when the numpy/scipy wheels become available
-    addons:
-      apt:
-        sources:
-          - deadsnakes
-          - ubuntu-toolchain-r-test
-        packages:
-          - g++-7
-          - python3.9-dev
-          - python3.9-venv
-    # Currently there are no numpy/scipy wheels available for python3.9
-    # TODO: remove next install and script clause when the wheels become available
-    install:
-      - $PY_CMD -m pip install --user --upgrade pytest
-    script:
-      - |
-        # Barebones build
-        cmake -DCMAKE_BUILD_TYPE=Debug -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DPYTHON_EXECUTABLE=$(which $PY_CMD) .
-        make pytest -j 2 && make cpptest -j 2
-  - os: osx
-    name: Python 2.7, c++14, AppleClang 7.3, CMake test
-    osx_image: xcode7.3
-    env: PYTHON=2.7 CPP=14 CLANG CMAKE=1
-  - os: osx
-    name: Python 3.8, c++14, AppleClang 9, Debug build
-    osx_image: xcode9.4
-    env: PYTHON=3.8 CPP=14 CLANG DEBUG=1
-  # Test a PyPy 2.7 build
-  - os: linux
-    dist: trusty
-    env: PYPY=7.3.1 PYTHON=2.7 CPP=11 GCC=4.8
-    name: PyPy 7.3, Python 2.7, c++11, gcc 4.8
-    addons:
-      apt:
-        packages:
-          - libblas-dev
-          - liblapack-dev
-          - gfortran
-  - os: linux
-    dist: xenial
-    env: PYPY=7.3.1 PYTHON=3.6 CPP=11 GCC=5
-    name: PyPy 7.3, Python 3.6, c++11, gcc 5
-    addons:
-      apt:
-        packages:
-          - libblas-dev
-          - liblapack-dev
-          - gfortran
-          - g++-5
   # Build in 32-bit mode and tests against the CMake-installed version
   - os: linux
     dist: trusty
@@ -197,32 +60,19 @@ matrix:
           cmake ../pybind11-tests ${CMAKE_EXTRA_ARGS} -DPYBIND11_WERROR=ON
           make pytest -j 2"
         set +ex
-  allow_failures:
-    - name: Python 3.9 beta, c++17, gcc 7 (w/o numpy/scipy)
-    - name: PyPy 7.3, Python 2.7, c++11, gcc 4.8
 cache:
   directories:
   - $HOME/.local/bin
   - $HOME/.local/lib
   - $HOME/.local/include
-  - $HOME/Library/Python
 before_install:
 - |
   # Configure build variables
   set -ex
-  if [ "$TRAVIS_OS_NAME" = "linux" ]; then
-    if [ -n "$CLANG" ]; then
-      export CXX=clang++-$CLANG CC=clang-$CLANG
-      EXTRA_PACKAGES+=" clang-$CLANG llvm-$CLANG-dev"
-    else
-      if [ -z "$GCC" ]; then GCC=4.8
-      else EXTRA_PACKAGES+=" g++-$GCC"
-      fi
-      export CXX=g++-$GCC CC=gcc-$GCC
-    fi
-  elif [ "$TRAVIS_OS_NAME" = "osx" ]; then
-    export CXX=clang++ CC=clang;
+  if [ -z "$GCC" ]; then GCC=4.8
+  else EXTRA_PACKAGES+=" g++-$GCC"
   fi
+  export CXX=g++-$GCC CC=gcc-$GCC
   if [ -n "$CPP" ]; then CPP=-std=c++$CPP; fi
   if [ "${PYTHON:0:1}" = "3" ]; then PY=3; fi
   if [ -n "$DEBUG" ]; then CMAKE_EXTRA_ARGS+=" -DCMAKE_BUILD_TYPE=Debug"; fi
@@ -241,18 +91,12 @@ before_install:
     SCRIPT_RUN_PREFIX="docker exec --tty $containerid"
     $SCRIPT_RUN_PREFIX sh -c 'for s in 0 15; do sleep $s; apt-get update && apt-get -qy dist-upgrade && break; done'
   else
-    if [ -n "$PYPY" ]; then
-      curl -fSL https://bitbucket.org/pypy/pypy/downloads/pypy$PYTHON-v$PYPY-linux64.tar.bz2 | tar xj
-      PY_CMD=$(echo `pwd`/pypy$PYTHON-v$PYPY-linux64/bin/pypy$PY)
-      CMAKE_EXTRA_ARGS+=" -DPYTHON_EXECUTABLE:FILEPATH=$PY_CMD"
-    else
-      PY_CMD=python$PYTHON
-      if [ "$TRAVIS_OS_NAME" = "osx" ]; then
-        if [ "$PY" = "3" ]; then
-          brew update && brew unlink python@2 && (brew upgrade python || brew install python)
-        else
-          curl -fsSL https://bootstrap.pypa.io/get-pip.py | $PY_CMD - --user
-        fi
+    PY_CMD=python$PYTHON
+    if [ "$TRAVIS_OS_NAME" = "osx" ]; then
+      if [ "$PY" = "3" ]; then
+        brew update && brew unlink python@2 && (brew upgrade python || brew install python)
+      else
+        curl -fsSL https://bootstrap.pypa.io/get-pip.py | $PY_CMD - --user
       fi
     fi
     if [ "$PY" = 3 ] || [ -n "$PYPY" ]; then
@@ -278,24 +122,10 @@ install:
         libeigen3-dev libboost-dev cmake make ${EXTRA_PACKAGES} && break; done"
   else
 
-    if [ "$CLANG" = "7" ]; then
-      export CXXFLAGS="-stdlib=libc++"
-    fi
-
     export NPY_NUM_BUILD_JOBS=2
     local PIP_CMD=""
-    if [ -n "$PYPY" ]; then
-      # For expediency, install only versions that are available on the extra index.
-      echo "Not installing numpy, scipy as working wheels are not available"
-      # travis_wait 30 $PY_CMD -m pip install --user --upgrade --extra-index-url https://antocuni.github.io/pypy-wheels/manylinux2010 \
-      #    numpy scipy
-      echo "Installing pytest"
-      travis_wait 30 \
-        $PY_CMD -m pip install --user --upgrade pytest
-    else
-      echo "Installing pytest, numpy, scipy..."
-      $PY_CMD -m pip install --user --upgrade pytest numpy scipy
-    fi
+    echo "Installing pytest, numpy, scipy..."
+    $PY_CMD -m pip install --user --upgrade pytest numpy scipy
     echo "done."
 
     mkdir eigen

From 1b880dfd5aee33087b357c49c593c46250b42247 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 13:44:10 -0400
Subject: [PATCH 49/73] ci: download EIGEN

---
 .github/workflows/ci.yml        |  4 ++-
 tests/CMakeLists.txt            | 48 +++++++++++++++++++++++++--------
 tests/test_embed/CMakeLists.txt |  2 +-
 3 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c16779a1ad..627499c393 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -80,6 +80,7 @@ jobs:
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
 
@@ -101,6 +102,7 @@ jobs:
         cmake -S . -B build17
         -DPYBIND17_WERROR=ON
         -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=17
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
 
@@ -138,7 +140,7 @@ jobs:
     - uses: actions/checkout@v2
 
     - name: Add wget and python3
-      run: apt-get update && apt-get install -y python3-dev python3-numpy python3-pytest
+      run: apt-get update && apt-get install -y python3-dev python3-numpy python3-pytest libeigen3-dev
 
     - name: Configure
       shell: bash
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 1c32ececb4..fda6aac8a9 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -97,6 +97,8 @@ set(PYBIND11_CROSS_MODULE_GIL_TESTS
   test_gil_scoped.py
 )
 
+option(DOWNLOAD_EIGEN "Download EIGEN (requires CMake 3.11+)" OFF)
+
 # Check if Eigen is available; if not, remove from PYBIND11_TEST_FILES (but
 # keep it in PYBIND11_PYTEST_FILES, so that we get the "eigen is not installed"
 # skip message).
@@ -105,18 +107,42 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
   # Try loading via newer Eigen's Eigen3Config first (bypassing tools/FindEigen3.cmake).
   # Eigen 3.3.1+ exports a cmake 3.0+ target for handling dependency requirements, but also
   # produces a fatal error if loaded from a pre-3.0 cmake.
-  if (NOT CMAKE_VERSION VERSION_LESS 3.0)
-    find_package(Eigen3 3.2.7 QUIET CONFIG)
-    if (EIGEN3_FOUND)
-      if (EIGEN3_VERSION_STRING AND NOT EIGEN3_VERSION_STRING VERSION_LESS 3.3.1)
-        set(PYBIND11_EIGEN_VIA_TARGET 1)
+  if(DOWNLOAD_EIGEN)
+    if(CMAKE_VERSION VERSION_LESS 3.11)
+      message(FATAL_ERROR "CMake 3.11+ required when using DOWNLOAD_EIGEN")
+    endif()
+
+    set(EIGEN3_VERSION_STRING "3.3.7")
+
+    include(FetchContent)
+    FetchContent_Declare(
+      eigen
+      GIT_REPOSITORY https://gitlab.com/libeigen/eigen.git
+      GIT_TAG ${EIGEN3_VERSION_STRING}
+    )
+
+    FetchContent_GetProperties(eigen)
+    if(NOT eigen_POPULATED)
+      message(STATUS "Downloading Eigen")
+      FetchContent_Populate(eigen)
+    endif()
+
+    set(EIGEN3_INCLUDE_DIR ${eigen_SOURCE_DIR})
+    set(EIGEN3_FOUND TRUE)
+  else()
+    if (NOT CMAKE_VERSION VERSION_LESS 3.0)
+      find_package(Eigen3 3.2.7 QUIET CONFIG)
+      if (EIGEN3_FOUND)
+        if (EIGEN3_VERSION_STRING AND NOT EIGEN3_VERSION_STRING VERSION_LESS 3.3.1)
+          set(PYBIND11_EIGEN_VIA_TARGET TRUE)
+        endif()
       endif()
     endif()
-  endif()
-  if (NOT EIGEN3_FOUND)
-    # Couldn't load via target, so fall back to allowing module mode finding, which will pick up
-    # tools/FindEigen3.cmake
-    find_package(Eigen3 3.2.7 QUIET)
+    if (NOT EIGEN3_FOUND)
+      # Couldn't load via target, so fall back to allowing module mode finding, which will pick up
+      # tools/FindEigen3.cmake
+      find_package(Eigen3 3.2.7 QUIET)
+    endif()
   endif()
 
   if(EIGEN3_FOUND)
@@ -129,7 +155,7 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     message(STATUS "Building tests with Eigen v${EIGEN3_VERSION}")
   else()
     list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
-    message(STATUS "Building tests WITHOUT Eigen")
+    message(STATUS "Building tests WITHOUT Eigen, use -DDOWNLOAD_EIGEN on CMake 3.11+ to download")
   endif()
 endif()
 
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index 8c1cb5664f..1e0ebde745 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -9,7 +9,7 @@ if(CATCH_FOUND)
   message(STATUS "Building interpreter tests using Catch v${CATCH_VERSION}")
 else()
   message(STATUS "Catch not detected. Interpreter tests will be skipped. Install Catch headers"
-                 " manually or use `cmake -DDOWNLOAD_CATCH=1` to fetch them automatically.")
+                 " manually or use `cmake -DDOWNLOAD_CATCH=ON` to fetch them automatically.")
   return()
 endif()
 

From 2ee1bcd9a4b458dab25ad72815fde29ac9054a33 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 13:50:31 -0400
Subject: [PATCH 50/73] ci: add GHA badge

---
 README.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/README.md b/README.md
index 35d2d76ff9..ae7b01bbe0 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,7 @@
 [![Documentation Status](https://readthedocs.org/projects/pybind11/badge/?version=master)](http://pybind11.readthedocs.org/en/master/?badge=master)
 [![Documentation Status](https://readthedocs.org/projects/pybind11/badge/?version=stable)](http://pybind11.readthedocs.org/en/stable/?badge=stable)
 [![Gitter chat](https://img.shields.io/gitter/room/gitterHQ/gitter.svg)](https://gitter.im/pybind/Lobby)
+[![CI](https://github.com/pybind/pybind11/workflows/CI/badge.svg)](https://github.com/pybind/pybind11/actions)
 [![Build Status](https://travis-ci.org/pybind/pybind11.svg?branch=master)](https://travis-ci.org/pybind/pybind11)
 [![Build status](https://ci.appveyor.com/api/projects/status/riaj54pn4h08xy40?svg=true)](https://ci.appveyor.com/project/wjakob/pybind11)
 

From 2fbbd51084dd439e6a456ee5b61733b1eccb2116 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 13:54:11 -0400
Subject: [PATCH 51/73] ci: add gcc

---
 .github/workflows/ci.yml | 96 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 95 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 627499c393..d69ab1cefc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -126,7 +126,6 @@ jobs:
         clang:
           - 3.6
           - 3.7
-          - 3.8
           - 3.9
           - 5
           - 7
@@ -162,3 +161,98 @@ jobs:
 
     - name: Interface test
       run: cmake --build build --target test_cmake_build
+
+  gcc:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        gcc:
+          - 7
+          - latest
+
+    name: 🐍 3 GCC ${{ matrix.gcc }}
+    container: "gcc:${{ matrix.gcc }}"
+
+    steps:
+    - uses: actions/checkout@v1
+
+    - name: Add Python 3
+      run: apt-get update; apt-get install -y python3-dev python3-numpy python3-pytest python3-pip libeigen3-dev
+
+    - name: Update pip
+      run: python3 -m pip install --upgrade pip
+
+    - name: Setup CMake 3.18
+      uses: jwlawson/actions-setup-cmake@v1.3
+      with:
+        cmake-version: 3.18
+
+    - name: Configure
+      shell: bash
+      run: >
+        cmake --version &&
+        cmake -S . -B build
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DCMAKE_CXX_STANDARD=11
+        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+
+    - name: Build
+      run: cmake --build build -j 2
+
+    - name: Python tests
+      run: cmake --build build --target pytest
+
+    - name: C++ tests
+      run: cmake --build build --target cpptest
+
+    - name: Interface test
+      run: cmake --build build --target test_cmake_build
+
+  centos:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        centos:
+          - 7  # GCC 4.8
+          - 8
+
+    name: "🐍 3 • CentOS ${{ matrix.centos }}"
+    container: "centos:${{ matrix.centos }}"
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Add Python 3
+      run: yum update -y && yum install -y python3-devel gcc-c++ make git
+
+    - name: Update pip
+      run: python3 -m pip install --upgrade pip
+
+    - name: Install dependencies
+      run: python3 -m pip install cmake -r tests/requirements.txt
+
+    - name: Configure
+      shell: bash
+      run: >
+        cmake --version &&
+        cmake -S . -B build
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DDOWNLOAD_EIGEN=ON
+        -DCMAKE_CXX_STANDARD=11
+        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+
+    - name: Build
+      run: cmake --build build -j 2
+
+    - name: Python tests
+      run: cmake --build build --target pytest
+
+    - name: C++ tests
+      run: cmake --build build --target cpptest
+
+    - name: Interface test
+      run: cmake --build build --target test_cmake_build

From e450ea05369a5d3f7f12bf536e023c834e1488f7 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 14:15:20 -0400
Subject: [PATCH 52/73] ci: add docker build to GHA

---
 .github/workflows/ci.yml |  35 +++++++++++-
 .travis.yml              | 115 +++++++--------------------------------
 2 files changed, 54 insertions(+), 96 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d69ab1cefc..f12f380ee1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -46,7 +46,7 @@ jobs:
           - os: windows
             python: 3.9-dev
 
-    name: Python ${{ matrix.python }} on ${{ matrix.os }}
+    name: 🐍 ${{ matrix.python }} on ${{ matrix.os }}
     runs-on: ${{ matrix.os }}-latest
 
     steps:
@@ -256,3 +256,36 @@ jobs:
 
     - name: Interface test
       run: cmake --build build --target test_cmake_build
+
+  install-classic:
+    name: "🐍 3.5 32-bit Linux install"
+    runs-on: ubuntu-latest
+    container: i386/debian:stretch
+
+    steps:
+    - uses: actions/checkout@v1
+
+    - name: Install requirements
+      run: |
+        apt-get update
+        apt-get install -y git make cmake g++ libeigen3-dev python3-dev python3-pip python3-pytest
+
+    - name: Configure for install
+      run: cmake -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") -DPYBIND11_INSTALL=1 -DPYBIND11_TEST=0 .
+
+    - name: Make and install
+      run: make install
+
+    - name: Copy tests to new directory
+      run: cp -a tests /pybind11-tests
+
+    - name: Make a new test directory
+      run: mkdir /build-tests
+
+    - name: Configure tests
+      run: cmake -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") ../pybind11-tests -DPYBIND11_WERROR=ON
+      working-directory: /build-tests
+
+    - name: Run tests
+      run: make pytest -j 2
+      working-directory: /build-tests
diff --git a/.travis.yml b/.travis.yml
index 4893056332..f23c29ab41 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -40,26 +40,6 @@ matrix:
       # Barebones build
       cmake -DCMAKE_BUILD_TYPE=Debug -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DPYTHON_EXECUTABLE=$(which $PY_CMD) .
       make pytest -j 2 && make cpptest -j 2
-
-  # Build in 32-bit mode and tests against the CMake-installed version
-  - os: linux
-    dist: trusty
-    services: docker
-    env: DOCKER=i386/debian:stretch PYTHON=3.5 CPP=14 GCC=6 INSTALL=1
-    name: Python 3.5, c++14, gcc 6, 32-bit
-    script:
-      - |
-        # Consolidated 32-bit Docker Build + Install
-        set -ex
-        $SCRIPT_RUN_PREFIX sh -c "
-          set -ex
-          cmake ${CMAKE_EXTRA_ARGS} -DPYBIND11_INSTALL=1 -DPYBIND11_TEST=0 .
-          make install
-          cp -a tests /pybind11-tests
-          mkdir /build-tests && cd /build-tests
-          cmake ../pybind11-tests ${CMAKE_EXTRA_ARGS} -DPYBIND11_WERROR=ON
-          make pytest -j 2"
-        set +ex
 cache:
   directories:
   - $HOME/.local/bin
@@ -80,90 +60,35 @@ before_install:
 - |
   # Initialize environment
   set -ex
-  if [ -n "$DOCKER" ]; then
-    docker pull $DOCKER
-
-    containerid=$(docker run --detach --tty \
-      --volume="$PWD":/pybind11 --workdir=/pybind11 \
-      --env="CC=$CC" --env="CXX=$CXX" --env="DEBIAN_FRONTEND=$DEBIAN_FRONTEND" \
-      --env=GCC_COLORS=\  \
-      $DOCKER)
-    SCRIPT_RUN_PREFIX="docker exec --tty $containerid"
-    $SCRIPT_RUN_PREFIX sh -c 'for s in 0 15; do sleep $s; apt-get update && apt-get -qy dist-upgrade && break; done'
-  else
-    PY_CMD=python$PYTHON
-    if [ "$TRAVIS_OS_NAME" = "osx" ]; then
-      if [ "$PY" = "3" ]; then
-        brew update && brew unlink python@2 && (brew upgrade python || brew install python)
-      else
-        curl -fsSL https://bootstrap.pypa.io/get-pip.py | $PY_CMD - --user
-      fi
-    fi
-    if [ "$PY" = 3 ] || [ -n "$PYPY" ]; then
-      $PY_CMD -m ensurepip --user
+  PY_CMD=python$PYTHON
+  if [ "$TRAVIS_OS_NAME" = "osx" ]; then
+    if [ "$PY" = "3" ]; then
+      brew update && brew unlink python@2 && (brew upgrade python || brew install python)
+    else
+      curl -fsSL https://bootstrap.pypa.io/get-pip.py | $PY_CMD - --user
     fi
-    $PY_CMD --version
-    $PY_CMD -m pip install --user --upgrade pip wheel
   fi
+  if [ "$PY" = 3 ] || [ -n "$PYPY" ]; then
+    $PY_CMD -m ensurepip --user
+  fi
+  $PY_CMD --version
+  $PY_CMD -m pip install --user --upgrade pip wheel
   set +ex
 install:
 - |
   # Install dependencies
   set -ex
   cmake --version
-  if [ -n "$DOCKER" ]; then
-    if [ -n "$DEBUG" ]; then
-      PY_DEBUG="python$PYTHON-dbg python$PY-scipy-dbg"
-      CMAKE_EXTRA_ARGS+=" -DPYTHON_EXECUTABLE=/usr/bin/python${PYTHON}dm"
-    fi
-    $SCRIPT_RUN_PREFIX sh -c "for s in 0 15; do sleep \$s; \
-      apt-get -qy --no-install-recommends install \
-        $PY_DEBUG python$PYTHON-dev python$PY-pytest python$PY-scipy \
-        libeigen3-dev libboost-dev cmake make ${EXTRA_PACKAGES} && break; done"
-  else
 
-    export NPY_NUM_BUILD_JOBS=2
-    local PIP_CMD=""
-    echo "Installing pytest, numpy, scipy..."
-    $PY_CMD -m pip install --user --upgrade pytest numpy scipy
-    echo "done."
+  export NPY_NUM_BUILD_JOBS=2
+  local PIP_CMD=""
+  echo "Installing pytest, numpy, scipy..."
+  $PY_CMD -m pip install --user --upgrade pytest numpy scipy
+  echo "done."
 
-    mkdir eigen
-    curl -fsSL https://bitbucket.org/eigen/eigen/get/3.3.4.tar.bz2 | \
-        tar --extract -j --directory=eigen --strip-components=1
-    export CMAKE_INCLUDE_PATH="${CMAKE_INCLUDE_PATH:+$CMAKE_INCLUDE_PATH:}$PWD/eigen"
-  fi
-  set +ex
-script:
-- |
-  # CMake Configuration
-  set -ex
-  $SCRIPT_RUN_PREFIX cmake ${CMAKE_EXTRA_ARGS} \
-    -DPYBIND11_PYTHON_VERSION=$PYTHON \
-    -DPYBIND11_CPP_STANDARD=$CPP \
-    -DPYBIND11_WERROR=${WERROR:-ON} \
-    -DDOWNLOAD_CATCH=${DOWNLOAD_CATCH:-ON} \
-    .
-  set +ex
-- |
-  # pytest
-  set -ex
-  $SCRIPT_RUN_PREFIX make pytest -j 2 VERBOSE=1
-  set +ex
-- |
-  # cpptest
-  set -ex
-  $SCRIPT_RUN_PREFIX make cpptest -j 2
-  set +ex
-- |
-  # CMake Build Interface
-  set -ex
-  if [ -n "$CMAKE" ]; then $SCRIPT_RUN_PREFIX make test_cmake_build; fi
+  mkdir eigen
+  curl -fsSL https://bitbucket.org/eigen/eigen/get/3.3.4.tar.bz2 | \
+      tar --extract -j --directory=eigen --strip-components=1
+  export CMAKE_INCLUDE_PATH="${CMAKE_INCLUDE_PATH:+$CMAKE_INCLUDE_PATH:}$PWD/eigen"
   set +ex
 after_failure: cat tests/test_cmake_build/*.log*
-after_script:
-- |
-  # Cleanup (Docker)
-  set -ex
-  if [ -n "$DOCKER" ]; then docker stop "$containerid"; docker rm "$containerid"; fi
-  set +ex

From 249a13bd6e6bf105f6034758f38f1d940899b557 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 14:37:39 -0400
Subject: [PATCH 53/73] ci: move docs check to GHA

---
 .github/workflows/ci.yml | 30 +++++++++++++
 .travis.yml              | 94 ----------------------------------------
 README.md                |  1 -
 3 files changed, 30 insertions(+), 95 deletions(-)
 delete mode 100644 .travis.yml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f12f380ee1..5a854b6f9c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -289,3 +289,33 @@ jobs:
     - name: Run tests
       run: make pytest -j 2
       working-directory: /build-tests
+
+
+  doxygen:
+    name: Docs test
+    runs-on: ubuntu-latest
+    container: alpine:3.12
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Install requirements
+      run: apk add doxygen python3-dev
+
+    - name: Ensure pip
+      run: python3 -m ensurepip
+
+    - name: Install python docs requirements
+      run: python3 -m pip install "sphinx<3" sphinx_rtd_theme breathe==4.13.1 pytest setuptools
+
+    - name: Build docs
+      run: python3 -m sphinx -W -b html docs docs/.build
+
+    - name: Make SDist
+      run: python3 setup.py sdist
+
+    - name: Compare Dists (headers only)
+      run: |
+        python3 -m pip install --user -U ./dist/*
+        installed=$(python3 -c "import pybind11; print(pybind11.get_include(True) + '/pybind11')")
+        diff -rq $installed ./include/pybind11
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index f23c29ab41..0000000000
--- a/.travis.yml
+++ /dev/null
@@ -1,94 +0,0 @@
-language: cpp
-
-branches:
-  only:
-  - master
-  - stable
-  - /^v\d/
-
-matrix:
-  include:
-  # This config does a few things:
-  # - Checks C++ and Python code styles (check-style.sh and flake8).
-  # - Makes sure sphinx can build the docs without any errors or warnings.
-  # - Tests setup.py sdist and install (all header files should be present).
-  # - Makes sure that everything still works without optional deps (numpy/scipy/eigen) and
-  #   also tests the automatic discovery functions in CMake (Python version, C++ standard).
-  - os: linux
-    dist: xenial # Necessary to run doxygen 1.8.15
-    name: Docs and pip
-    cache: false
-    before_install:
-    - pyenv global $(pyenv whence 2to3)  # activate all python versions
-    - PY_CMD=python3
-    - $PY_CMD -m pip install --user --upgrade pip wheel setuptools
-    install:
-    # breathe 4.14 doesn't work with bit fields. See https://github.com/michaeljones/breathe/issues/462
-    # Latest breathe + Sphinx causes warnings and errors out
-    - $PY_CMD -m pip install --user --upgrade "sphinx<3" sphinx_rtd_theme breathe==4.13.1 pytest
-    - curl -fsSL https://sourceforge.net/projects/doxygen/files/rel-1.8.15/doxygen-1.8.15.linux.bin.tar.gz/download | tar xz
-    - export PATH="$PWD/doxygen-1.8.15/bin:$PATH"
-    script:
-    - $PY_CMD -m sphinx -W -b html docs docs/.build
-    - |
-      # Make sure setup.py distributes and installs all the headers
-      $PY_CMD setup.py sdist
-      $PY_CMD -m pip install --user -U ./dist/*
-      installed=$($PY_CMD -c "import pybind11; print(pybind11.get_include(True) + '/pybind11')")
-      diff -rq $installed ./include/pybind11
-    - |
-      # Barebones build
-      cmake -DCMAKE_BUILD_TYPE=Debug -DPYBIND11_WERROR=ON -DDOWNLOAD_CATCH=ON -DPYTHON_EXECUTABLE=$(which $PY_CMD) .
-      make pytest -j 2 && make cpptest -j 2
-cache:
-  directories:
-  - $HOME/.local/bin
-  - $HOME/.local/lib
-  - $HOME/.local/include
-before_install:
-- |
-  # Configure build variables
-  set -ex
-  if [ -z "$GCC" ]; then GCC=4.8
-  else EXTRA_PACKAGES+=" g++-$GCC"
-  fi
-  export CXX=g++-$GCC CC=gcc-$GCC
-  if [ -n "$CPP" ]; then CPP=-std=c++$CPP; fi
-  if [ "${PYTHON:0:1}" = "3" ]; then PY=3; fi
-  if [ -n "$DEBUG" ]; then CMAKE_EXTRA_ARGS+=" -DCMAKE_BUILD_TYPE=Debug"; fi
-  set +ex
-- |
-  # Initialize environment
-  set -ex
-  PY_CMD=python$PYTHON
-  if [ "$TRAVIS_OS_NAME" = "osx" ]; then
-    if [ "$PY" = "3" ]; then
-      brew update && brew unlink python@2 && (brew upgrade python || brew install python)
-    else
-      curl -fsSL https://bootstrap.pypa.io/get-pip.py | $PY_CMD - --user
-    fi
-  fi
-  if [ "$PY" = 3 ] || [ -n "$PYPY" ]; then
-    $PY_CMD -m ensurepip --user
-  fi
-  $PY_CMD --version
-  $PY_CMD -m pip install --user --upgrade pip wheel
-  set +ex
-install:
-- |
-  # Install dependencies
-  set -ex
-  cmake --version
-
-  export NPY_NUM_BUILD_JOBS=2
-  local PIP_CMD=""
-  echo "Installing pytest, numpy, scipy..."
-  $PY_CMD -m pip install --user --upgrade pytest numpy scipy
-  echo "done."
-
-  mkdir eigen
-  curl -fsSL https://bitbucket.org/eigen/eigen/get/3.3.4.tar.bz2 | \
-      tar --extract -j --directory=eigen --strip-components=1
-  export CMAKE_INCLUDE_PATH="${CMAKE_INCLUDE_PATH:+$CMAKE_INCLUDE_PATH:}$PWD/eigen"
-  set +ex
-after_failure: cat tests/test_cmake_build/*.log*
diff --git a/README.md b/README.md
index ae7b01bbe0..5eee2dc9fe 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,6 @@
 [![Documentation Status](https://readthedocs.org/projects/pybind11/badge/?version=stable)](http://pybind11.readthedocs.org/en/stable/?badge=stable)
 [![Gitter chat](https://img.shields.io/gitter/room/gitterHQ/gitter.svg)](https://gitter.im/pybind/Lobby)
 [![CI](https://github.com/pybind/pybind11/workflows/CI/badge.svg)](https://github.com/pybind/pybind11/actions)
-[![Build Status](https://travis-ci.org/pybind/pybind11.svg?branch=master)](https://travis-ci.org/pybind/pybind11)
 [![Build status](https://ci.appveyor.com/api/projects/status/riaj54pn4h08xy40?svg=true)](https://ci.appveyor.com/project/wjakob/pybind11)
 
 **pybind11** is a lightweight header-only library that exposes C++ types in Python

From ff39ad3f312d949a83d2c4089c310ae6db8c7600 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 15:05:10 -0400
Subject: [PATCH 54/73] ci: include scipy for tests

---
 tests/requirements.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/requirements.txt b/tests/requirements.txt
index 9d691c036a..b0248f0103 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -2,3 +2,4 @@
 numpy; platform_python_implementation!="PyPy" or sys_platform!="darwin" or python_version<"3.0"
 numpy<1.19; platform_python_implementation=="PyPy" and sys_platform=="darwin" and python_version>="3.0"
 pytest
+scipy; (platform_python_implementation!="PyPy" or sys_platform!="darwin") and python_version<"3.9"

From 88b3e5c68d33b1f24ab72878ff61d846fccabd62 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 18:17:11 -0400
Subject: [PATCH 55/73] ci: nicer naming scheme

---
 .github/workflows/ci.yml | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5a854b6f9c..aa178f7642 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu, windows, macos]
+        runs-on: [ubuntu-latest, windows-latest, macos-latest]
         python:
         - 2.7
         - 3.5
@@ -24,30 +24,32 @@ jobs:
         - pypy3
 
         include:
-          - os: ubuntu
+          - runs-on: ubuntu-latest
             python: 3.6
-          - os: macos
+          - runs-on: macos-latest
+            python: 3.7
+          - runs-on: windows-2016
             python: 3.7
 
         exclude:
             # Currently 32bit only, and we build 64bit
-          - os: windows
+          - runs-on: windows-latest
             python: pypy2
-          - os: windows
+          - runs-on: windows-latest
             python: pypy3
 
             # Currently can't build due to warning, fixed in CPython > 3.9b5
-          - os: macos
+          - runs-on: macos-latest
             python: 3.9-dev
 
             # Currently broken on embed_test
-          - os: windows
+          - runs-on: windows-latest
             python: 3.8
-          - os: windows
+          - runs-on: windows-latest
             python: 3.9-dev
 
-    name: 🐍 ${{ matrix.python }} on ${{ matrix.os }}
-    runs-on: ${{ matrix.os }}-latest
+    name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }}"
+    runs-on: ${{ matrix.runs-on }}
 
     steps:
     - uses: actions/checkout@v2
@@ -132,7 +134,7 @@ jobs:
           - 9
           - dev
 
-    name: Clang ${{ matrix.clang }}
+    name: "🐍 3 • Clang ${{ matrix.clang }}"
     container: "silkeh/clang:${{ matrix.clang }}"
 
     steps:
@@ -171,7 +173,7 @@ jobs:
           - 7
           - latest
 
-    name: 🐍 3 GCC ${{ matrix.gcc }}
+    name: "🐍 3 • GCC ${{ matrix.gcc }}"
     container: "gcc:${{ matrix.gcc }}"
 
     steps:
@@ -258,7 +260,7 @@ jobs:
       run: cmake --build build --target test_cmake_build
 
   install-classic:
-    name: "🐍 3.5 32-bit Linux install"
+    name: "🐍 3.5 • 32-bit Linux • Install"
     runs-on: ubuntu-latest
     container: i386/debian:stretch
 
@@ -292,7 +294,7 @@ jobs:
 
 
   doxygen:
-    name: Docs test
+    name: "Documentation build test"
     runs-on: ubuntu-latest
     container: alpine:3.12
 

From a63248686542bd57244a64c7ffe058539ef542e8 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 18:42:53 -0400
Subject: [PATCH 56/73] ci: Windows 2016 test

---
 .github/workflows/ci.yml | 51 +++++++++++++++++++++++++++-------------
 1 file changed, 35 insertions(+), 16 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index aa178f7642..fc4717c168 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,6 +15,8 @@ jobs:
       fail-fast: false
       matrix:
         runs-on: [ubuntu-latest, windows-latest, macos-latest]
+        arch: [x64]
+        max-cxx-std: [17]
         python:
         - 2.7
         - 3.5
@@ -26,29 +28,45 @@ jobs:
         include:
           - runs-on: ubuntu-latest
             python: 3.6
+            arch: x64
+            max-cxx-std: 17
           - runs-on: macos-latest
             python: 3.7
+            arch: x64
+            max-cxx-std: 17
           - runs-on: windows-2016
             python: 3.7
+            arch: x86
+            max-cxx-std: 14
 
         exclude:
             # Currently 32bit only, and we build 64bit
           - runs-on: windows-latest
             python: pypy2
+            arch: x64
+            max-cxx-std: 17
           - runs-on: windows-latest
             python: pypy3
+            arch: x64
+            max-cxx-std: 17
 
             # Currently can't build due to warning, fixed in CPython > 3.9b5
           - runs-on: macos-latest
             python: 3.9-dev
+            arch: x64
+            max-cxx-std: 17
 
             # Currently broken on embed_test
           - runs-on: windows-latest
             python: 3.8
+            arch: x64
+            max-cxx-std: 17
           - runs-on: windows-latest
             python: 3.9-dev
+            arch: x64
+            max-cxx-std: 17
 
-    name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }}"
+    name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }} • ${{ matrix.arch }}"
     runs-on: ${{ matrix.runs-on }}
 
     steps:
@@ -58,6 +76,7 @@ jobs:
       uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python }}
+        architecture: ${{ matrix.arch }}
 
     - name: Cache wheels
       if: startsWith(runner.os, 'macOS')
@@ -98,27 +117,27 @@ jobs:
     - name: Interface test C++11
       run: cmake --build build --target test_cmake_build
 
-    - name: Configure C++17
+    - name: Configure C++${{ matrix.max-cxx-std }}
       shell: bash
       run: >
-        cmake -S . -B build17
+        cmake -S . -B build2
         -DPYBIND17_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=17
+        -DCMAKE_CXX_STANDARD=${{ matrix.max-cxx-std }}
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
 
-    - name: Build C++17
-      run: cmake --build build17 -j 2
+    - name: Build C++${{ matrix.max-cxx-std }}
+      run: cmake --build build2 -j 2
 
-    - name: Python tests C++17
-      run: cmake --build build17 --target pytest
+    - name: Python tests C++${{ matrix.max-cxx-std }}
+      run: cmake --build build2 --target pytest
 
-    - name: C++17 tests
-      run: cmake --build build17 --target cpptest
+    - name: C++${{ matrix.max-cxx-std }} tests
+      run: cmake --build build2 --target cpptest
 
-    - name: Interface test C++17
-      run: cmake --build build17 --target test_cmake_build
+    - name: Interface test C++${{ matrix.max-cxx-std }}
+      run: cmake --build build2 --target test_cmake_build
 
   clang:
     runs-on: ubuntu-latest
@@ -134,7 +153,7 @@ jobs:
           - 9
           - dev
 
-    name: "🐍 3 • Clang ${{ matrix.clang }}"
+    name: "🐍 3 • Clang ${{ matrix.clang }} • x64"
     container: "silkeh/clang:${{ matrix.clang }}"
 
     steps:
@@ -173,7 +192,7 @@ jobs:
           - 7
           - latest
 
-    name: "🐍 3 • GCC ${{ matrix.gcc }}"
+    name: "🐍 3 • GCC ${{ matrix.gcc }} • x64"
     container: "gcc:${{ matrix.gcc }}"
 
     steps:
@@ -221,7 +240,7 @@ jobs:
           - 7  # GCC 4.8
           - 8
 
-    name: "🐍 3 • CentOS ${{ matrix.centos }}"
+    name: "🐍 3 • CentOS ${{ matrix.centos }} • x64"
     container: "centos:${{ matrix.centos }}"
 
     steps:
@@ -260,7 +279,7 @@ jobs:
       run: cmake --build build --target test_cmake_build
 
   install-classic:
-    name: "🐍 3.5 • 32-bit Linux • Install"
+    name: "🐍 3.5 • Debian • x86 •  Install"
     runs-on: ubuntu-latest
     container: i386/debian:stretch
 

From c51b3f436d23a6d62815ba40c26d03574e1a2ea7 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Sun, 26 Jul 2020 20:25:21 -0400
Subject: [PATCH 57/73] ci: change caching

---
 .github/workflows/ci.yml |  4 +---
 tests/requirements.txt   | 11 +++++++----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index fc4717c168..9673485dd5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -87,9 +87,7 @@ jobs:
         # for ways to do this more generally
         path: ~/Library/Caches/pip
         # Look to see if there is a cache hit for the corresponding requirements file
-        key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}
-        restore-keys: |
-          ${{ runner.os }}-pip-
+        key: ${{ runner.os }}-pip-${{ matrix.python }}-${{ matrix.arch }}-${{ hashFiles('tests/requirements.txt') }}
 
     - name: Prepare env
       run: python -m pip install -r tests/requirements.txt
diff --git a/tests/requirements.txt b/tests/requirements.txt
index b0248f0103..c9750e473f 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,5 +1,8 @@
 --extra-index-url https://antocuni.github.io/pypy-wheels/manylinux2010/
-numpy; platform_python_implementation!="PyPy" or sys_platform!="darwin" or python_version<"3.0"
-numpy<1.19; platform_python_implementation=="PyPy" and sys_platform=="darwin" and python_version>="3.0"
-pytest
-scipy; (platform_python_implementation!="PyPy" or sys_platform!="darwin") and python_version<"3.9"
+numpy==1.16.6; python_version<"3.6"
+numpy==1.18.0; platform_python_implementation=="PyPy" and sys_platform=="darwin" and python_version>="3.6"
+numpy==1.19.1; (platform_python_implementation!="PyPy" or sys_platform!="darwin") and python_version>="3.6"
+pytest==4.6.9; python_version<"3.5"
+pytest==5.4.3; python_version>="3.5"
+scipy==1.2.3; (platform_python_implementation!="PyPy" or sys_platform!="darwin") and python_version<"3.6"
+scipy==1.5.2; (platform_python_implementation!="PyPy" or sys_platform!="darwin") and python_version>="3.6" and python_version<"3.9"

From 8e40e389fd60a6cdef97897b2749868004c6d994 Mon Sep 17 00:00:00 2001
From: Marcin Wojdyr <wojdyr@gmail.com>
Date: Tue, 28 Jul 2020 21:44:19 +0200
Subject: [PATCH 58/73] cast pointer to std::tuple and std::pair (#2334)

---
 include/pybind11/cast.h        | 11 +++++++++++
 tests/test_builtin_casters.cpp |  4 ++++
 tests/test_builtin_casters.py  |  3 +++
 3 files changed, 18 insertions(+)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index d788992df1..c1d0bbc34d 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -1421,6 +1421,17 @@ template <template<typename...> class Tuple, typename... Ts> class tuple_caster
         return cast_impl(std::forward<T>(src), policy, parent, indices{});
     }
 
+    // copied from the PYBIND11_TYPE_CASTER macro
+    template <typename T>
+    static handle cast(T *src, return_value_policy policy, handle parent) {
+        if (!src) return none().release();
+        if (policy == return_value_policy::take_ownership) {
+            auto h = cast(std::move(*src), policy, parent); delete src; return h;
+        } else {
+            return cast(*src, policy, parent);
+        }
+    }
+
     static constexpr auto name = _("Tuple[") + concat(make_caster<Ts>::name...) + _("]");
 
     template <typename T> using cast_op_type = type;
diff --git a/tests/test_builtin_casters.cpp b/tests/test_builtin_casters.cpp
index acb2446912..acc9f8fb36 100644
--- a/tests/test_builtin_casters.cpp
+++ b/tests/test_builtin_casters.cpp
@@ -117,12 +117,16 @@ TEST_SUBMODULE(builtin_casters, m) {
         return std::make_pair(RValueCaster{}, std::make_tuple(RValueCaster{}, std::make_pair(RValueCaster{}, RValueCaster{}))); });
     m.def("lvalue_nested", []() -> const decltype(lvnested) & { return lvnested; });
 
+    static std::pair<int, std::string> int_string_pair{2, "items"};
+    m.def("int_string_pair", []() { return &int_string_pair; });
+
     // test_builtins_cast_return_none
     m.def("return_none_string", []() -> std::string * { return nullptr; });
     m.def("return_none_char",   []() -> const char *  { return nullptr; });
     m.def("return_none_bool",   []() -> bool *        { return nullptr; });
     m.def("return_none_int",    []() -> int *         { return nullptr; });
     m.def("return_none_float",  []() -> float *       { return nullptr; });
+    m.def("return_none_pair",   []() -> std::pair<int,int> * { return nullptr; });
 
     // test_none_deferred
     m.def("defer_none_cstring", [](char *) { return false; });
diff --git a/tests/test_builtin_casters.py b/tests/test_builtin_casters.py
index a13acd5b97..af44bda71e 100644
--- a/tests/test_builtin_casters.py
+++ b/tests/test_builtin_casters.py
@@ -250,6 +250,8 @@ def test_tuple(doc):
     assert m.rvalue_nested() == ("rvalue", ("rvalue", ("rvalue", "rvalue")))
     assert m.lvalue_nested() == ("lvalue", ("lvalue", ("lvalue", "lvalue")))
 
+    assert m.int_string_pair() == (2, "items")
+
 
 def test_builtins_cast_return_none():
     """Casters produced with PYBIND11_TYPE_CASTER() should convert nullptr to None"""
@@ -258,6 +260,7 @@ def test_builtins_cast_return_none():
     assert m.return_none_bool() is None
     assert m.return_none_int() is None
     assert m.return_none_float() is None
+    assert m.return_none_pair() is None
 
 
 def test_none_deferred():

From 1491c94c9d742d2d7bfccfc57b3944d66e5e048a Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henry.fredrick.schreiner@cern.ch>
Date: Tue, 28 Jul 2020 20:13:09 -0400
Subject: [PATCH 59/73] ci: cmake Configure test (#2327)

---
 .github/workflows/configure.yml | 81 +++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 .github/workflows/configure.yml

diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
new file mode 100644
index 0000000000..a23276a346
--- /dev/null
+++ b/.github/workflows/configure.yml
@@ -0,0 +1,81 @@
+name: Configure
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+      - master
+      - stable
+      - v*
+
+jobs:
+  cmake:
+    strategy:
+      fail-fast: false
+      matrix:
+        python:
+        - 2.7
+        - 3.8
+
+    name: CMake ${{ matrix.cmake }} Python ${{ matrix.python }} on ubuntu
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Setup Python ${{ matrix.python }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python }}
+
+    - name: Prepare env
+      run: python -m pip install -r tests/requirements.txt
+
+    - name: Make build directories
+      run: |
+        mkdir build2.8
+        mkdir build3.7
+        mkdir build3.18
+
+    - name: Setup CMake 2.8
+      uses: jwlawson/actions-setup-cmake@v1.3
+      with:
+        cmake-version: 2.8
+
+    - name: Configure 2.8
+      working-directory: build2.8
+      run: >
+        cmake --version &&
+        cmake ..
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
+
+    - name: Setup CMake 3.7
+      uses: jwlawson/actions-setup-cmake@v1.3
+      with:
+        cmake-version: 3.7
+
+    - name: Configure 3.7
+      working-directory: build3.7
+      run: >
+        cmake --version &&
+        cmake ..
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
+
+    - name: Setup CMake 3.18
+      uses: jwlawson/actions-setup-cmake@v1.3
+      with:
+        cmake-version: 3.18
+
+    - name: Configure 3.18
+      working-directory: build3.18
+      run: >
+        cmake --version &&
+        cmake ..
+        -DPYBIND11_WERROR=ON
+        -DDOWNLOAD_CATCH=ON
+        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")

From 6ec1775fffa9918ffdfdf7d2c8c08a1117c6da7c Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Tue, 28 Jul 2020 00:43:12 -0400
Subject: [PATCH 60/73] feat: drop CMake 3.6 and below, modernize CMake

fix: include PYTHON_IS_DEBUG
---
 .github/workflows/ci.yml                      |   4 -
 .github/workflows/configure.yml               |  21 +-
 CMakeLists.txt                                | 312 +++++++++++-------
 docs/compiling.rst                            |  50 +--
 include/pybind11/detail/common.h              |   9 +-
 tests/CMakeLists.txt                          |  53 +--
 tests/test_cmake_build/CMakeLists.txt         |  24 +-
 .../installed_embed/CMakeLists.txt            |  10 +-
 .../installed_function/CMakeLists.txt         |   2 +-
 .../installed_target/CMakeLists.txt           |  10 +-
 .../subdirectory_embed/CMakeLists.txt         |  12 +-
 .../subdirectory_function/CMakeLists.txt      |   2 +-
 .../subdirectory_target/CMakeLists.txt        |  10 +-
 tests/test_embed/CMakeLists.txt               |  22 +-
 tools/pybind11Config.cmake.in                 |   9 +-
 tools/pybind11Tools.cmake                     | 146 +++-----
 16 files changed, 333 insertions(+), 363 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9673485dd5..bf0879db1f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -95,7 +95,6 @@ jobs:
     - name: Configure C++11
       shell: bash
       run: >
-        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -163,7 +162,6 @@ jobs:
     - name: Configure
       shell: bash
       run: >
-        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -210,7 +208,6 @@ jobs:
     - name: Configure
       shell: bash
       run: >
-        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -256,7 +253,6 @@ jobs:
     - name: Configure
       shell: bash
       run: >
-        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
diff --git a/.github/workflows/configure.yml b/.github/workflows/configure.yml
index a23276a346..96904341de 100644
--- a/.github/workflows/configure.yml
+++ b/.github/workflows/configure.yml
@@ -34,33 +34,31 @@ jobs:
 
     - name: Make build directories
       run: |
-        mkdir build2.8
         mkdir build3.7
+        mkdir build3.11
         mkdir build3.18
 
-    - name: Setup CMake 2.8
+    - name: Setup CMake 3.7
       uses: jwlawson/actions-setup-cmake@v1.3
       with:
-        cmake-version: 2.8
+        cmake-version: 3.7
 
-    - name: Configure 2.8
-      working-directory: build2.8
+    - name: Configure 3.7
+      working-directory: build3.7
       run: >
-        cmake --version &&
         cmake ..
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
 
-    - name: Setup CMake 3.7
+    - name: Setup CMake 3.11
       uses: jwlawson/actions-setup-cmake@v1.3
       with:
-        cmake-version: 3.7
+        cmake-version: 3.11
 
-    - name: Configure 3.7
-      working-directory: build3.7
+    - name: Configure 3.11
+      working-directory: build3.11
       run: >
-        cmake --version &&
         cmake ..
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -74,7 +72,6 @@ jobs:
     - name: Configure 3.18
       working-directory: build3.18
       run: >
-        cmake --version &&
         cmake ..
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 85ecd9028f..2227559da3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,31 +5,102 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.7)
 
-if (POLICY CMP0048)
-  # cmake warns if loaded from a min-3.0-required parent dir, so silence the warning:
-  cmake_policy(SET CMP0048 NEW)
-endif()
-
-# CMake versions < 3.4.0 do not support try_compile/pthread checks without C as active language.
-if(CMAKE_VERSION VERSION_LESS 3.4.0)
-  project(pybind11)
+# VERSION 3.7...3.18, but some versions of VS have a patched CMake 3.11
+# that do not work properly with this syntax, so using the following workaround:
+if(${CMAKE_VERSION} VERSION_LESS 3.18)
+    cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  project(pybind11 CXX)
+    cmake_policy(VERSION 3.18)
 endif()
 
+# Extract project version from source
+file(
+  STRINGS
+    "${CMAKE_CURRENT_SOURCE_DIR}/include/pybind11/detail/common.h"
+  pybind11_version_defines
+  REGEX
+    "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH|TYPE) ")
+
+foreach(ver ${pybind11_version_defines})
+    if (ver MATCHES [=[#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH|TYPE) +"?([^ ^"]+)"?$]=])
+        set(PYBIND11_VERSION_${CMAKE_MATCH_1} "${CMAKE_MATCH_2}")
+    endif()
+endforeach()
+
+project(
+    pybind11
+  LANGUAGES
+    CXX
+  VERSION
+    "${PYBIND11_VERSION_MAJOR}.${PYBIND11_VERSION_MINOR}.${PYBIND11_VERSION_PATCH}"
+)
+
+# Standard includes
+include(GNUInstallDirs)
+include(CMakePackageConfigHelpers)
+include(CMakeDependentOption)
+
 # Check if pybind11 is being used directly or via add_subdirectory
-set(PYBIND11_MASTER_PROJECT OFF)
-if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
-  set(PYBIND11_MASTER_PROJECT ON)
+if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+    set(PYBIND11_MASTER_PROJECT ON)
+    message(STATUS "pybind11 v${pybind11_VERSION} ${PYBIND11_VERSION_TYPE}")
+    message(STATUS "CMake ${CMAKE_VERSION}")
+
+    if(CMAKE_CXX_STANDARD)
+        set(CMAKE_CXX_EXTENSIONS OFF)
+        set(CMAKE_CXX_STANDARD_REQUIRED ON)
+    endif()
+else()
+    set(PYBIND11_MASTER_PROJECT OFF)
+    set(pybind11_system SYSTEM)
 endif()
 
 option(PYBIND11_INSTALL "Install pybind11 header files?" ${PYBIND11_MASTER_PROJECT})
-option(PYBIND11_TEST    "Build pybind11 test suite?"     ${PYBIND11_MASTER_PROJECT})
+option(PYBIND11_TEST "Build pybind11 test suite?" ${PYBIND11_MASTER_PROJECT})
+option(PYBIND11_CLASSIC_LTO "Use the classic LTO flag algorithm, even on CMake 3.9+" OFF)
+cmake_dependent_option(
+    USE_PYTHON_INCLUDE_DIR
+    "Install pybind11 headers in Python include directory instead of default installation prefix" OFF
+    "PYBIND11_INSTALL" OFF
+)
+
+# NB: when adding a header don't forget to also add it to setup.py
+set(PYBIND11_HEADERS
+    include/pybind11/detail/class.h
+    include/pybind11/detail/common.h
+    include/pybind11/detail/descr.h
+    include/pybind11/detail/init.h
+    include/pybind11/detail/internals.h
+    include/pybind11/detail/typeid.h
+    include/pybind11/attr.h
+    include/pybind11/buffer_info.h
+    include/pybind11/cast.h
+    include/pybind11/chrono.h
+    include/pybind11/common.h
+    include/pybind11/complex.h
+    include/pybind11/options.h
+    include/pybind11/eigen.h
+    include/pybind11/embed.h
+    include/pybind11/eval.h
+    include/pybind11/functional.h
+    include/pybind11/numpy.h
+    include/pybind11/operators.h
+    include/pybind11/pybind11.h
+    include/pybind11/pytypes.h
+    include/pybind11/stl.h
+    include/pybind11/stl_bind.h
+)
+# cmake 3.12 added list(TRANSFORM <list> PREPEND
+# But we can't use it yet
+string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/"
+       PYBIND11_HEADERS "${PYBIND11_HEADERS}")
 
-list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/tools")
 
+# Classic mode
+
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/tools")
 include(pybind11Tools)
 
 # Cache variables so pybind11_add_module can be used in parent projects
@@ -40,118 +111,131 @@ set(PYTHON_MODULE_PREFIX ${PYTHON_MODULE_PREFIX} CACHE INTERNAL "")
 set(PYTHON_MODULE_EXTENSION ${PYTHON_MODULE_EXTENSION} CACHE INTERNAL "")
 set(PYTHON_VERSION_MAJOR ${PYTHON_VERSION_MAJOR} CACHE INTERNAL "")
 set(PYTHON_VERSION_MINOR ${PYTHON_VERSION_MINOR} CACHE INTERNAL "")
+set(PYTHON_IS_DEBUG "${PYTHON_IS_DEBUG}" CACHE INTERNAL "")
 
-# NB: when adding a header don't forget to also add it to setup.py
-set(PYBIND11_HEADERS
-  include/pybind11/detail/class.h
-  include/pybind11/detail/common.h
-  include/pybind11/detail/descr.h
-  include/pybind11/detail/init.h
-  include/pybind11/detail/internals.h
-  include/pybind11/detail/typeid.h
-  include/pybind11/attr.h
-  include/pybind11/buffer_info.h
-  include/pybind11/cast.h
-  include/pybind11/chrono.h
-  include/pybind11/common.h
-  include/pybind11/complex.h
-  include/pybind11/options.h
-  include/pybind11/eigen.h
-  include/pybind11/embed.h
-  include/pybind11/eval.h
-  include/pybind11/functional.h
-  include/pybind11/numpy.h
-  include/pybind11/operators.h
-  include/pybind11/pybind11.h
-  include/pybind11/pytypes.h
-  include/pybind11/stl.h
-  include/pybind11/stl_bind.h
-)
-string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/"
-       PYBIND11_HEADERS "${PYBIND11_HEADERS}")
 
-if (PYBIND11_TEST)
-  add_subdirectory(tests)
+if(PYBIND11_TEST OR (BUILD_TESTING AND PYBIND11_MASTER_PROJECT))
+    add_subdirectory(tests)
 endif()
 
-include(GNUInstallDirs)
-include(CMakePackageConfigHelpers)
 
-# extract project version from source
-file(STRINGS "${PYBIND11_INCLUDE_DIR}/pybind11/detail/common.h" pybind11_version_defines
-     REGEX "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) ")
-foreach(ver ${pybind11_version_defines})
-  if (ver MATCHES "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) +([^ ]+)$")
-    set(PYBIND11_VERSION_${CMAKE_MATCH_1} "${CMAKE_MATCH_2}" CACHE INTERNAL "")
-  endif()
-endforeach()
-set(${PROJECT_NAME}_VERSION ${PYBIND11_VERSION_MAJOR}.${PYBIND11_VERSION_MINOR}.${PYBIND11_VERSION_PATCH})
-message(STATUS "pybind11 v${${PROJECT_NAME}_VERSION}")
-
-option (USE_PYTHON_INCLUDE_DIR "Install pybind11 headers in Python include directory instead of default installation prefix" OFF)
-if (USE_PYTHON_INCLUDE_DIR)
+if(USE_PYTHON_INCLUDE_DIR)
     file(RELATIVE_PATH CMAKE_INSTALL_INCLUDEDIR ${CMAKE_INSTALL_PREFIX} ${PYTHON_INCLUDE_DIRS})
 endif()
 
-if(NOT (CMAKE_VERSION VERSION_LESS 3.0))  # CMake >= 3.0
-  # Build an interface library target:
-  add_library(pybind11 INTERFACE)
-  add_library(pybind11::pybind11 ALIAS pybind11)  # to match exported target
-  target_include_directories(pybind11 INTERFACE $<BUILD_INTERFACE:${PYBIND11_INCLUDE_DIR}>
-                                                $<BUILD_INTERFACE:${PYTHON_INCLUDE_DIRS}>
-                                                $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
-  target_compile_options(pybind11 INTERFACE $<BUILD_INTERFACE:${PYBIND11_CPP_STANDARD}>)
-
-  add_library(module INTERFACE)
-  add_library(pybind11::module ALIAS module)
-  if(NOT MSVC)
-    target_compile_options(module INTERFACE -fvisibility=hidden)
-  endif()
-  target_link_libraries(module INTERFACE pybind11::pybind11)
-  if(WIN32 OR CYGWIN)
-    target_link_libraries(module INTERFACE $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
-  elseif(APPLE)
-    target_link_libraries(module INTERFACE "-undefined dynamic_lookup")
-  endif()
-
-  add_library(embed INTERFACE)
-  add_library(pybind11::embed ALIAS embed)
-  target_link_libraries(embed INTERFACE pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
+# Note: when creating targets, you cannot use if statements at configure time -
+# you need generator expressions, because those will be placed in the target file.
+
+# Build an interface library target:
+add_library(pybind11 INTERFACE)
+add_library(pybind11::pybind11 ALIAS pybind11)  # to match exported target
+
+target_include_directories(pybind11 ${pybind11_system} INTERFACE $<BUILD_INTERFACE:${PYBIND11_INCLUDE_DIR}>
+                                                                 $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
+# Only add Python for build - must be added during the import for config since it has to be re-discovered.
+target_include_directories(pybind11 SYSTEM INTERFACE $<BUILD_INTERFACE:${PYTHON_INCLUDE_DIRS}>)
+
+if(CMAKE_VERSION VERSION_LESS 3.13)
+    target_compile_features(
+        pybind11
+      INTERFACE
+        cxx_auto_type
+        cxx_constexpr
+        cxx_defaulted_functions
+        cxx_lambdas
+        cxx_nullptr
+        cxx_range_for
+        cxx_right_angle_brackets
+        cxx_strong_enums
+        cxx_user_literals
+        cxx_variadic_templates
+      )
+else()
+    # This was added in CMake 3.8, but we are keeping a consistent breaking
+    # point for the config file at 3.13. A config generated by CMake 3.13+
+    # can ony be read in 3.13+ due to the SHELL usage later, so this is safe to do.
+    target_compile_features(pybind11 INTERFACE cxx_std_11)
+endif()
+
+add_library(module INTERFACE)
+add_library(pybind11::module ALIAS module)
+
+target_link_libraries(module INTERFACE pybind11::pybind11)
+
+# See https://github.com/Kitware/CMake/blob/master/Modules/CMakePlatformId.h.in for platform IDs
+# Note: CMake 3.15 allows $<PLATFORM_ID:Windows,Cygwin>
+target_link_libraries(module INTERFACE "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>")
+
+if(CMAKE_VERSION VERSION_LESS 3.13)
+    target_link_libraries(module INTERFACE "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
+else()
+    # SHELL (3.12+) forces this to remain together, and link_options was added in 3.13+
+    target_link_options(module INTERFACE "$<$<PLATFORM_ID:Darwin>:SHELL:-undefined dynamic_lookup>")
 endif()
 
-if (PYBIND11_INSTALL)
-  install(DIRECTORY ${PYBIND11_INCLUDE_DIR}/pybind11 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
-  # GNUInstallDirs "DATADIR" wrong here; CMake search path wants "share".
-  set(PYBIND11_CMAKECONFIG_INSTALL_DIR "share/cmake/${PROJECT_NAME}" CACHE STRING "install path for pybind11Config.cmake")
-
-  configure_package_config_file(tools/${PROJECT_NAME}Config.cmake.in
-                                "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
-                                INSTALL_DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
-  # Remove CMAKE_SIZEOF_VOID_P from ConfigVersion.cmake since the library does
-  # not depend on architecture specific settings or libraries.
-  set(_PYBIND11_CMAKE_SIZEOF_VOID_P ${CMAKE_SIZEOF_VOID_P})
-  unset(CMAKE_SIZEOF_VOID_P)
-  write_basic_package_version_file(${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-                                   VERSION ${${PROJECT_NAME}_VERSION}
-                                   COMPATIBILITY AnyNewerVersion)
-  set(CMAKE_SIZEOF_VOID_P ${_PYBIND11_CMAKE_SIZEOF_VOID_P})
-  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
-                ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-                tools/FindPythonLibsNew.cmake
-                tools/pybind11Tools.cmake
-          DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
-
-  if(NOT (CMAKE_VERSION VERSION_LESS 3.0))
+
+message(STATUS "CXX Compiler version: ${CMAKE_CXX_COMPILER_VERSION}")
+
+set(clang_4plus "$<AND:$<CXX_COMPILER_ID:Clang>,$<NOT:$<VERSION_LESS:$<CXX_COMPILER_VERSION>,3.9>>>")
+set(no_register "$<OR:${clang_4plus},$<CXX_COMPILER_ID:AppleClang>>")
+target_compile_options(pybind11 INTERFACE "$<${no_register}:-Wno-register;-Wno-deprecated-register>")
+
+add_library(embed INTERFACE)
+add_library(pybind11::embed ALIAS embed)
+target_link_libraries(embed INTERFACE pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
+
+if(PYBIND11_INSTALL)
+    install(DIRECTORY ${PYBIND11_INCLUDE_DIR}/pybind11 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+    # GNUInstallDirs "DATADIR" wrong here; CMake search path wants "share".
+    set(PYBIND11_CMAKECONFIG_INSTALL_DIR "share/cmake/${PROJECT_NAME}" CACHE STRING "install path for pybind11Config.cmake")
+
+    configure_package_config_file(tools/${PROJECT_NAME}Config.cmake.in
+                                  "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
+                                  INSTALL_DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
+
+    if(CMAKE_VERSION VERSION_LESS 3.14)
+        # Remove CMAKE_SIZEOF_VOID_P from ConfigVersion.cmake since the library does
+        # not depend on architecture specific settings or libraries.
+        set(_PYBIND11_CMAKE_SIZEOF_VOID_P ${CMAKE_SIZEOF_VOID_P})
+        unset(CMAKE_SIZEOF_VOID_P)
+
+        write_basic_package_version_file(
+            ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+          VERSION
+            ${PROJECT_VERSION}
+          COMPATIBILITY
+            AnyNewerVersion
+        )
+
+        set(CMAKE_SIZEOF_VOID_P ${_PYBIND11_CMAKE_SIZEOF_VOID_P})
+    else()
+        write_basic_package_version_file(
+            ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+          VERSION
+            ${PROJECT_VERSION}
+          COMPATIBILITY
+            AnyNewerVersion
+          ARCH_INDEPENDENT
+        )
+    endif()
+
+    install(
+      FILES
+        ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
+        ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+        tools/FindPythonLibsNew.cmake
+        tools/pybind11Tools.cmake
+      DESTINATION
+        ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
+
     if(NOT PYBIND11_EXPORT_NAME)
-      set(PYBIND11_EXPORT_NAME "${PROJECT_NAME}Targets")
+        set(PYBIND11_EXPORT_NAME "${PROJECT_NAME}Targets")
     endif()
 
     install(TARGETS pybind11 module embed
             EXPORT "${PYBIND11_EXPORT_NAME}")
-    if(PYBIND11_MASTER_PROJECT)
-      install(EXPORT "${PYBIND11_EXPORT_NAME}"
-              NAMESPACE "${PROJECT_NAME}::"
-              DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
-    endif()
-  endif()
+
+    install(EXPORT "${PYBIND11_EXPORT_NAME}"
+            NAMESPACE "pybind11::"
+            DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
 endif()
diff --git a/docs/compiling.rst b/docs/compiling.rst
index bfb1cd8056..dce44c8791 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -33,7 +33,7 @@ extension module can be created with just a few lines of code:
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 2.8.12)
+    cmake_minimum_required(VERSION 3.7)
     project(example)
 
     add_subdirectory(pybind11)
@@ -59,7 +59,7 @@ function with the following signature:
 .. code-block:: cmake
 
     pybind11_add_module(<name> [MODULE | SHARED] [EXCLUDE_FROM_ALL]
-                        [NO_EXTRAS] [SYSTEM] [THIN_LTO] source1 [source2 ...])
+                        [NO_EXTRAS] [THIN_LTO] source1 [source2 ...])
 
 This function behaves very much like CMake's builtin ``add_library`` (in fact,
 it's a wrapper function around that command). It will add a library target
@@ -86,10 +86,6 @@ latter optimizations are never applied in ``Debug`` mode.  If ``NO_EXTRAS`` is
 given, they will always be disabled, even in ``Release`` mode. However, this
 will result in code bloat and is generally not recommended.
 
-By default, pybind11 and Python headers will be included with ``-I``. In order
-to include pybind11 as system library, e.g. to avoid warnings in downstream
-code with warn-levels outside of pybind11's scope, set the option ``SYSTEM``.
-
 As stated above, LTO is enabled by default. Some newer compilers also support
 different flavors of LTO such as `ThinLTO`_. Setting ``THIN_LTO`` will cause
 the function to prefer this flavor if available. The function falls back to
@@ -100,25 +96,22 @@ regular LTO if ``-flto=thin`` is not available.
 Configuration variables
 -----------------------
 
-By default, pybind11 will compile modules with the C++14 standard, if available
-on the target compiler, falling back to C++11 if C++14 support is not
-available.  Note, however, that this default is subject to change: future
-pybind11 releases are expected to migrate to newer C++ standards as they become
-available.  To override this, the standard flag can be given explicitly in
-`CMAKE_CXX_STANDARD <https://cmake.org/cmake/help/v3.17/variable/CMAKE_CXX_STANDARD.html>`_:
+By default, pybind11 will compile modules with the compiler default or the
+minimum standard required by PyBind11, whichever is higher.  You can set the
+standard explicitly with
+`CMAKE_CXX_STANDARD <https://cmake.org/cmake/help/latest/variable/CMAKE_CXX_STANDARD.html>`_:
 
 .. code-block:: cmake
 
     # Use just one of these:
-    set(CMAKE_CXX_STANDARD 11)
     set(CMAKE_CXX_STANDARD 14)
-    set(CMAKE_CXX_STANDARD 17) # Experimental C++17 support
+    set(CMAKE_CXX_STANDARD 17)
 
-    add_subdirectory(pybind11)  # or find_package(pybind11)
 
-Note that this and all other configuration variables must be set **before** the
-call to ``add_subdirectory`` or ``find_package``. The variables can also be set
-when calling CMake from the command line using the ``-D<variable>=<value>`` flag.
+The variables can also be set when calling CMake from the command line using
+the ``-D<variable>=<value>`` flag. You can also manually set ``CXX_STANDARD``
+on a target or use ``target_compile_features`` on your targets - anything that
+CMake supports.
 
 The target Python version can be selected by setting ``PYBIND11_PYTHON_VERSION``
 or an exact Python installation can be specified with ``PYTHON_EXECUTABLE``.
@@ -128,7 +121,7 @@ For example:
 
     cmake -DPYBIND11_PYTHON_VERSION=3.6 ..
     # or
-    cmake -DPYTHON_EXECUTABLE=path/to/python ..
+    cmake -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") ..
 
 find_package vs. add_subdirectory
 ---------------------------------
@@ -139,7 +132,7 @@ See the `Config file`_ docstring for details of relevant CMake variables.
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 2.8.12)
+    cmake_minimum_required(VERSION 3.7)
     project(example)
 
     find_package(pybind11 REQUIRED)
@@ -171,13 +164,13 @@ Advanced: interface library target
 When using a version of CMake greater than 3.0, pybind11 can additionally
 be used as a special *interface library* . The target ``pybind11::module``
 is available with pybind11 headers, Python headers and libraries as needed,
-and C++ compile definitions attached. This target is suitable for linking
+and C++ compile features attached. This target is suitable for linking
 to an independently constructed (through ``add_library``, not
 ``pybind11_add_module``) target in the consuming project.
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.0)
+    cmake_minimum_required(VERSION 3.7)
     project(example)
 
     find_package(pybind11 REQUIRED)  # or add_subdirectory(pybind11)
@@ -201,6 +194,17 @@ to an independently constructed (through ``add_library``, not
     Studio (``/bigobj``).  The :ref:`FAQ <faq:symhidden>` contains an
     explanation on why these are needed.
 
+    If you want to add these in yourself, you can use:
+
+    .. code-block:: cmake
+
+        cmake_minimum_required(3.9)
+        set(CMAKE_CXX_VISIBILITY_PRESET hidden)
+        set(CMAKE_INTERPROCEDURAL_OPTIMIZATION ON)
+
+    or set teh corisponding property (without the ``CMAKE_``) on the targets
+    manually.
+
 Embedding the Python interpreter
 --------------------------------
 
@@ -213,7 +217,7 @@ information about usage in C++, see :doc:`/advanced/embedding`.
 
 .. code-block:: cmake
 
-    cmake_minimum_required(VERSION 3.0)
+    cmake_minimum_required(VERSION 3.7)
     project(example)
 
     find_package(pybind11 REQUIRED)  # or add_subdirectory(pybind11)
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 33805e0f91..2d83e482df 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -9,6 +9,11 @@
 
 #pragma once
 
+#define PYBIND11_VERSION_MAJOR 2
+#define PYBIND11_VERSION_MINOR 6
+#define PYBIND11_VERSION_PATCH 0
+#define PYBIND11_VERSION_TYPE "dev"
+
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }
 
@@ -96,10 +101,6 @@
 #  define PYBIND11_MAYBE_UNUSED __attribute__ ((__unused__))
 #endif
 
-#define PYBIND11_VERSION_MAJOR 2
-#define PYBIND11_VERSION_MINOR 5
-#define PYBIND11_VERSION_PATCH dev1
-
 /* Don't let Python.h #define (v)snprintf as macro because they are implemented
    properly in Visual Studio since 2015. */
 #if defined(_MSC_VER) && _MSC_VER >= 1900
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index fda6aac8a9..37a8b81b81 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -5,16 +5,26 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.7)
+
+# VERSION 3.7...3.18, but some versions of VS have a patched CMake 3.11
+# that do not work properly with this syntax, so using the following workaround:
+if(${CMAKE_VERSION} VERSION_LESS 3.18)
+    cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
+else()
+    cmake_policy(VERSION 3.18)
+endif()
+
+# There's no harm in including a project in a project
+project(pybind11_tests CXX)
 
 option(PYBIND11_WERROR  "Report all warnings as errors"  OFF)
+option(DOWNLOAD_EIGEN "Download EIGEN (requires CMake 3.11+)" OFF)
 set(PYBIND11_TEST_OVERRIDE "" CACHE STRING "Tests from ;-separated list of *.cpp files will be built instead of all tests")
 
-if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
     # We're being loaded directly, i.e. not via add_subdirectory, so make this
     # work as its own project and load the pybind11Config to get the tools we need
-    project(pybind11_tests CXX)
-
     find_package(pybind11 REQUIRED CONFIG)
 endif()
 
@@ -97,8 +107,6 @@ set(PYBIND11_CROSS_MODULE_GIL_TESTS
   test_gil_scoped.py
 )
 
-option(DOWNLOAD_EIGEN "Download EIGEN (requires CMake 3.11+)" OFF)
-
 # Check if Eigen is available; if not, remove from PYBIND11_TEST_FILES (but
 # keep it in PYBIND11_PYTEST_FILES, so that we get the "eigen is not installed"
 # skip message).
@@ -130,14 +138,13 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     set(EIGEN3_INCLUDE_DIR ${eigen_SOURCE_DIR})
     set(EIGEN3_FOUND TRUE)
   else()
-    if (NOT CMAKE_VERSION VERSION_LESS 3.0)
-      find_package(Eigen3 3.2.7 QUIET CONFIG)
-      if (EIGEN3_FOUND)
-        if (EIGEN3_VERSION_STRING AND NOT EIGEN3_VERSION_STRING VERSION_LESS 3.3.1)
-          set(PYBIND11_EIGEN_VIA_TARGET TRUE)
-        endif()
+    find_package(Eigen3 3.2.7 QUIET CONFIG)
+    if (EIGEN3_FOUND)
+      if (EIGEN3_VERSION_STRING AND NOT EIGEN3_VERSION_STRING VERSION_LESS 3.3.1)
+        set(PYBIND11_EIGEN_VIA_TARGET TRUE)
       endif()
     endif()
+
     if (NOT EIGEN3_FOUND)
       # Couldn't load via target, so fall back to allowing module mode finding, which will pick up
       # tools/FindEigen3.cmake
@@ -178,6 +185,7 @@ function(pybind11_enable_warnings target_name)
     endif()
   endif()
 
+  # Needs to be readded since the ordering requires these to be after the ones above
   if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
     if(CMAKE_CXX_STANDARD LESS 17)
       target_compile_options(${target_name} PUBLIC -Wno-deprecated-register)
@@ -259,15 +267,9 @@ if(NOT PYBIND11_PYTEST_FOUND)
   set(PYBIND11_PYTEST_FOUND TRUE CACHE INTERNAL "")
 endif()
 
-if(CMAKE_VERSION VERSION_LESS 3.2)
-  set(PYBIND11_USES_TERMINAL "")
-else()
-  set(PYBIND11_USES_TERMINAL "USES_TERMINAL")
-endif()
-
 # A single command to compile and run the tests
 add_custom_target(pytest COMMAND ${PYTHON_EXECUTABLE} -m pytest ${PYBIND11_PYTEST_FILES}
-                  DEPENDS ${test_targets} WORKING_DIRECTORY ${testdir} ${PYBIND11_USES_TERMINAL})
+                  DEPENDS ${test_targets} WORKING_DIRECTORY ${testdir} USES_TERMINAL)
 
 if(PYBIND11_TEST_OVERRIDE)
   add_custom_command(TARGET pytest POST_BUILD
@@ -279,14 +281,19 @@ add_custom_target(check DEPENDS pytest)
 
 # The remaining tests only apply when being built as part of the pybind11 project, but not if the
 # tests are being built independently.
-if (NOT PROJECT_NAME STREQUAL "pybind11")
+if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
   return()
 endif()
 
 # Add a post-build comment to show the primary test suite .so size and, if a previous size, compare it:
-add_custom_command(TARGET pybind11_tests POST_BUILD
-  COMMAND ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/tools/libsize.py
-  $<TARGET_FILE:pybind11_tests> ${CMAKE_CURRENT_BINARY_DIR}/sosize-$<TARGET_FILE_NAME:pybind11_tests>.txt)
+add_custom_command(
+  TARGET
+    pybind11_tests
+  POST_BUILD COMMAND
+    ${PYTHON_EXECUTABLE}
+    ${CMAKE_CURRENT_SOURCE_DIR}/../tools/libsize.py
+    $<TARGET_FILE:pybind11_tests>
+    ${CMAKE_CURRENT_BINARY_DIR}/sosize-$<TARGET_FILE_NAME:pybind11_tests>.txt)
 
 # Test embedding the interpreter. Provides the `cpptest` target.
 add_subdirectory(test_embed)
diff --git a/tests/test_cmake_build/CMakeLists.txt b/tests/test_cmake_build/CMakeLists.txt
index cf9a9ca9ff..fd8c80304a 100644
--- a/tests/test_cmake_build/CMakeLists.txt
+++ b/tests/test_cmake_build/CMakeLists.txt
@@ -1,26 +1,22 @@
 add_custom_target(test_cmake_build)
 
-if(CMAKE_VERSION VERSION_LESS 3.1)
-  # 3.0 needed for interface library for subdirectory_target/installed_target
-  # 3.1 needed for cmake -E env for testing
-  return()
-endif()
 
-include(CMakeParseArguments)
 function(pybind11_add_build_test name)
   cmake_parse_arguments(ARG "INSTALL" "" "" ${ARGN})
 
-  set(build_options "-DCMAKE_PREFIX_PATH=${PROJECT_BINARY_DIR}/mock_install"
+  set(build_options "-DCMAKE_PREFIX_PATH=${pybind11_BINARY_DIR}/mock_install"
                     "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
-                    "-DPYTHON_EXECUTABLE:FILEPATH=${PYTHON_EXECUTABLE}"
-                    "-DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}"
-                    "-DPYBIND11_CPP_STANDARD=${PYBIND11_CPP_STANDARD}")
+                    "-DPYTHON_EXECUTABLE:FILEPATH=${PYTHON_EXECUTABLE}")
+
+  if(CMAKE_CXX_STANDARD)
+    list(APPEND build_options "-DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}")
+  endif()
+
   if(NOT ARG_INSTALL)
-    list(APPEND build_options "-DPYBIND11_PROJECT_DIR=${PROJECT_SOURCE_DIR}")
+    list(APPEND build_options "-DPYBIND11_PROJECT_DIR=${pybind11_SOURCE_DIR}")
   endif()
 
   add_custom_target(test_${name} ${CMAKE_CTEST_COMMAND}
-    --quiet --output-log ${name}.log
     --build-and-test "${CMAKE_CURRENT_SOURCE_DIR}/${name}"
                      "${CMAKE_CURRENT_BINARY_DIR}/${name}"
     --build-config Release
@@ -45,8 +41,8 @@ endif()
 
 if(PYBIND11_INSTALL)
   add_custom_target(mock_install ${CMAKE_COMMAND}
-    "-DCMAKE_INSTALL_PREFIX=${PROJECT_BINARY_DIR}/mock_install"
-    -P "${PROJECT_BINARY_DIR}/cmake_install.cmake"
+    "-DCMAKE_INSTALL_PREFIX=${pybind11_BINARY_DIR}/mock_install"
+    -P "${pybind11_BINARY_DIR}/cmake_install.cmake"
   )
 
   pybind11_add_build_test(installed_function INSTALL)
diff --git a/tests/test_cmake_build/installed_embed/CMakeLists.txt b/tests/test_cmake_build/installed_embed/CMakeLists.txt
index 6ab3efd470..80ac2f0e92 100644
--- a/tests/test_cmake_build/installed_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_embed/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.7)
 project(test_installed_embed CXX)
 
 set(CMAKE_MODULE_PATH "")
@@ -14,11 +14,3 @@ target_link_libraries(test_cmake_build PRIVATE pybind11::embed)
 set_target_properties(test_cmake_build PROPERTIES NO_SYSTEM_FROM_IMPORTED ON)
 
 add_custom_target(check $<TARGET_FILE:test_cmake_build> ${PROJECT_SOURCE_DIR}/../test.py)
-
-if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
-  if(CMAKE_CXX_STANDARD LESS 17)
-    target_compile_options(test_cmake_build PUBLIC -Wno-deprecated-register)
-  else()
-    target_compile_options(test_cmake_build PUBLIC -Wno-register)
-  endif()
-endif()
diff --git a/tests/test_cmake_build/installed_function/CMakeLists.txt b/tests/test_cmake_build/installed_function/CMakeLists.txt
index e0c20a8a36..a8c0130d91 100644
--- a/tests/test_cmake_build/installed_function/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_function/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.7)
 project(test_installed_module CXX)
 
 set(CMAKE_MODULE_PATH "")
diff --git a/tests/test_cmake_build/installed_target/CMakeLists.txt b/tests/test_cmake_build/installed_target/CMakeLists.txt
index 38520fa9c0..a172c20cfd 100644
--- a/tests/test_cmake_build/installed_target/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_target/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.7)
 project(test_installed_target CXX)
 
 set(CMAKE_MODULE_PATH "")
@@ -20,11 +20,3 @@ set_target_properties(test_cmake_build PROPERTIES NO_SYSTEM_FROM_IMPORTED ON)
 
 add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
                   ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME})
-
-if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
-  if(CMAKE_CXX_STANDARD LESS 17)
-    target_compile_options(test_cmake_build PUBLIC -Wno-deprecated-register)
-  else()
-    target_compile_options(test_cmake_build PUBLIC -Wno-register)
-  endif()
-endif()
diff --git a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
index 003e93c22e..170ec5300d 100644
--- a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.7)
 project(test_subdirectory_embed CXX)
 
 set(PYBIND11_INSTALL ON CACHE BOOL "")
@@ -23,13 +23,3 @@ install(TARGETS test_embed_lib
         RUNTIME DESTINATION lib)
 install(EXPORT      test_export
         DESTINATION lib/cmake/test_export/test_export-Targets.cmake)
-
-if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
-  if(CMAKE_CXX_STANDARD LESS 17)
-    target_compile_options(test_embed_lib PUBLIC -Wno-deprecated-register)
-    target_compile_options(test_cmake_build PUBLIC -Wno-deprecated-register)
-  else()
-    target_compile_options(test_embed_lib PUBLIC -Wno-register)
-    target_compile_options(test_cmake_build PUBLIC -Wno-register)
-  endif()
-endif()
diff --git a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
index 278007aebd..f4d4e35833 100644
--- a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.7)
 project(test_subdirectory_module CXX)
 
 add_subdirectory(${PYBIND11_PROJECT_DIR} pybind11)
diff --git a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
index 507cb8b99a..01acba426f 100644
--- a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.0)
+cmake_minimum_required(VERSION 3.7)
 project(test_subdirectory_target CXX)
 
 add_subdirectory(${PYBIND11_PROJECT_DIR} pybind11)
@@ -13,11 +13,3 @@ set_target_properties(test_cmake_build PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX
 
 add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
                   ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME})
-
-if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
-  if(CMAKE_CXX_STANDARD LESS 17)
-    target_compile_options(test_cmake_build PUBLIC -Wno-deprecated-register)
-  else()
-    target_compile_options(test_cmake_build PUBLIC -Wno-register)
-  endif()
-endif()
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index 1e0ebde745..495b0fcbfa 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -20,18 +20,12 @@ add_executable(test_embed
 target_include_directories(test_embed PRIVATE "${CATCH_INCLUDE_DIR}")
 pybind11_enable_warnings(test_embed)
 
-if(NOT CMAKE_VERSION VERSION_LESS 3.0)
-  target_link_libraries(test_embed PRIVATE pybind11::embed)
-else()
-  target_include_directories(test_embed PRIVATE "${PYBIND11_INCLUDE_DIR}" "${PYTHON_INCLUDE_DIRS}")
-  target_compile_options(test_embed PRIVATE "${PYBIND11_CPP_STANDARD}")
-  target_link_libraries(test_embed PRIVATE "${PYTHON_LIBRARIES}")
-endif()
+target_link_libraries(test_embed PRIVATE pybind11::embed)
 
 find_package(Threads REQUIRED)
-target_link_libraries(test_embed PUBLIC ${CMAKE_THREAD_LIBS_INIT})
+target_link_libraries(test_embed PUBLIC Threads::Threads)
 
-add_custom_target(cpptest COMMAND $<TARGET_FILE:test_embed>
+add_custom_target(cpptest COMMAND "$<TARGET_FILE:test_embed>"
                   WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
 
 pybind11_add_module(external_module THIN_LTO external_module.cpp)
@@ -43,13 +37,3 @@ endforeach()
 add_dependencies(cpptest external_module)
 
 add_dependencies(check cpptest)
-
-if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
-  if(CMAKE_CXX_STANDARD LESS 17)
-    target_compile_options(test_embed PUBLIC -Wno-deprecated-register)
-    target_compile_options(external_module PUBLIC -Wno-deprecated-register)
-  else()
-    target_compile_options(test_embed PUBLIC -Wno-register)
-    target_compile_options(external_module PUBLIC -Wno-register)
-  endif()
-endif()
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 58426887a5..8121aa6d7f 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -75,7 +75,6 @@ list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})
 
 include(pybind11Tools)
 
-if(NOT (CMAKE_VERSION VERSION_LESS 3.0))
 #-----------------------------------------------------------------------------
 # Don't include targets if this file is being picked up by another
 # project which has already built this as a subproject
@@ -85,20 +84,14 @@ if(NOT TARGET ${PN}::pybind11)
 
     find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} MODULE REQUIRED)
     set_property(TARGET ${PN}::pybind11 APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${PYTHON_INCLUDE_DIRS})
+    set_property(TARGET ${PN}::pybind11 APPEND PROPERTY INTERFACE_SYSTEM_INCLUDE_DIRECTORIES ${PYTHON_INCLUDE_DIRS})
     set_property(TARGET ${PN}::embed APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${PYTHON_LIBRARIES})
     if(WIN32 OR CYGWIN)
       set_property(TARGET ${PN}::module APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${PYTHON_LIBRARIES})
     endif()
 
-    if(CMAKE_VERSION VERSION_LESS 3.3)
-      set_property(TARGET ${PN}::pybind11 APPEND PROPERTY INTERFACE_COMPILE_OPTIONS "${PYBIND11_CPP_STANDARD}")
-    else()
-      set_property(TARGET ${PN}::pybind11 APPEND PROPERTY INTERFACE_COMPILE_OPTIONS $<$<COMPILE_LANGUAGE:CXX>:${PYBIND11_CPP_STANDARD}>)
-    endif()
-
     get_property(_iid TARGET ${PN}::pybind11 PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
     get_property(_ill TARGET ${PN}::module PROPERTY INTERFACE_LINK_LIBRARIES)
     set(${PN}_INCLUDE_DIRS ${_iid})
     set(${PN}_LIBRARIES ${_ico} ${_ill})
 endif()
-endif()
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index be536e6b6f..3a141dd600 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -5,56 +5,41 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 2.8.12)
+cmake_minimum_required(VERSION 3.7)
+
+# VERSION 3.7...3.18, but some versions of VS have a patched CMake 3.11
+# that do not work properly with this syntax, so using the following workaround:
+if(${CMAKE_VERSION} VERSION_LESS 3.18)
+    cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
+else()
+    cmake_policy(VERSION 3.18)
+endif()
 
 # Add a CMake parameter for choosing a desired Python version
 if(NOT PYBIND11_PYTHON_VERSION)
-  set(PYBIND11_PYTHON_VERSION "" CACHE STRING "Python version to use for compiling modules")
+    set(PYBIND11_PYTHON_VERSION "" CACHE STRING "Python version to use for compiling modules")
 endif()
 
-set(Python_ADDITIONAL_VERSIONS 3.9 3.8 3.7 3.6 3.5 3.4)
+# A user can set versions manually too
+set(Python_ADDITIONAL_VERSIONS "3.9;3.8;3.7;3.6;3.5;3.4" CACHE INTERNAL "")
 find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} REQUIRED)
 
 include(CheckCXXCompilerFlag)
 include(CMakeParseArguments)
 
 # Use the language standards abstraction if CMake supports it with the current compiler
-if(NOT CMAKE_VERSION VERSION_LESS 3.1)
-  if(NOT CMAKE_CXX_STANDARD)
-    if(CMAKE_CXX14_STANDARD_COMPILE_OPTION)
-      set(CMAKE_CXX_STANDARD 14)
-    elseif(CMAKE_CXX11_STANDARD_COMPILE_OPTION)
-      set(CMAKE_CXX_STANDARD 11)
+if(PYBIND11_CPP_STANDARD)
+    message(WARNING "USE -DCMAKE_CXX_STANDARD=11 instead of PYBIND11_PYTHON_VERSION")
+    if(NOT CMAKE_CXX_STANDARD)
+        string(REGEX MATCH
+            [=[..^]=]
+            VAL
+            "${PYBIND11_CPP_STANDARD}")
+        set(CMAKE_CXX_STANDARD ${VAL})
     endif()
-  endif()
-  if(CMAKE_CXX_STANDARD)
-    set(CMAKE_CXX_EXTENSIONS OFF)
-    set(CMAKE_CXX_STANDARD_REQUIRED ON)
-  endif()
 endif()
 
-# Fall back to heuristics
-if(NOT PYBIND11_CPP_STANDARD AND NOT CMAKE_CXX_STANDARD)
-  if(MSVC)
-    set(PYBIND11_CPP_STANDARD /std:c++14)
-  else()
-    check_cxx_compiler_flag("-std=c++14" HAS_CPP14_FLAG)
-    if(HAS_CPP14_FLAG)
-      set(PYBIND11_CPP_STANDARD -std=c++14)
-    else()
-      check_cxx_compiler_flag("-std=c++11" HAS_CPP11_FLAG)
-      if(HAS_CPP11_FLAG)
-        set(PYBIND11_CPP_STANDARD -std=c++11)
-      endif()
-    endif()
-  endif()
 
-  if(NOT PYBIND11_CPP_STANDARD)
-    message(FATAL_ERROR "Unsupported compiler -- pybind11 requires C++11 support!")
-  endif()
-  set(PYBIND11_CPP_STANDARD ${PYBIND11_CPP_STANDARD} CACHE STRING
-      "C++ standard flag, e.g. -std=c++11, -std=c++14, /std:c++14.  Defaults to C++14 mode." FORCE)
-endif()
 
 # Checks whether the given CXX/linker flags can compile and link a cxx file.  cxxflags and
 # linkerflags are lists of flags to use.  The result variable is a unique variable name for each set
@@ -117,16 +102,18 @@ function(_pybind11_add_lto_flags target_name prefer_thin_lto)
 
   # Enable LTO flags if found, except for Debug builds
   if (PYBIND11_LTO_CXX_FLAGS)
-    target_compile_options(${target_name} PRIVATE "$<$<NOT:$<CONFIG:Debug>>:${PYBIND11_LTO_CXX_FLAGS}>")
+    set(not_debug "$<NOT:$<CONFIG:Debug>>")
+    set(cxx_lang "$<COMPILE_LANGUAGE:CXX>")
+    target_compile_options(${target_name} PRIVATE "$<$<AND:${not_debug},${cxx_lang}>:${PYBIND11_LTO_CXX_FLAGS}>")
   endif()
   if (PYBIND11_LTO_LINKER_FLAGS)
-    target_link_libraries(${target_name} PRIVATE "$<$<NOT:$<CONFIG:Debug>>:${PYBIND11_LTO_LINKER_FLAGS}>")
+    target_link_libraries(${target_name} PRIVATE "$<${not_debug}:${PYBIND11_LTO_LINKER_FLAGS}>")
   endif()
 endfunction()
 
 # Build a Python extension module:
 # pybind11_add_module(<name> [MODULE | SHARED] [EXCLUDE_FROM_ALL]
-#                     [NO_EXTRAS] [SYSTEM] [THIN_LTO] source1 [source2 ...])
+#                     [NO_EXTRAS] [THIN_LTO] source1 [source2 ...])
 #
 function(pybind11_add_module target_name)
   set(options MODULE SHARED EXCLUDE_FROM_ALL NO_EXTRAS SYSTEM THIN_LTO)
@@ -148,29 +135,13 @@ function(pybind11_add_module target_name)
 
   add_library(${target_name} ${lib_type} ${exclude_from_all} ${ARG_UNPARSED_ARGUMENTS})
 
-  if(ARG_SYSTEM)
-    set(inc_isystem SYSTEM)
-  else()
-    set(inc_isystem "")
-  endif()
+  target_link_libraries(${target_name} PRIVATE pybind11::module)
 
-  set(PYBIND11_INCLUDE_DIR_SELECTED "")
-  if(PYBIND11_INCLUDE_DIR)
-    # from project CMakeLists.txt
-    set(PYBIND11_INCLUDE_DIR_SELECTED ${PYBIND11_INCLUDE_DIR})
-  elseif(pybind11_INCLUDE_DIR)
-    # from pybind11Config
-    set(PYBIND11_INCLUDE_DIR_SELECTED ${pybind11_INCLUDE_DIR})
-  else()
-    message(FATAL "No pybind11_INCLUDE_DIR available. Use "
-      "find_package(pybind11) before calling pybind11_add_module.")
+  if(ARG_SYSTEM)
+      message(STATUS "Warning: this does not have an effect - use NO_SYSTEM_FROM_IMPORTED if using imported targets")
   endif()
 
-  target_include_directories(${target_name} ${inc_isystem}
-    PRIVATE ${PYBIND11_INCLUDE_DIR_SELECTED}
-    PRIVATE ${PYTHON_INCLUDE_DIRS})
-
-  # Python debug libraries expose slightly different objects
+  # Python debug libraries expose slightly different objects before 3.8
   # https://docs.python.org/3.6/c-api/intro.html#debugging-builds
   # https://stackoverflow.com/questions/39161202/how-to-work-around-missing-pymodule-create2-in-amd64-win-python35-d-lib
   if(PYTHON_IS_DEBUG)
@@ -189,54 +160,25 @@ function(pybind11_add_module target_name)
   set_target_properties(${target_name} PROPERTIES CXX_VISIBILITY_PRESET "hidden")
   set_target_properties(${target_name} PROPERTIES CUDA_VISIBILITY_PRESET "hidden")
 
-  if(WIN32 OR CYGWIN)
-    # Link against the Python shared library on Windows
-    target_link_libraries(${target_name} PRIVATE ${PYTHON_LIBRARIES})
-  elseif(APPLE)
-    # It's quite common to have multiple copies of the same Python version
-    # installed on one's system. E.g.: one copy from the OS and another copy
-    # that's statically linked into an application like Blender or Maya.
-    # If we link our plugin library against the OS Python here and import it
-    # into Blender or Maya later on, this will cause segfaults when multiple
-    # conflicting Python instances are active at the same time (even when they
-    # are of the same version).
-
-    # Windows is not affected by this issue since it handles DLL imports
-    # differently. The solution for Linux and Mac OS is simple: we just don't
-    # link against the Python library. The resulting shared library will have
-    # missing symbols, but that's perfectly fine -- they will be resolved at
-    # import time.
-
-    target_link_libraries(${target_name} PRIVATE "-undefined dynamic_lookup")
-
-    if(ARG_SHARED)
-      # Suppress CMake >= 3.0 warning for shared libraries
-      set_target_properties(${target_name} PROPERTIES MACOSX_RPATH ON)
-    endif()
-  endif()
-
-  # Make sure C++11/14 are enabled
-  if(PYBIND11_CPP_STANDARD)
-    if(CMAKE_VERSION VERSION_LESS 3.3)
-      target_compile_options(${target_name} PUBLIC ${PYBIND11_CPP_STANDARD})
-    else()
-      target_compile_options(${target_name} PUBLIC $<$<COMPILE_LANGUAGE:CXX>:${PYBIND11_CPP_STANDARD}>)
-    endif()
-  endif()
-
-  # Python 2 doesn't really support C++17, Clang warns/errors over it
-  if(CMAKE_CXX_STANDARD
-     AND CMAKE_CXX_COMPILER_ID MATCHES "Clang"
-     AND PYTHON_VERSION VERSION_LESS 3.0
-     AND NOT CMAKE_CXX_STANDARD LESS 17)
-       target_compile_options(${target_name} PUBLIC -Wno-register)
-  endif()
 
   if(ARG_NO_EXTRAS)
-    return()
+      return()
   endif()
 
-  _pybind11_add_lto_flags(${target_name} ${ARG_THIN_LTO})
+  if(CMAKE_VERSION VERSION_LESS 3.9 OR PYBIND11_CLASSIC_LTO)
+      _pybind11_add_lto_flags(${target_name} ${ARG_THIN_LTO})
+  else()
+      include(CheckIPOSupported)
+      check_ipo_supported(RESULT supported OUTPUT error)
+      if(supported)
+          set_property(
+            TARGET
+              ${target_name}
+            PROPERTY
+              INTERPROCEDURAL_OPTIMIZATION TRUE
+            )
+      endif()
+  endif()
 
   if (NOT MSVC AND NOT ${CMAKE_BUILD_TYPE} MATCHES Debug|RelWithDebInfo)
     # Strip unnecessary sections of the binary on Linux/Mac OS

From 1b92cd17034df657de2a677f5182946ca646dd6e Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 29 Jul 2020 15:02:53 -0400
Subject: [PATCH 61/73] fix: address review points from @YannickJadoul

---
 .appveyor.yml                 |  2 +-
 docs/compiling.rst            | 25 +++++++++++++++-------
 tools/pybind11Config.cmake.in | 39 +++++++++++++++++------------------
 tools/pybind11Tools.cmake     | 11 +++++++---
 4 files changed, 46 insertions(+), 31 deletions(-)

diff --git a/.appveyor.yml b/.appveyor.yml
index fbcf8a3784..b33a4ccf4e 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -26,7 +26,7 @@ install:
     $env:CMAKE_INCLUDE_PATH = "eigen-eigen-67e894c6cd8f;$env:CMAKE_INCLUDE_PATH"
 build_script:
 - cmake -G "%CMAKE_GENERATOR%" -A "%CMAKE_ARCH%"
-    -DPYBIND11_CPP_STANDARD=/std:c++14
+    -DCMAKE_CXX_STANDARD=14
     -DPYBIND11_WERROR=ON
     -DDOWNLOAD_CATCH=ON
     -DCMAKE_SUPPRESS_REGENERATION=1
diff --git a/docs/compiling.rst b/docs/compiling.rst
index dce44c8791..cef0d5942f 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -103,9 +103,9 @@ standard explicitly with
 
 .. code-block:: cmake
 
-    # Use just one of these:
-    set(CMAKE_CXX_STANDARD 14)
-    set(CMAKE_CXX_STANDARD 17)
+    set(CMAKE_CXX_STANDARD 14)  # or 11, 14, 17, 20
+    set(CMAKE_CXX_STANDARD_REQUIRED ON)  # optional, ensure standard is supported
+    set(CMAKE_CXX_EXTENSIONS OFF)  # optional, keep compiler extensionsn off
 
 
 The variables can also be set when calling CMake from the command line using
@@ -120,7 +120,11 @@ For example:
 .. code-block:: bash
 
     cmake -DPYBIND11_PYTHON_VERSION=3.6 ..
-    # or
+
+    # Another method:
+    cmake -DPYTHON_EXECUTABLE=/path/to/python ..
+
+    # You will often see this idiom:
     cmake -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") ..
 
 find_package vs. add_subdirectory
@@ -144,12 +148,19 @@ the pybind11 repository  :
 
 .. code-block:: bash
 
+    # Classic CMake
     cd pybind11
     mkdir build
     cd build
     cmake ..
     make install
 
+    # CMake 3.15+
+    cd pybind11
+    cmake -S . -B build
+    cmake --build build -j 2  # Build on 2 cores
+    cmake --install build
+
 Once detected, the aforementioned ``pybind11_add_module`` can be employed as
 before. The function usage and configuration variables are identical no matter
 if pybind11 is added as a subdirectory or found as an installed package. You
@@ -198,11 +209,11 @@ to an independently constructed (through ``add_library``, not
 
     .. code-block:: cmake
 
-        cmake_minimum_required(3.9)
         set(CMAKE_CXX_VISIBILITY_PRESET hidden)
-        set(CMAKE_INTERPROCEDURAL_OPTIMIZATION ON)
+        set(CMAKE_VISIBILITY_INLINES_HIDDEN ON)
+        set(CMAKE_INTERPROCEDURAL_OPTIMIZATION ON)  # CMake 3.9+ required
 
-    or set teh corisponding property (without the ``CMAKE_``) on the targets
+    or set the corresponding property (without the ``CMAKE_``) on the targets
     manually.
 
 Embedding the Python interpreter
diff --git a/tools/pybind11Config.cmake.in b/tools/pybind11Config.cmake.in
index 8121aa6d7f..bcc74d6bfb 100644
--- a/tools/pybind11Config.cmake.in
+++ b/tools/pybind11Config.cmake.in
@@ -60,17 +60,15 @@
 
 @PACKAGE_INIT@
 
-set(PN pybind11)
+# Location of pybind11/pybind11.h
+set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/@CMAKE_INSTALL_INCLUDEDIR@")
 
-# location of pybind11/pybind11.h
-set(${PN}_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/@CMAKE_INSTALL_INCLUDEDIR@")
+set(pybind11_LIBRARY "")
+set(pybind11_DEFINITIONS USING_pybind11)
 
-set(${PN}_LIBRARY "")
-set(${PN}_DEFINITIONS USING_${PN})
+check_required_components(pybind11)
 
-check_required_components(${PN})
-
-# make detectable the FindPythonLibsNew.cmake module
+# Make the FindPythonLibsNew.cmake module available
 list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})
 
 include(pybind11Tools)
@@ -79,19 +77,20 @@ include(pybind11Tools)
 # Don't include targets if this file is being picked up by another
 # project which has already built this as a subproject
 #-----------------------------------------------------------------------------
-if(NOT TARGET ${PN}::pybind11)
-    include("${CMAKE_CURRENT_LIST_DIR}/${PN}Targets.cmake")
+if(NOT TARGET pybind11::pybind11)
+    include("${CMAKE_CURRENT_LIST_DIR}/pybind11Targets.cmake")
 
     find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} MODULE REQUIRED)
-    set_property(TARGET ${PN}::pybind11 APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${PYTHON_INCLUDE_DIRS})
-    set_property(TARGET ${PN}::pybind11 APPEND PROPERTY INTERFACE_SYSTEM_INCLUDE_DIRECTORIES ${PYTHON_INCLUDE_DIRS})
-    set_property(TARGET ${PN}::embed APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${PYTHON_LIBRARIES})
-    if(WIN32 OR CYGWIN)
-      set_property(TARGET ${PN}::module APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${PYTHON_LIBRARIES})
-    endif()
 
-    get_property(_iid TARGET ${PN}::pybind11 PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
-    get_property(_ill TARGET ${PN}::module PROPERTY INTERFACE_LINK_LIBRARIES)
-    set(${PN}_INCLUDE_DIRS ${_iid})
-    set(${PN}_LIBRARIES ${_ico} ${_ill})
+    set_property(TARGET pybind11::pybind11 APPEND PROPERTY INTERFACE_INCLUDE_DIRECTORIES ${PYTHON_INCLUDE_DIRS})
+    set_property(TARGET pybind11::pybind11 APPEND PROPERTY INTERFACE_SYSTEM_INCLUDE_DIRECTORIES ${PYTHON_INCLUDE_DIRS})
+
+    set_property(TARGET pybind11::embed APPEND PROPERTY INTERFACE_LINK_LIBRARIES ${PYTHON_LIBRARIES})
+    set_property(TARGET pybind11::module APPEND PROPERTY INTERFACE_LINK_LIBRARIES
+        "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>")
+
+    get_property(_iid TARGET pybind11::pybind11 PROPERTY INTERFACE_INCLUDE_DIRECTORIES)
+    get_property(_ill TARGET pybind11::module PROPERTY INTERFACE_LINK_LIBRARIES)
+    set(pybind11_INCLUDE_DIRS ${_iid})
+    set(pybind11_LIBRARIES ${_ico} ${_ill})
 endif()
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 3a141dd600..742699aca7 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -27,15 +27,20 @@ find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} REQUIRED)
 include(CheckCXXCompilerFlag)
 include(CMakeParseArguments)
 
-# Use the language standards abstraction if CMake supports it with the current compiler
+# Warn or error if old variable name used
 if(PYBIND11_CPP_STANDARD)
-    message(WARNING "USE -DCMAKE_CXX_STANDARD=11 instead of PYBIND11_PYTHON_VERSION")
     if(NOT CMAKE_CXX_STANDARD)
         string(REGEX MATCH
             [=[..^]=]
             VAL
             "${PYBIND11_CPP_STANDARD}")
-        set(CMAKE_CXX_STANDARD ${VAL})
+        set(supported_standards 11 14 17 20)
+        if("${VAL}" IN_LIST supported_standards)
+            message(WARNING "USE -DCMAKE_CXX_STANDARD=${VAL} instead of PYBIND11_PYTHON_VERSION")
+            set(CMAKE_CXX_STANDARD ${VAL})
+        else()
+            message(FATAL_ERROR "PYBIND11_CPP_STANDARD should be replaced with CMAKE_CXX_STANDARD")
+        endif()
     endif()
 endif()
 

From f64d5aa6da17ef92987a0b740f94c5d8cbce3229 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 29 Jul 2020 20:10:38 -0400
Subject: [PATCH 62/73] fix: typo for warning on C++17, support Win + 2.7

---
 .github/workflows/ci.yml | 4 ++--
 CMakeLists.txt           | 7 ++++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bf0879db1f..b51b0c6303 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -118,14 +118,14 @@ jobs:
       shell: bash
       run: >
         cmake -S . -B build2
-        -DPYBIND17_WERROR=ON
+        -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.max-cxx-std }}
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
 
     - name: Build C++${{ matrix.max-cxx-std }}
-      run: cmake --build build2 -j 2
+      run: cmake --build build2 -j 2 -v
 
     - name: Python tests C++${{ matrix.max-cxx-std }}
       run: cmake --build build2 --target pytest
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2227559da3..0337f0b034 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -176,9 +176,14 @@ endif()
 
 message(STATUS "CXX Compiler version: ${CMAKE_CXX_COMPILER_VERSION}")
 
+# Workaround for Python 2.7 and C++17 (C++14 as a warning) incompatibility
 set(clang_4plus "$<AND:$<CXX_COMPILER_ID:Clang>,$<NOT:$<VERSION_LESS:$<CXX_COMPILER_VERSION>,3.9>>>")
 set(no_register "$<OR:${clang_4plus},$<CXX_COMPILER_ID:AppleClang>>")
-target_compile_options(pybind11 INTERFACE "$<${no_register}:-Wno-register;-Wno-deprecated-register>")
+set(cxx_no_register "$<AND:$<COMPILE_LANGUAGE:CXX>,${no_register}>")
+set(msvc "$<CXX_COMPILER_ID:MSVC>")
+target_compile_options(
+  pybind11 INTERFACE "$<${cxx_no_register}:-Wno-register;-Wno-deprecated-register>"
+                     "$<${msvc}:/wd5033>")
 
 add_library(embed INTERFACE)
 add_library(pybind11::embed ALIAS embed)

From 1651c324928cc849bcd1cefdf74076574a4db868 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 30 Jul 2020 16:04:26 -0400
Subject: [PATCH 63/73] update: address review points

---
 .github/workflows/ci.yml         |  6 ++---
 CMakeLists.txt                   | 39 +++++++++++++++++++-------------
 docs/compiling.rst               |  4 ++--
 include/pybind11/detail/common.h |  3 +--
 4 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b51b0c6303..fc9d04c924 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -106,10 +106,10 @@ jobs:
       run: cmake --build build -j 2
 
     - name: Python tests C++11
-      run: cmake --build build --target pytest -j 2 -v
+      run: cmake --build build --target pytest -j 2
 
     - name: C++11 tests
-      run: cmake --build build --target cpptest -j 2 -v
+      run: cmake --build build --target cpptest -j 2
 
     - name: Interface test C++11
       run: cmake --build build --target test_cmake_build
@@ -125,7 +125,7 @@ jobs:
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
 
     - name: Build C++${{ matrix.max-cxx-std }}
-      run: cmake --build build2 -j 2 -v
+      run: cmake --build build2 -j 2
 
     - name: Python tests C++${{ matrix.max-cxx-std }}
       run: cmake --build build2 --target pytest
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0337f0b034..d5a39b4d76 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,7 +7,7 @@
 
 cmake_minimum_required(VERSION 3.7)
 
-# VERSION 3.7...3.18, but some versions of VS have a patched CMake 3.11
+# VERSION 3.7...3.18, but some versions of MCVS have a patched CMake 3.11
 # that do not work properly with this syntax, so using the following workaround:
 if(${CMAKE_VERSION} VERSION_LESS 3.18)
     cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
@@ -21,14 +21,19 @@ file(
     "${CMAKE_CURRENT_SOURCE_DIR}/include/pybind11/detail/common.h"
   pybind11_version_defines
   REGEX
-    "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH|TYPE) ")
+    "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) ")
 
 foreach(ver ${pybind11_version_defines})
-    if (ver MATCHES [=[#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH|TYPE) +"?([^ ^"]+)"?$]=])
+    if (ver MATCHES [[#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) +([^ ]+)$]])
         set(PYBIND11_VERSION_${CMAKE_MATCH_1} "${CMAKE_MATCH_2}")
     endif()
 endforeach()
 
+if(PYBIND11_VERSION_PATCH MATCHES [[([a-zA-Z]+)]])
+    set(PYBIND11_VERSION_TYPE "${CMAKE_MATCH_1}")
+endif()
+string(REGEX MATCH "[0-9]+" PYBIND11_VERSION_PATCH "${PYBIND11_VERSION_PATCH}")
+
 project(
     pybind11
   LANGUAGES
@@ -42,10 +47,11 @@ include(GNUInstallDirs)
 include(CMakePackageConfigHelpers)
 include(CMakeDependentOption)
 
+message(STATUS "pybind11 v${pybind11_VERSION} ${PYBIND11_VERSION_TYPE}")
+
 # Check if pybind11 is being used directly or via add_subdirectory
 if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
     set(PYBIND11_MASTER_PROJECT ON)
-    message(STATUS "pybind11 v${pybind11_VERSION} ${PYBIND11_VERSION_TYPE}")
     message(STATUS "CMake ${CMAKE_VERSION}")
 
     if(CMAKE_CXX_STANDARD)
@@ -92,6 +98,9 @@ set(PYBIND11_HEADERS
     include/pybind11/stl.h
     include/pybind11/stl_bind.h
 )
+
+# TODO: compare with grep and warn if missmatched
+
 # cmake 3.12 added list(TRANSFORM <list> PREPEND
 # But we can't use it yet
 string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/"
@@ -125,6 +134,7 @@ endif()
 
 # Note: when creating targets, you cannot use if statements at configure time -
 # you need generator expressions, because those will be placed in the target file.
+# You can also place ifs *in* the Config.in, but not here.
 
 # Build an interface library target:
 add_library(pybind11 INTERFACE)
@@ -139,21 +149,14 @@ if(CMAKE_VERSION VERSION_LESS 3.13)
     target_compile_features(
         pybind11
       INTERFACE
-        cxx_auto_type
-        cxx_constexpr
-        cxx_defaulted_functions
-        cxx_lambdas
-        cxx_nullptr
-        cxx_range_for
-        cxx_right_angle_brackets
-        cxx_strong_enums
+        cxx_inheriting_constructors
         cxx_user_literals
-        cxx_variadic_templates
+        cxx_right_angle_brackets
       )
 else()
     # This was added in CMake 3.8, but we are keeping a consistent breaking
     # point for the config file at 3.13. A config generated by CMake 3.13+
-    # can ony be read in 3.13+ due to the SHELL usage later, so this is safe to do.
+    # can only be read in 3.13+ due to the SHELL usage later, so this is safe to do.
     target_compile_features(pybind11 INTERFACE cxx_std_11)
 endif()
 
@@ -170,13 +173,16 @@ if(CMAKE_VERSION VERSION_LESS 3.13)
     target_link_libraries(module INTERFACE "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
 else()
     # SHELL (3.12+) forces this to remain together, and link_options was added in 3.13+
+    # This is safer, because you are ensured the deduplication pass in CMake will not consider
+    # these separate and remove one but not the other.
     target_link_options(module INTERFACE "$<$<PLATFORM_ID:Darwin>:SHELL:-undefined dynamic_lookup>")
 endif()
 
 
-message(STATUS "CXX Compiler version: ${CMAKE_CXX_COMPILER_VERSION}")
-
 # Workaround for Python 2.7 and C++17 (C++14 as a warning) incompatibility
+# This adds the flags -Wno-register and -Wno-deprecated-register if the compiler
+# is Clang 3.9+ or AppleClang and the compile language is CXX, or /wd5033 for MSVC (all languages,
+# since MSVC didn't recognize COMPILE_LANGUAGE until CMake 3.11+).
 set(clang_4plus "$<AND:$<CXX_COMPILER_ID:Clang>,$<NOT:$<VERSION_LESS:$<CXX_COMPILER_VERSION>,3.9>>>")
 set(no_register "$<OR:${clang_4plus},$<CXX_COMPILER_ID:AppleClang>>")
 set(cxx_no_register "$<AND:$<COMPILE_LANGUAGE:CXX>,${no_register}>")
@@ -214,6 +220,7 @@ if(PYBIND11_INSTALL)
 
         set(CMAKE_SIZEOF_VOID_P ${_PYBIND11_CMAKE_SIZEOF_VOID_P})
     else()
+        # CMake 3.14+ natively supports header-only libraries
         write_basic_package_version_file(
             ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
           VERSION
diff --git a/docs/compiling.rst b/docs/compiling.rst
index cef0d5942f..07f93e7cc5 100644
--- a/docs/compiling.rst
+++ b/docs/compiling.rst
@@ -97,7 +97,7 @@ Configuration variables
 -----------------------
 
 By default, pybind11 will compile modules with the compiler default or the
-minimum standard required by PyBind11, whichever is higher.  You can set the
+minimum standard required by pybind11, whichever is higher.  You can set the
 standard explicitly with
 `CMAKE_CXX_STANDARD <https://cmake.org/cmake/help/latest/variable/CMAKE_CXX_STANDARD.html>`_:
 
@@ -124,7 +124,7 @@ For example:
     # Another method:
     cmake -DPYTHON_EXECUTABLE=/path/to/python ..
 
-    # You will often see this idiom:
+    # This often is a good way to get the current Python, works in environments:
     cmake -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") ..
 
 find_package vs. add_subdirectory
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
index 2d83e482df..8923faef76 100644
--- a/include/pybind11/detail/common.h
+++ b/include/pybind11/detail/common.h
@@ -11,8 +11,7 @@
 
 #define PYBIND11_VERSION_MAJOR 2
 #define PYBIND11_VERSION_MINOR 6
-#define PYBIND11_VERSION_PATCH 0
-#define PYBIND11_VERSION_TYPE "dev"
+#define PYBIND11_VERSION_PATCH dev0
 
 #define PYBIND11_NAMESPACE_BEGIN(name) namespace name {
 #define PYBIND11_NAMESPACE_END(name) }

From e2a96890e12e71074ed3ff4acfd23b83fc14f923 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Wed, 29 Jul 2020 16:42:07 -0400
Subject: [PATCH 64/73] format: add cmake-format to pre-commit

---
 .cmake-format.yaml      | 69 +++++++++++++++++++++++++++++++++++++++++
 .pre-commit-config.yaml |  6 ++++
 tests/CMakeLists.txt    |  2 +-
 3 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 .cmake-format.yaml

diff --git a/.cmake-format.yaml b/.cmake-format.yaml
new file mode 100644
index 0000000000..fc69b40a01
--- /dev/null
+++ b/.cmake-format.yaml
@@ -0,0 +1,69 @@
+parse:
+  additional_commands:
+    pybind11_add_module:
+      flags:
+        - THIN_LTO
+        - MODULE
+        - SHARED
+        - NO_EXTRAS
+        - EXCLUDE_FROM_ALL
+        - SYSTEM
+
+format:
+  line_width: 99
+  tab_size: 2
+
+  # If an argument group contains more than this many sub-groups
+  # (parg or kwarg groups) then force it to a vertical layout.
+  max_subgroups_hwrap: 2
+
+  # If a positional argument group contains more than this many
+  # arguments, then force it to a vertical layout.
+  max_pargs_hwrap: 6
+
+  # If a cmdline positional group consumes more than this many
+  # lines without nesting, then invalidate the layout (and nest)
+  max_rows_cmdline: 2
+  separate_ctrl_name_with_space: false
+  separate_fn_name_with_space: false
+  dangle_parens: false
+
+  # If the trailing parenthesis must be 'dangled' on its on
+  # 'line, then align it to this reference: `prefix`: the start'
+  # 'of the statement,  `prefix-indent`: the start of the'
+  # 'statement, plus one indentation  level, `child`: align to'
+  # the column of the arguments
+  dangle_align: prefix
+  # If the statement spelling length (including space and
+  # parenthesis) is smaller than this amount, then force reject
+  # nested layouts.
+  min_prefix_chars: 4
+
+  # If the statement spelling length (including space and
+  # parenthesis) is larger than the tab width by more than this
+  # amount, then force reject un-nested layouts.
+  max_prefix_chars: 10
+
+  # If a candidate layout is wrapped horizontally but it exceeds
+  # this many lines, then reject the layout.
+  max_lines_hwrap: 2
+
+  line_ending: unix
+
+  # Format command names consistently as 'lower' or 'upper' case
+  command_case: canonical
+
+  # Format keywords consistently as 'lower' or 'upper' case
+  # unchanged is valid too
+  keyword_case: 'upper'
+
+  # A list of command names which should always be wrapped
+  always_wrap: []
+
+  # If true, the argument lists which are known to be sortable
+  # will be sorted lexicographically
+  enable_sort: true
+
+  # If true, the parsers may infer whether or not an argument
+  # list is sortable (without annotation).
+  autosort: false
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 3e68d34f07..7fb3a13b70 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -26,6 +26,12 @@ repos:
     additional_dependencies: [flake8-bugbear, pep8-naming]
     exclude: ^(docs/.*|tools/.*)$
 
+- repo: https://github.com/cheshirekow/cmake-format-precommit
+  rev: v0.6.10
+  hooks:
+  - id: cmake-format
+    additional_dependencies: [pyyaml]
+
 - repo: local
   hooks:
   - id: check-style
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 37a8b81b81..cab273bc1d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -217,7 +217,7 @@ endforeach()
 set(testdir ${CMAKE_CURRENT_SOURCE_DIR})
 foreach(target ${test_targets})
   set(test_files ${PYBIND11_TEST_FILES})
-  if(NOT target STREQUAL "pybind11_tests")
+  if(NOT "${target}" STREQUAL "pybind11_tests")
     set(test_files "")
   endif()
 

From 94db5c5ed1a0f8bde74e8b31e603c7bcccf6e3f6 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henryschreineriii@gmail.com>
Date: Thu, 30 Jul 2020 16:20:10 -0400
Subject: [PATCH 65/73] format: apply cmake-format

---
 .cmake-format.yaml                            |   4 +
 CMakeLists.txt                                | 241 +++++++++---------
 tests/CMakeLists.txt                          | 178 +++++++------
 tests/test_cmake_build/CMakeLists.txt         |  43 ++--
 .../installed_embed/CMakeLists.txt            |   1 -
 .../installed_function/CMakeLists.txt         |  11 +-
 .../installed_target/CMakeLists.txt           |  11 +-
 .../subdirectory_embed/CMakeLists.txt         |  18 +-
 .../subdirectory_function/CMakeLists.txt      |  11 +-
 .../subdirectory_target/CMakeLists.txt        |  11 +-
 tests/test_embed/CMakeLists.txt               |  19 +-
 tools/FindCatch.cmake                         |  18 +-
 tools/FindEigen3.cmake                        |  27 +-
 tools/FindPythonLibsNew.cmake                 | 170 ++++++------
 tools/pybind11Tools.cmake                     | 135 +++++-----
 15 files changed, 484 insertions(+), 414 deletions(-)

diff --git a/.cmake-format.yaml b/.cmake-format.yaml
index fc69b40a01..a2a69f3f89 100644
--- a/.cmake-format.yaml
+++ b/.cmake-format.yaml
@@ -67,3 +67,7 @@ format:
   # If true, the parsers may infer whether or not an argument
   # list is sortable (without annotation).
   autosort: false
+
+# Causes a few issues - can be solved later, possibly.
+markup:
+  enable_markup: false
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d5a39b4d76..31e253f9dd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,37 +10,30 @@ cmake_minimum_required(VERSION 3.7)
 # VERSION 3.7...3.18, but some versions of MCVS have a patched CMake 3.11
 # that do not work properly with this syntax, so using the following workaround:
 if(${CMAKE_VERSION} VERSION_LESS 3.18)
-    cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
+  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-    cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.18)
 endif()
 
 # Extract project version from source
-file(
-  STRINGS
-    "${CMAKE_CURRENT_SOURCE_DIR}/include/pybind11/detail/common.h"
-  pybind11_version_defines
-  REGEX
-    "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) ")
+file(STRINGS "${CMAKE_CURRENT_SOURCE_DIR}/include/pybind11/detail/common.h"
+     pybind11_version_defines REGEX "#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) ")
 
 foreach(ver ${pybind11_version_defines})
-    if (ver MATCHES [[#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) +([^ ]+)$]])
-        set(PYBIND11_VERSION_${CMAKE_MATCH_1} "${CMAKE_MATCH_2}")
-    endif()
+  if(ver MATCHES [[#define PYBIND11_VERSION_(MAJOR|MINOR|PATCH) +([^ ]+)$]])
+    set(PYBIND11_VERSION_${CMAKE_MATCH_1} "${CMAKE_MATCH_2}")
+  endif()
 endforeach()
 
 if(PYBIND11_VERSION_PATCH MATCHES [[([a-zA-Z]+)]])
-    set(PYBIND11_VERSION_TYPE "${CMAKE_MATCH_1}")
+  set(PYBIND11_VERSION_TYPE "${CMAKE_MATCH_1}")
 endif()
 string(REGEX MATCH "[0-9]+" PYBIND11_VERSION_PATCH "${PYBIND11_VERSION_PATCH}")
 
 project(
-    pybind11
-  LANGUAGES
-    CXX
-  VERSION
-    "${PYBIND11_VERSION_MAJOR}.${PYBIND11_VERSION_MINOR}.${PYBIND11_VERSION_PATCH}"
-)
+  pybind11
+  LANGUAGES CXX
+  VERSION "${PYBIND11_VERSION_MAJOR}.${PYBIND11_VERSION_MINOR}.${PYBIND11_VERSION_PATCH}")
 
 # Standard includes
 include(GNUInstallDirs)
@@ -51,26 +44,25 @@ message(STATUS "pybind11 v${pybind11_VERSION} ${PYBIND11_VERSION_TYPE}")
 
 # Check if pybind11 is being used directly or via add_subdirectory
 if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
-    set(PYBIND11_MASTER_PROJECT ON)
-    message(STATUS "CMake ${CMAKE_VERSION}")
+  set(PYBIND11_MASTER_PROJECT ON)
+  message(STATUS "CMake ${CMAKE_VERSION}")
 
-    if(CMAKE_CXX_STANDARD)
-        set(CMAKE_CXX_EXTENSIONS OFF)
-        set(CMAKE_CXX_STANDARD_REQUIRED ON)
-    endif()
+  if(CMAKE_CXX_STANDARD)
+    set(CMAKE_CXX_EXTENSIONS OFF)
+    set(CMAKE_CXX_STANDARD_REQUIRED ON)
+  endif()
 else()
-    set(PYBIND11_MASTER_PROJECT OFF)
-    set(pybind11_system SYSTEM)
+  set(PYBIND11_MASTER_PROJECT OFF)
+  set(pybind11_system SYSTEM)
 endif()
 
 option(PYBIND11_INSTALL "Install pybind11 header files?" ${PYBIND11_MASTER_PROJECT})
 option(PYBIND11_TEST "Build pybind11 test suite?" ${PYBIND11_MASTER_PROJECT})
 option(PYBIND11_CLASSIC_LTO "Use the classic LTO flag algorithm, even on CMake 3.9+" OFF)
 cmake_dependent_option(
-    USE_PYTHON_INCLUDE_DIR
-    "Install pybind11 headers in Python include directory instead of default installation prefix" OFF
-    "PYBIND11_INSTALL" OFF
-)
+  USE_PYTHON_INCLUDE_DIR
+  "Install pybind11 headers in Python include directory instead of default installation prefix"
+  OFF "PYBIND11_INSTALL" OFF)
 
 # NB: when adding a header don't forget to also add it to setup.py
 set(PYBIND11_HEADERS
@@ -96,16 +88,14 @@ set(PYBIND11_HEADERS
     include/pybind11/pybind11.h
     include/pybind11/pytypes.h
     include/pybind11/stl.h
-    include/pybind11/stl_bind.h
-)
+    include/pybind11/stl_bind.h)
 
 # TODO: compare with grep and warn if missmatched
 
 # cmake 3.12 added list(TRANSFORM <list> PREPEND
 # But we can't use it yet
-string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/"
-       PYBIND11_HEADERS "${PYBIND11_HEADERS}")
-
+string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/" PYBIND11_HEADERS
+               "${PYBIND11_HEADERS}")
 
 # Classic mode
 
@@ -113,23 +103,37 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/tools")
 include(pybind11Tools)
 
 # Cache variables so pybind11_add_module can be used in parent projects
-set(PYBIND11_INCLUDE_DIR "${CMAKE_CURRENT_LIST_DIR}/include" CACHE INTERNAL "")
-set(PYTHON_INCLUDE_DIRS ${PYTHON_INCLUDE_DIRS} CACHE INTERNAL "")
-set(PYTHON_LIBRARIES ${PYTHON_LIBRARIES} CACHE INTERNAL "")
-set(PYTHON_MODULE_PREFIX ${PYTHON_MODULE_PREFIX} CACHE INTERNAL "")
-set(PYTHON_MODULE_EXTENSION ${PYTHON_MODULE_EXTENSION} CACHE INTERNAL "")
-set(PYTHON_VERSION_MAJOR ${PYTHON_VERSION_MAJOR} CACHE INTERNAL "")
-set(PYTHON_VERSION_MINOR ${PYTHON_VERSION_MINOR} CACHE INTERNAL "")
-set(PYTHON_IS_DEBUG "${PYTHON_IS_DEBUG}" CACHE INTERNAL "")
-
+set(PYBIND11_INCLUDE_DIR
+    "${CMAKE_CURRENT_LIST_DIR}/include"
+    CACHE INTERNAL "")
+set(PYTHON_INCLUDE_DIRS
+    ${PYTHON_INCLUDE_DIRS}
+    CACHE INTERNAL "")
+set(PYTHON_LIBRARIES
+    ${PYTHON_LIBRARIES}
+    CACHE INTERNAL "")
+set(PYTHON_MODULE_PREFIX
+    ${PYTHON_MODULE_PREFIX}
+    CACHE INTERNAL "")
+set(PYTHON_MODULE_EXTENSION
+    ${PYTHON_MODULE_EXTENSION}
+    CACHE INTERNAL "")
+set(PYTHON_VERSION_MAJOR
+    ${PYTHON_VERSION_MAJOR}
+    CACHE INTERNAL "")
+set(PYTHON_VERSION_MINOR
+    ${PYTHON_VERSION_MINOR}
+    CACHE INTERNAL "")
+set(PYTHON_IS_DEBUG
+    "${PYTHON_IS_DEBUG}"
+    CACHE INTERNAL "")
 
 if(PYBIND11_TEST OR (BUILD_TESTING AND PYBIND11_MASTER_PROJECT))
-    add_subdirectory(tests)
+  add_subdirectory(tests)
 endif()
 
-
 if(USE_PYTHON_INCLUDE_DIR)
-    file(RELATIVE_PATH CMAKE_INSTALL_INCLUDEDIR ${CMAKE_INSTALL_PREFIX} ${PYTHON_INCLUDE_DIRS})
+  file(RELATIVE_PATH CMAKE_INSTALL_INCLUDEDIR ${CMAKE_INSTALL_PREFIX} ${PYTHON_INCLUDE_DIRS})
 endif()
 
 # Note: when creating targets, you cannot use if statements at configure time -
@@ -138,26 +142,22 @@ endif()
 
 # Build an interface library target:
 add_library(pybind11 INTERFACE)
-add_library(pybind11::pybind11 ALIAS pybind11)  # to match exported target
+add_library(pybind11::pybind11 ALIAS pybind11) # to match exported target
 
-target_include_directories(pybind11 ${pybind11_system} INTERFACE $<BUILD_INTERFACE:${PYBIND11_INCLUDE_DIR}>
-                                                                 $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
+target_include_directories(
+  pybind11 ${pybind11_system} INTERFACE $<BUILD_INTERFACE:${PYBIND11_INCLUDE_DIR}>
+                                        $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 # Only add Python for build - must be added during the import for config since it has to be re-discovered.
 target_include_directories(pybind11 SYSTEM INTERFACE $<BUILD_INTERFACE:${PYTHON_INCLUDE_DIRS}>)
 
 if(CMAKE_VERSION VERSION_LESS 3.13)
-    target_compile_features(
-        pybind11
-      INTERFACE
-        cxx_inheriting_constructors
-        cxx_user_literals
-        cxx_right_angle_brackets
-      )
+  target_compile_features(pybind11 INTERFACE cxx_inheriting_constructors cxx_user_literals
+                                             cxx_right_angle_brackets)
 else()
-    # This was added in CMake 3.8, but we are keeping a consistent breaking
-    # point for the config file at 3.13. A config generated by CMake 3.13+
-    # can only be read in 3.13+ due to the SHELL usage later, so this is safe to do.
-    target_compile_features(pybind11 INTERFACE cxx_std_11)
+  # This was added in CMake 3.8, but we are keeping a consistent breaking
+  # point for the config file at 3.13. A config generated by CMake 3.13+
+  # can only be read in 3.13+ due to the SHELL usage later, so this is safe to do.
+  target_compile_features(pybind11 INTERFACE cxx_std_11)
 endif()
 
 add_library(module INTERFACE)
@@ -167,23 +167,26 @@ target_link_libraries(module INTERFACE pybind11::pybind11)
 
 # See https://github.com/Kitware/CMake/blob/master/Modules/CMakePlatformId.h.in for platform IDs
 # Note: CMake 3.15 allows $<PLATFORM_ID:Windows,Cygwin>
-target_link_libraries(module INTERFACE "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>")
+target_link_libraries(
+  module
+  INTERFACE
+    "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>")
 
 if(CMAKE_VERSION VERSION_LESS 3.13)
-    target_link_libraries(module INTERFACE "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
+  target_link_libraries(module INTERFACE "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
 else()
-    # SHELL (3.12+) forces this to remain together, and link_options was added in 3.13+
-    # This is safer, because you are ensured the deduplication pass in CMake will not consider
-    # these separate and remove one but not the other.
-    target_link_options(module INTERFACE "$<$<PLATFORM_ID:Darwin>:SHELL:-undefined dynamic_lookup>")
+  # SHELL (3.12+) forces this to remain together, and link_options was added in 3.13+
+  # This is safer, because you are ensured the deduplication pass in CMake will not consider
+  # these separate and remove one but not the other.
+  target_link_options(module INTERFACE "$<$<PLATFORM_ID:Darwin>:SHELL:-undefined dynamic_lookup>")
 endif()
 
-
 # Workaround for Python 2.7 and C++17 (C++14 as a warning) incompatibility
 # This adds the flags -Wno-register and -Wno-deprecated-register if the compiler
 # is Clang 3.9+ or AppleClang and the compile language is CXX, or /wd5033 for MSVC (all languages,
 # since MSVC didn't recognize COMPILE_LANGUAGE until CMake 3.11+).
-set(clang_4plus "$<AND:$<CXX_COMPILER_ID:Clang>,$<NOT:$<VERSION_LESS:$<CXX_COMPILER_VERSION>,3.9>>>")
+set(clang_4plus
+    "$<AND:$<CXX_COMPILER_ID:Clang>,$<NOT:$<VERSION_LESS:$<CXX_COMPILER_VERSION>,3.9>>>")
 set(no_register "$<OR:${clang_4plus},$<CXX_COMPILER_ID:AppleClang>>")
 set(cxx_no_register "$<AND:$<COMPILE_LANGUAGE:CXX>,${no_register}>")
 set(msvc "$<CXX_COMPILER_ID:MSVC>")
@@ -196,58 +199,50 @@ add_library(pybind11::embed ALIAS embed)
 target_link_libraries(embed INTERFACE pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
 
 if(PYBIND11_INSTALL)
-    install(DIRECTORY ${PYBIND11_INCLUDE_DIR}/pybind11 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
-    # GNUInstallDirs "DATADIR" wrong here; CMake search path wants "share".
-    set(PYBIND11_CMAKECONFIG_INSTALL_DIR "share/cmake/${PROJECT_NAME}" CACHE STRING "install path for pybind11Config.cmake")
-
-    configure_package_config_file(tools/${PROJECT_NAME}Config.cmake.in
-                                  "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
-                                  INSTALL_DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
-
-    if(CMAKE_VERSION VERSION_LESS 3.14)
-        # Remove CMAKE_SIZEOF_VOID_P from ConfigVersion.cmake since the library does
-        # not depend on architecture specific settings or libraries.
-        set(_PYBIND11_CMAKE_SIZEOF_VOID_P ${CMAKE_SIZEOF_VOID_P})
-        unset(CMAKE_SIZEOF_VOID_P)
-
-        write_basic_package_version_file(
-            ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-          VERSION
-            ${PROJECT_VERSION}
-          COMPATIBILITY
-            AnyNewerVersion
-        )
-
-        set(CMAKE_SIZEOF_VOID_P ${_PYBIND11_CMAKE_SIZEOF_VOID_P})
-    else()
-        # CMake 3.14+ natively supports header-only libraries
-        write_basic_package_version_file(
-            ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-          VERSION
-            ${PROJECT_VERSION}
-          COMPATIBILITY
-            AnyNewerVersion
-          ARCH_INDEPENDENT
-        )
-    endif()
-
-    install(
-      FILES
-        ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
-        ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-        tools/FindPythonLibsNew.cmake
-        tools/pybind11Tools.cmake
-      DESTINATION
-        ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
-
-    if(NOT PYBIND11_EXPORT_NAME)
-        set(PYBIND11_EXPORT_NAME "${PROJECT_NAME}Targets")
-    endif()
-
-    install(TARGETS pybind11 module embed
-            EXPORT "${PYBIND11_EXPORT_NAME}")
-
-    install(EXPORT "${PYBIND11_EXPORT_NAME}"
-            NAMESPACE "pybind11::"
-            DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
+  install(DIRECTORY ${PYBIND11_INCLUDE_DIR}/pybind11 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
+  # GNUInstallDirs "DATADIR" wrong here; CMake search path wants "share".
+  set(PYBIND11_CMAKECONFIG_INSTALL_DIR
+      "share/cmake/${PROJECT_NAME}"
+      CACHE STRING "install path for pybind11Config.cmake")
+
+  configure_package_config_file(
+    tools/${PROJECT_NAME}Config.cmake.in "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
+    INSTALL_DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
+
+  if(CMAKE_VERSION VERSION_LESS 3.14)
+    # Remove CMAKE_SIZEOF_VOID_P from ConfigVersion.cmake since the library does
+    # not depend on architecture specific settings or libraries.
+    set(_PYBIND11_CMAKE_SIZEOF_VOID_P ${CMAKE_SIZEOF_VOID_P})
+    unset(CMAKE_SIZEOF_VOID_P)
+
+    write_basic_package_version_file(
+      ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+      VERSION ${PROJECT_VERSION}
+      COMPATIBILITY AnyNewerVersion)
+
+    set(CMAKE_SIZEOF_VOID_P ${_PYBIND11_CMAKE_SIZEOF_VOID_P})
+  else()
+    # CMake 3.14+ natively supports header-only libraries
+    write_basic_package_version_file(
+      ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+      VERSION ${PROJECT_VERSION}
+      COMPATIBILITY AnyNewerVersion ARCH_INDEPENDENT)
+  endif()
+
+  install(
+    FILES ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
+          ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+          tools/FindPythonLibsNew.cmake tools/pybind11Tools.cmake
+    DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
+
+  if(NOT PYBIND11_EXPORT_NAME)
+    set(PYBIND11_EXPORT_NAME "${PROJECT_NAME}Targets")
+  endif()
+
+  install(TARGETS pybind11 module embed EXPORT "${PYBIND11_EXPORT_NAME}")
+
+  install(
+    EXPORT "${PYBIND11_EXPORT_NAME}"
+    NAMESPACE "pybind11::"
+    DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
 endif()
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index cab273bc1d..5dea63acd1 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -10,84 +10,91 @@ cmake_minimum_required(VERSION 3.7)
 # VERSION 3.7...3.18, but some versions of VS have a patched CMake 3.11
 # that do not work properly with this syntax, so using the following workaround:
 if(${CMAKE_VERSION} VERSION_LESS 3.18)
-    cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
+  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-    cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.18)
 endif()
 
 # There's no harm in including a project in a project
 project(pybind11_tests CXX)
 
-option(PYBIND11_WERROR  "Report all warnings as errors"  OFF)
+option(PYBIND11_WERROR "Report all warnings as errors" OFF)
 option(DOWNLOAD_EIGEN "Download EIGEN (requires CMake 3.11+)" OFF)
-set(PYBIND11_TEST_OVERRIDE "" CACHE STRING "Tests from ;-separated list of *.cpp files will be built instead of all tests")
+set(PYBIND11_TEST_OVERRIDE
+    ""
+    CACHE STRING "Tests from ;-separated list of *.cpp files will be built instead of all tests")
 
 if(CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
-    # We're being loaded directly, i.e. not via add_subdirectory, so make this
-    # work as its own project and load the pybind11Config to get the tools we need
-    find_package(pybind11 REQUIRED CONFIG)
+  # We're being loaded directly, i.e. not via add_subdirectory, so make this
+  # work as its own project and load the pybind11Config to get the tools we need
+  find_package(pybind11 REQUIRED CONFIG)
 endif()
 
 if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
   message(STATUS "Setting tests build type to MinSizeRel as none was specified")
-  set(CMAKE_BUILD_TYPE MinSizeRel CACHE STRING "Choose the type of build." FORCE)
-  set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release"
-    "MinSizeRel" "RelWithDebInfo")
+  set(CMAKE_BUILD_TYPE
+      MinSizeRel
+      CACHE STRING "Choose the type of build." FORCE)
+  set_property(CACHE CMAKE_BUILD_TYPE PROPERTY STRINGS "Debug" "Release" "MinSizeRel"
+                                               "RelWithDebInfo")
 endif()
 
 # Full set of test files (you can override these; see below)
 set(PYBIND11_TEST_FILES
-  test_async.cpp
-  test_buffers.cpp
-  test_builtin_casters.cpp
-  test_call_policies.cpp
-  test_callbacks.cpp
-  test_chrono.cpp
-  test_class.cpp
-  test_constants_and_functions.cpp
-  test_copy_move.cpp
-  test_custom_type_casters.cpp
-  test_docstring_options.cpp
-  test_eigen.cpp
-  test_enum.cpp
-  test_eval.cpp
-  test_exceptions.cpp
-  test_factory_constructors.cpp
-  test_gil_scoped.cpp
-  test_iostream.cpp
-  test_kwargs_and_defaults.cpp
-  test_local_bindings.cpp
-  test_methods_and_attributes.cpp
-  test_modules.cpp
-  test_multiple_inheritance.cpp
-  test_numpy_array.cpp
-  test_numpy_dtypes.cpp
-  test_numpy_vectorize.cpp
-  test_opaque_types.cpp
-  test_operator_overloading.cpp
-  test_pickling.cpp
-  test_pytypes.cpp
-  test_sequences_and_iterators.cpp
-  test_smart_ptr.cpp
-  test_stl.cpp
-  test_stl_binders.cpp
-  test_tagbased_polymorphic.cpp
-  test_union.cpp
-  test_virtual_functions.cpp
-)
+    test_async.cpp
+    test_buffers.cpp
+    test_builtin_casters.cpp
+    test_call_policies.cpp
+    test_callbacks.cpp
+    test_chrono.cpp
+    test_class.cpp
+    test_constants_and_functions.cpp
+    test_copy_move.cpp
+    test_custom_type_casters.cpp
+    test_docstring_options.cpp
+    test_eigen.cpp
+    test_enum.cpp
+    test_eval.cpp
+    test_exceptions.cpp
+    test_factory_constructors.cpp
+    test_gil_scoped.cpp
+    test_iostream.cpp
+    test_kwargs_and_defaults.cpp
+    test_local_bindings.cpp
+    test_methods_and_attributes.cpp
+    test_modules.cpp
+    test_multiple_inheritance.cpp
+    test_numpy_array.cpp
+    test_numpy_dtypes.cpp
+    test_numpy_vectorize.cpp
+    test_opaque_types.cpp
+    test_operator_overloading.cpp
+    test_pickling.cpp
+    test_pytypes.cpp
+    test_sequences_and_iterators.cpp
+    test_smart_ptr.cpp
+    test_stl.cpp
+    test_stl_binders.cpp
+    test_tagbased_polymorphic.cpp
+    test_union.cpp
+    test_virtual_functions.cpp)
 
 # Invoking cmake with something like:
 #     cmake -DPYBIND11_TEST_OVERRIDE="test_callbacks.cpp;test_picking.cpp" ..
 # lets you override the tests that get compiled and run.  You can restore to all tests with:
 #     cmake -DPYBIND11_TEST_OVERRIDE= ..
-if (PYBIND11_TEST_OVERRIDE)
+if(PYBIND11_TEST_OVERRIDE)
   set(PYBIND11_TEST_FILES ${PYBIND11_TEST_OVERRIDE})
 endif()
 
 # Skip test_async for Python < 3.5
 list(FIND PYBIND11_TEST_FILES test_async.cpp PYBIND11_TEST_FILES_ASYNC_I)
-if((PYBIND11_TEST_FILES_ASYNC_I GREATER -1) AND ("${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}" VERSION_LESS 3.5))
-  message(STATUS "Skipping test_async because Python version ${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR} < 3.5")
+if((PYBIND11_TEST_FILES_ASYNC_I GREATER -1) AND ("${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}"
+                                                 VERSION_LESS 3.5))
+  message(
+    STATUS
+      "Skipping test_async because Python version ${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR} < 3.5"
+  )
   list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_ASYNC_I})
 endif()
 
@@ -96,16 +103,10 @@ string(REPLACE ".cpp" ".py" PYBIND11_PYTEST_FILES "${PYBIND11_TEST_FILES}")
 # Contains the set of test files that require pybind11_cross_module_tests to be
 # built; if none of these are built (i.e. because TEST_OVERRIDE is used and
 # doesn't include them) the second module doesn't get built.
-set(PYBIND11_CROSS_MODULE_TESTS
-  test_exceptions.py
-  test_local_bindings.py
-  test_stl.py
-  test_stl_binders.py
-)
+set(PYBIND11_CROSS_MODULE_TESTS test_exceptions.py test_local_bindings.py test_stl.py
+                                test_stl_binders.py)
 
-set(PYBIND11_CROSS_MODULE_GIL_TESTS
-  test_gil_scoped.py
-)
+set(PYBIND11_CROSS_MODULE_GIL_TESTS test_gil_scoped.py)
 
 # Check if Eigen is available; if not, remove from PYBIND11_TEST_FILES (but
 # keep it in PYBIND11_PYTEST_FILES, so that we get the "eigen is not installed"
@@ -126,8 +127,7 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     FetchContent_Declare(
       eigen
       GIT_REPOSITORY https://gitlab.com/libeigen/eigen.git
-      GIT_TAG ${EIGEN3_VERSION_STRING}
-    )
+      GIT_TAG ${EIGEN3_VERSION_STRING})
 
     FetchContent_GetProperties(eigen)
     if(NOT eigen_POPULATED)
@@ -139,13 +139,13 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
     set(EIGEN3_FOUND TRUE)
   else()
     find_package(Eigen3 3.2.7 QUIET CONFIG)
-    if (EIGEN3_FOUND)
-      if (EIGEN3_VERSION_STRING AND NOT EIGEN3_VERSION_STRING VERSION_LESS 3.3.1)
+    if(EIGEN3_FOUND)
+      if(EIGEN3_VERSION_STRING AND NOT EIGEN3_VERSION_STRING VERSION_LESS 3.3.1)
         set(PYBIND11_EIGEN_VIA_TARGET TRUE)
       endif()
     endif()
 
-    if (NOT EIGEN3_FOUND)
+    if(NOT EIGEN3_FOUND)
       # Couldn't load via target, so fall back to allowing module mode finding, which will pick up
       # tools/FindEigen3.cmake
       find_package(Eigen3 3.2.7 QUIET)
@@ -174,7 +174,8 @@ function(pybind11_enable_warnings target_name)
   if(MSVC)
     target_compile_options(${target_name} PRIVATE /W4)
   elseif(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Intel|Clang)")
-      target_compile_options(${target_name} PRIVATE -Wall -Wextra -Wconversion -Wcast-qual -Wdeprecated)
+    target_compile_options(${target_name} PRIVATE -Wall -Wextra -Wconversion -Wcast-qual
+                                                  -Wdeprecated)
   endif()
 
   if(PYBIND11_WERROR)
@@ -186,7 +187,9 @@ function(pybind11_enable_warnings target_name)
   endif()
 
   # Needs to be readded since the ordering requires these to be after the ones above
-  if(CMAKE_CXX_STANDARD AND CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND PYTHON_VERSION VERSION_LESS 3.0)
+  if(CMAKE_CXX_STANDARD
+     AND CMAKE_CXX_COMPILER_ID MATCHES "Clang"
+     AND PYTHON_VERSION VERSION_LESS 3.0)
     if(CMAKE_CXX_STANDARD LESS 17)
       target_compile_options(${target_name} PUBLIC -Wno-deprecated-register)
     else()
@@ -200,7 +203,7 @@ set(test_targets pybind11_tests)
 # Build pybind11_cross_module_tests if any test_whatever.py are being built that require it
 foreach(t ${PYBIND11_CROSS_MODULE_TESTS})
   list(FIND PYBIND11_PYTEST_FILES ${t} i)
-  if (i GREATER -1)
+  if(i GREATER -1)
     list(APPEND test_targets pybind11_cross_module_tests)
     break()
   endif()
@@ -208,7 +211,7 @@ endforeach()
 
 foreach(t ${PYBIND11_CROSS_MODULE_GIL_TESTS})
   list(FIND PYBIND11_PYTEST_FILES ${t} i)
-  if (i GREATER -1)
+  if(i GREATER -1)
     list(APPEND test_targets cross_module_gil_utils)
     break()
   endif()
@@ -230,7 +233,7 @@ foreach(target ${test_targets})
   endif()
 
   if(EIGEN3_FOUND)
-    if (PYBIND11_EIGEN_VIA_TARGET)
+    if(PYBIND11_EIGEN_VIA_TARGET)
       target_link_libraries(${target} PRIVATE Eigen3::Eigen)
     else()
       target_include_directories(${target} PRIVATE ${EIGEN3_INCLUDE_DIR})
@@ -255,8 +258,11 @@ endforeach()
 
 # Make sure pytest is found or produce a fatal error
 if(NOT PYBIND11_PYTEST_FOUND)
-  execute_process(COMMAND ${PYTHON_EXECUTABLE} -c "import pytest; print(pytest.__version__)"
-                  RESULT_VARIABLE pytest_not_found OUTPUT_VARIABLE pytest_version ERROR_QUIET)
+  execute_process(
+    COMMAND ${PYTHON_EXECUTABLE} -c "import pytest; print(pytest.__version__)"
+    RESULT_VARIABLE pytest_not_found
+    OUTPUT_VARIABLE pytest_version
+    ERROR_QUIET)
   if(pytest_not_found)
     message(FATAL_ERROR "Running the tests requires pytest. Please install it manually"
                         " (try: ${PYTHON_EXECUTABLE} -m pip install pytest)")
@@ -264,16 +270,25 @@ if(NOT PYBIND11_PYTEST_FOUND)
     message(FATAL_ERROR "Running the tests requires pytest >= 3.0. Found: ${pytest_version}"
                         "Please update it (try: ${PYTHON_EXECUTABLE} -m pip install -U pytest)")
   endif()
-  set(PYBIND11_PYTEST_FOUND TRUE CACHE INTERNAL "")
+  set(PYBIND11_PYTEST_FOUND
+      TRUE
+      CACHE INTERNAL "")
 endif()
 
 # A single command to compile and run the tests
-add_custom_target(pytest COMMAND ${PYTHON_EXECUTABLE} -m pytest ${PYBIND11_PYTEST_FILES}
-                  DEPENDS ${test_targets} WORKING_DIRECTORY ${testdir} USES_TERMINAL)
+add_custom_target(
+  pytest
+  COMMAND ${PYTHON_EXECUTABLE} -m pytest ${PYBIND11_PYTEST_FILES}
+  DEPENDS ${test_targets}
+  WORKING_DIRECTORY ${testdir}
+  USES_TERMINAL)
 
 if(PYBIND11_TEST_OVERRIDE)
-  add_custom_command(TARGET pytest POST_BUILD
-    COMMAND ${CMAKE_COMMAND} -E echo "Note: not all tests run: -DPYBIND11_TEST_OVERRIDE is in effect")
+  add_custom_command(
+    TARGET pytest
+    POST_BUILD
+    COMMAND ${CMAKE_COMMAND} -E echo
+            "Note: not all tests run: -DPYBIND11_TEST_OVERRIDE is in effect")
 endif()
 
 # Add a check target to run all the tests, starting with pytest (we add dependencies to this below)
@@ -287,11 +302,10 @@ endif()
 
 # Add a post-build comment to show the primary test suite .so size and, if a previous size, compare it:
 add_custom_command(
-  TARGET
-    pybind11_tests
-  POST_BUILD COMMAND
-    ${PYTHON_EXECUTABLE}
-    ${CMAKE_CURRENT_SOURCE_DIR}/../tools/libsize.py
+  TARGET pybind11_tests
+  POST_BUILD
+  COMMAND
+    ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../tools/libsize.py
     $<TARGET_FILE:pybind11_tests>
     ${CMAKE_CURRENT_BINARY_DIR}/sosize-$<TARGET_FILE_NAME:pybind11_tests>.txt)
 
diff --git a/tests/test_cmake_build/CMakeLists.txt b/tests/test_cmake_build/CMakeLists.txt
index fd8c80304a..53228f0eb4 100644
--- a/tests/test_cmake_build/CMakeLists.txt
+++ b/tests/test_cmake_build/CMakeLists.txt
@@ -1,12 +1,12 @@
 add_custom_target(test_cmake_build)
 
-
 function(pybind11_add_build_test name)
   cmake_parse_arguments(ARG "INSTALL" "" "" ${ARGN})
 
-  set(build_options "-DCMAKE_PREFIX_PATH=${pybind11_BINARY_DIR}/mock_install"
-                    "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
-                    "-DPYTHON_EXECUTABLE:FILEPATH=${PYTHON_EXECUTABLE}")
+  set(build_options
+      "-DCMAKE_PREFIX_PATH=${pybind11_BINARY_DIR}/mock_install"
+      "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
+      "-DPYTHON_EXECUTABLE:FILEPATH=${PYTHON_EXECUTABLE}")
 
   if(CMAKE_CXX_STANDARD)
     list(APPEND build_options "-DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}")
@@ -16,17 +16,25 @@ function(pybind11_add_build_test name)
     list(APPEND build_options "-DPYBIND11_PROJECT_DIR=${pybind11_SOURCE_DIR}")
   endif()
 
-  add_custom_target(test_${name} ${CMAKE_CTEST_COMMAND}
-    --build-and-test "${CMAKE_CURRENT_SOURCE_DIR}/${name}"
-                     "${CMAKE_CURRENT_BINARY_DIR}/${name}"
-    --build-config Release
+  add_custom_target(
+    test_${name}
+    ${CMAKE_CTEST_COMMAND}
+    --build-and-test
+    "${CMAKE_CURRENT_SOURCE_DIR}/${name}"
+    "${CMAKE_CURRENT_BINARY_DIR}/${name}"
+    --build-config
+    Release
     --build-noclean
-    --build-generator ${CMAKE_GENERATOR}
-    $<$<BOOL:${CMAKE_GENERATOR_PLATFORM}>:--build-generator-platform> ${CMAKE_GENERATOR_PLATFORM}
-    --build-makeprogram ${CMAKE_MAKE_PROGRAM}
-    --build-target check
-    --build-options ${build_options}
-  )
+    --build-generator
+    ${CMAKE_GENERATOR}
+    $<$<BOOL:${CMAKE_GENERATOR_PLATFORM}>:--build-generator-platform>
+    ${CMAKE_GENERATOR_PLATFORM}
+    --build-makeprogram
+    ${CMAKE_MAKE_PROGRAM}
+    --build-target
+    check
+    --build-options
+    ${build_options})
   if(ARG_INSTALL)
     add_dependencies(test_${name} mock_install)
   endif()
@@ -40,10 +48,9 @@ if(NOT ${PYTHON_MODULE_EXTENSION} MATCHES "pypy")
 endif()
 
 if(PYBIND11_INSTALL)
-  add_custom_target(mock_install ${CMAKE_COMMAND}
-    "-DCMAKE_INSTALL_PREFIX=${pybind11_BINARY_DIR}/mock_install"
-    -P "${pybind11_BINARY_DIR}/cmake_install.cmake"
-  )
+  add_custom_target(
+    mock_install ${CMAKE_COMMAND} "-DCMAKE_INSTALL_PREFIX=${pybind11_BINARY_DIR}/mock_install" -P
+                 "${pybind11_BINARY_DIR}/cmake_install.cmake")
 
   pybind11_add_build_test(installed_function INSTALL)
   pybind11_add_build_test(installed_target INSTALL)
diff --git a/tests/test_cmake_build/installed_embed/CMakeLists.txt b/tests/test_cmake_build/installed_embed/CMakeLists.txt
index 80ac2f0e92..78855afa26 100644
--- a/tests/test_cmake_build/installed_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_embed/CMakeLists.txt
@@ -8,7 +8,6 @@ message(STATUS "Found pybind11 v${pybind11_VERSION}: ${pybind11_INCLUDE_DIRS}")
 add_executable(test_cmake_build ../embed.cpp)
 target_link_libraries(test_cmake_build PRIVATE pybind11::embed)
 
-
 # Do not treat includes from IMPORTED target as SYSTEM (Python headers in pybind11::embed).
 # This may be needed to resolve header conflicts, e.g. between Python release and debug headers.
 set_target_properties(test_cmake_build PROPERTIES NO_SYSTEM_FROM_IMPORTED ON)
diff --git a/tests/test_cmake_build/installed_function/CMakeLists.txt b/tests/test_cmake_build/installed_function/CMakeLists.txt
index a8c0130d91..3ad5445e3f 100644
--- a/tests/test_cmake_build/installed_function/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_function/CMakeLists.txt
@@ -8,5 +8,12 @@ message(STATUS "Found pybind11 v${pybind11_VERSION}: ${pybind11_INCLUDE_DIRS}")
 
 pybind11_add_module(test_cmake_build SHARED NO_EXTRAS ../main.cpp)
 
-add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
-                  ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME})
+add_custom_target(
+  check
+  ${CMAKE_COMMAND}
+  -E
+  env
+  PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
+  ${PYTHON_EXECUTABLE}
+  ${PROJECT_SOURCE_DIR}/../test.py
+  ${PROJECT_NAME})
diff --git a/tests/test_cmake_build/installed_target/CMakeLists.txt b/tests/test_cmake_build/installed_target/CMakeLists.txt
index a172c20cfd..348c419cd3 100644
--- a/tests/test_cmake_build/installed_target/CMakeLists.txt
+++ b/tests/test_cmake_build/installed_target/CMakeLists.txt
@@ -18,5 +18,12 @@ set_target_properties(test_cmake_build PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX
 # This may be needed to resolve header conflicts, e.g. between Python release and debug headers.
 set_target_properties(test_cmake_build PROPERTIES NO_SYSTEM_FROM_IMPORTED ON)
 
-add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
-                  ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME})
+add_custom_target(
+  check
+  ${CMAKE_COMMAND}
+  -E
+  env
+  PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
+  ${PYTHON_EXECUTABLE}
+  ${PROJECT_SOURCE_DIR}/../test.py
+  ${PROJECT_NAME})
diff --git a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
index 170ec5300d..eea0eeea3d 100644
--- a/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_embed/CMakeLists.txt
@@ -1,7 +1,9 @@
 cmake_minimum_required(VERSION 3.7)
 project(test_subdirectory_embed CXX)
 
-set(PYBIND11_INSTALL ON CACHE BOOL "")
+set(PYBIND11_INSTALL
+    ON
+    CACHE BOOL "")
 set(PYBIND11_EXPORT_NAME test_export)
 
 add_subdirectory(${PYBIND11_PROJECT_DIR} pybind11)
@@ -16,10 +18,10 @@ add_custom_target(check $<TARGET_FILE:test_cmake_build> ${PROJECT_SOURCE_DIR}/..
 add_library(test_embed_lib ../embed.cpp)
 target_link_libraries(test_embed_lib PRIVATE pybind11::embed)
 
-install(TARGETS test_embed_lib
-        EXPORT  test_export
-        ARCHIVE DESTINATION bin
-        LIBRARY DESTINATION lib
-        RUNTIME DESTINATION lib)
-install(EXPORT      test_export
-        DESTINATION lib/cmake/test_export/test_export-Targets.cmake)
+install(
+  TARGETS test_embed_lib
+  EXPORT test_export
+  ARCHIVE DESTINATION bin
+  LIBRARY DESTINATION lib
+  RUNTIME DESTINATION lib)
+install(EXPORT test_export DESTINATION lib/cmake/test_export/test_export-Targets.cmake)
diff --git a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
index f4d4e35833..e4518044ed 100644
--- a/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_function/CMakeLists.txt
@@ -4,5 +4,12 @@ project(test_subdirectory_module CXX)
 add_subdirectory(${PYBIND11_PROJECT_DIR} pybind11)
 pybind11_add_module(test_cmake_build THIN_LTO ../main.cpp)
 
-add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
-                  ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME})
+add_custom_target(
+  check
+  ${CMAKE_COMMAND}
+  -E
+  env
+  PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
+  ${PYTHON_EXECUTABLE}
+  ${PROJECT_SOURCE_DIR}/../test.py
+  ${PROJECT_NAME})
diff --git a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
index 01acba426f..f84140ce04 100644
--- a/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
+++ b/tests/test_cmake_build/subdirectory_target/CMakeLists.txt
@@ -11,5 +11,12 @@ target_link_libraries(test_cmake_build PRIVATE pybind11::module)
 set_target_properties(test_cmake_build PROPERTIES PREFIX "${PYTHON_MODULE_PREFIX}"
                                                   SUFFIX "${PYTHON_MODULE_EXTENSION}")
 
-add_custom_target(check ${CMAKE_COMMAND} -E env PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
-                  ${PYTHON_EXECUTABLE} ${PROJECT_SOURCE_DIR}/../test.py ${PROJECT_NAME})
+add_custom_target(
+  check
+  ${CMAKE_COMMAND}
+  -E
+  env
+  PYTHONPATH=$<TARGET_FILE_DIR:test_cmake_build>
+  ${PYTHON_EXECUTABLE}
+  ${PROJECT_SOURCE_DIR}/../test.py
+  ${PROJECT_NAME})
diff --git a/tests/test_embed/CMakeLists.txt b/tests/test_embed/CMakeLists.txt
index 495b0fcbfa..25972701fc 100644
--- a/tests/test_embed/CMakeLists.txt
+++ b/tests/test_embed/CMakeLists.txt
@@ -1,5 +1,5 @@
 if(${PYTHON_MODULE_EXTENSION} MATCHES "pypy")
-  add_custom_target(cpptest)  # Dummy target on PyPy. Embedding is not supported.
+  add_custom_target(cpptest) # Dummy target on PyPy. Embedding is not supported.
   set(_suppress_unused_variable_warning "${DOWNLOAD_CATCH}")
   return()
 endif()
@@ -13,10 +13,7 @@ else()
   return()
 endif()
 
-add_executable(test_embed
-  catch.cpp
-  test_interpreter.cpp
-)
+add_executable(test_embed catch.cpp test_interpreter.cpp)
 target_include_directories(test_embed PRIVATE "${CATCH_INCLUDE_DIR}")
 pybind11_enable_warnings(test_embed)
 
@@ -25,14 +22,18 @@ target_link_libraries(test_embed PRIVATE pybind11::embed)
 find_package(Threads REQUIRED)
 target_link_libraries(test_embed PUBLIC Threads::Threads)
 
-add_custom_target(cpptest COMMAND "$<TARGET_FILE:test_embed>"
-                  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
+add_custom_target(
+  cpptest
+  COMMAND "$<TARGET_FILE:test_embed>"
+  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
 
 pybind11_add_module(external_module THIN_LTO external_module.cpp)
-set_target_properties(external_module PROPERTIES LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}")
+set_target_properties(external_module PROPERTIES LIBRARY_OUTPUT_DIRECTORY
+                                                 "${CMAKE_CURRENT_SOURCE_DIR}")
 foreach(config ${CMAKE_CONFIGURATION_TYPES})
   string(TOUPPER ${config} config)
-  set_target_properties(external_module PROPERTIES LIBRARY_OUTPUT_DIRECTORY_${config} "${CMAKE_CURRENT_SOURCE_DIR}")
+  set_target_properties(external_module PROPERTIES LIBRARY_OUTPUT_DIRECTORY_${config}
+                                                   "${CMAKE_CURRENT_SOURCE_DIR}")
 endforeach()
 add_dependencies(cpptest external_module)
 
diff --git a/tools/FindCatch.cmake b/tools/FindCatch.cmake
index ad4a4a5938..ade66c79e6 100644
--- a/tools/FindCatch.cmake
+++ b/tools/FindCatch.cmake
@@ -19,9 +19,14 @@ endif()
 
 # Extract the version number from catch.hpp
 function(_get_catch_version)
-  file(STRINGS "${CATCH_INCLUDE_DIR}/catch.hpp" version_line REGEX "Catch v.*" LIMIT_COUNT 1)
+  file(
+    STRINGS "${CATCH_INCLUDE_DIR}/catch.hpp" version_line
+    REGEX "Catch v.*"
+    LIMIT_COUNT 1)
   if(version_line MATCHES "Catch v([0-9]+)\\.([0-9]+)\\.([0-9]+)")
-    set(CATCH_VERSION "${CMAKE_MATCH_1}.${CMAKE_MATCH_2}.${CMAKE_MATCH_3}" PARENT_SCOPE)
+    set(CATCH_VERSION
+        "${CMAKE_MATCH_1}.${CMAKE_MATCH_2}.${CMAKE_MATCH_3}"
+        PARENT_SCOPE)
   endif()
 endfunction()
 
@@ -34,11 +39,16 @@ function(_download_catch version destination_dir)
   if(error)
     message(FATAL_ERROR "Could not download ${url}")
   endif()
-  set(CATCH_INCLUDE_DIR "${destination_dir}" CACHE INTERNAL "")
+  set(CATCH_INCLUDE_DIR
+      "${destination_dir}"
+      CACHE INTERNAL "")
 endfunction()
 
 # Look for catch locally
-find_path(CATCH_INCLUDE_DIR NAMES catch.hpp PATH_SUFFIXES catch2)
+find_path(
+  CATCH_INCLUDE_DIR
+  NAMES catch.hpp
+  PATH_SUFFIXES catch2)
 if(CATCH_INCLUDE_DIR)
   _get_catch_version()
 endif()
diff --git a/tools/FindEigen3.cmake b/tools/FindEigen3.cmake
index 66ffe8e1e5..98ab43d9e6 100644
--- a/tools/FindEigen3.cmake
+++ b/tools/FindEigen3.cmake
@@ -26,17 +26,21 @@ if(NOT Eigen3_FIND_VERSION)
     set(Eigen3_FIND_VERSION_PATCH 0)
   endif(NOT Eigen3_FIND_VERSION_PATCH)
 
-  set(Eigen3_FIND_VERSION "${Eigen3_FIND_VERSION_MAJOR}.${Eigen3_FIND_VERSION_MINOR}.${Eigen3_FIND_VERSION_PATCH}")
+  set(Eigen3_FIND_VERSION
+      "${Eigen3_FIND_VERSION_MAJOR}.${Eigen3_FIND_VERSION_MINOR}.${Eigen3_FIND_VERSION_PATCH}")
 endif(NOT Eigen3_FIND_VERSION)
 
 macro(_eigen3_check_version)
   file(READ "${EIGEN3_INCLUDE_DIR}/Eigen/src/Core/util/Macros.h" _eigen3_version_header)
 
-  string(REGEX MATCH "define[ \t]+EIGEN_WORLD_VERSION[ \t]+([0-9]+)" _eigen3_world_version_match "${_eigen3_version_header}")
+  string(REGEX MATCH "define[ \t]+EIGEN_WORLD_VERSION[ \t]+([0-9]+)" _eigen3_world_version_match
+               "${_eigen3_version_header}")
   set(EIGEN3_WORLD_VERSION "${CMAKE_MATCH_1}")
-  string(REGEX MATCH "define[ \t]+EIGEN_MAJOR_VERSION[ \t]+([0-9]+)" _eigen3_major_version_match "${_eigen3_version_header}")
+  string(REGEX MATCH "define[ \t]+EIGEN_MAJOR_VERSION[ \t]+([0-9]+)" _eigen3_major_version_match
+               "${_eigen3_version_header}")
   set(EIGEN3_MAJOR_VERSION "${CMAKE_MATCH_1}")
-  string(REGEX MATCH "define[ \t]+EIGEN_MINOR_VERSION[ \t]+([0-9]+)" _eigen3_minor_version_match "${_eigen3_version_header}")
+  string(REGEX MATCH "define[ \t]+EIGEN_MINOR_VERSION[ \t]+([0-9]+)" _eigen3_minor_version_match
+               "${_eigen3_version_header}")
   set(EIGEN3_MINOR_VERSION "${CMAKE_MATCH_1}")
 
   set(EIGEN3_VERSION ${EIGEN3_WORLD_VERSION}.${EIGEN3_MAJOR_VERSION}.${EIGEN3_MINOR_VERSION})
@@ -53,20 +57,19 @@ macro(_eigen3_check_version)
   endif(NOT EIGEN3_VERSION_OK)
 endmacro(_eigen3_check_version)
 
-if (EIGEN3_INCLUDE_DIR)
+if(EIGEN3_INCLUDE_DIR)
 
   # in cache already
   _eigen3_check_version()
   set(EIGEN3_FOUND ${EIGEN3_VERSION_OK})
 
-else (EIGEN3_INCLUDE_DIR)
+else(EIGEN3_INCLUDE_DIR)
 
-  find_path(EIGEN3_INCLUDE_DIR NAMES signature_of_eigen3_matrix_library
-      PATHS
-      ${CMAKE_INSTALL_PREFIX}/include
-      ${KDE4_INCLUDE_DIR}
-      PATH_SUFFIXES eigen3 eigen
-    )
+  find_path(
+    EIGEN3_INCLUDE_DIR
+    NAMES signature_of_eigen3_matrix_library
+    PATHS ${CMAKE_INSTALL_PREFIX}/include ${KDE4_INCLUDE_DIR}
+    PATH_SUFFIXES eigen3 eigen)
 
   if(EIGEN3_INCLUDE_DIR)
     _eigen3_check_version()
diff --git a/tools/FindPythonLibsNew.cmake b/tools/FindPythonLibsNew.cmake
index 994bb1e03b..cf2a13f67b 100644
--- a/tools/FindPythonLibsNew.cmake
+++ b/tools/FindPythonLibsNew.cmake
@@ -52,23 +52,23 @@
 
 # Checking for the extension makes sure that `LibsNew` was found and not just `Libs`.
 if(PYTHONLIBS_FOUND AND PYTHON_MODULE_EXTENSION)
-    return()
+  return()
 endif()
 
 # Use the Python interpreter to find the libs.
 if(NOT PythonLibsNew_FIND_VERSION)
-    set(PythonLibsNew_FIND_VERSION "")
+  set(PythonLibsNew_FIND_VERSION "")
 endif()
 if(PythonLibsNew_FIND_REQUIRED)
-    find_package(PythonInterp ${PythonLibsNew_FIND_VERSION} REQUIRED)
+  find_package(PythonInterp ${PythonLibsNew_FIND_VERSION} REQUIRED)
 else()
-    find_package(PythonInterp ${PythonLibsNew_FIND_VERSION})
+  find_package(PythonInterp ${PythonLibsNew_FIND_VERSION})
 endif()
 
 if(NOT PYTHONINTERP_FOUND)
-    set(PYTHONLIBS_FOUND FALSE)
-    set(PythonLibsNew_FOUND FALSE)
-    return()
+  set(PYTHONLIBS_FOUND FALSE)
+  set(PythonLibsNew_FOUND FALSE)
+  return()
 endif()
 
 # According to http://stackoverflow.com/questions/646518/python-how-to-detect-debug-interpreter
@@ -77,8 +77,9 @@ endif()
 #
 # The library suffix is from the config var LDVERSION sometimes, otherwise
 # VERSION. VERSION will typically be like "2.7" on unix, and "27" on windows.
-execute_process(COMMAND "${PYTHON_EXECUTABLE}" "-c"
-    "from distutils import sysconfig as s;import sys;import struct;
+execute_process(
+  COMMAND
+    "${PYTHON_EXECUTABLE}" "-c" "from distutils import sysconfig as s;import sys;import struct;
 print('.'.join(str(v) for v in sys.version_info));
 print(sys.prefix);
 print(s.get_python_inc(plat_specific=True));
@@ -90,23 +91,22 @@ print(s.get_config_var('LDVERSION') or s.get_config_var('VERSION'));
 print(s.get_config_var('LIBDIR') or '');
 print(s.get_config_var('MULTIARCH') or '');
 "
-    RESULT_VARIABLE _PYTHON_SUCCESS
-    OUTPUT_VARIABLE _PYTHON_VALUES
-    ERROR_VARIABLE _PYTHON_ERROR_VALUE)
+  RESULT_VARIABLE _PYTHON_SUCCESS
+  OUTPUT_VARIABLE _PYTHON_VALUES
+  ERROR_VARIABLE _PYTHON_ERROR_VALUE)
 
 if(NOT _PYTHON_SUCCESS MATCHES 0)
-    if(PythonLibsNew_FIND_REQUIRED)
-        message(FATAL_ERROR
-            "Python config failure:\n${_PYTHON_ERROR_VALUE}")
-    endif()
-    set(PYTHONLIBS_FOUND FALSE)
-    set(PythonLibsNew_FOUND FALSE)
-    return()
+  if(PythonLibsNew_FIND_REQUIRED)
+    message(FATAL_ERROR "Python config failure:\n${_PYTHON_ERROR_VALUE}")
+  endif()
+  set(PYTHONLIBS_FOUND FALSE)
+  set(PythonLibsNew_FOUND FALSE)
+  return()
 endif()
 
 # Convert the process output into a list
 if(WIN32)
-    string(REGEX REPLACE "\\\\" "/" _PYTHON_VALUES ${_PYTHON_VALUES})
+  string(REGEX REPLACE "\\\\" "/" _PYTHON_VALUES ${_PYTHON_VALUES})
 endif()
 string(REGEX REPLACE ";" "\\\\;" _PYTHON_VALUES ${_PYTHON_VALUES})
 string(REGEX REPLACE "\n" ";" _PYTHON_VALUES ${_PYTHON_VALUES})
@@ -124,16 +124,15 @@ list(GET _PYTHON_VALUES 9 PYTHON_MULTIARCH)
 # Make sure the Python has the same pointer-size as the chosen compiler
 # Skip if CMAKE_SIZEOF_VOID_P is not defined
 if(CMAKE_SIZEOF_VOID_P AND (NOT "${PYTHON_SIZEOF_VOID_P}" STREQUAL "${CMAKE_SIZEOF_VOID_P}"))
-    if(PythonLibsNew_FIND_REQUIRED)
-        math(EXPR _PYTHON_BITS "${PYTHON_SIZEOF_VOID_P} * 8")
-        math(EXPR _CMAKE_BITS "${CMAKE_SIZEOF_VOID_P} * 8")
-        message(FATAL_ERROR
-            "Python config failure: Python is ${_PYTHON_BITS}-bit, "
-            "chosen compiler is  ${_CMAKE_BITS}-bit")
-    endif()
-    set(PYTHONLIBS_FOUND FALSE)
-    set(PythonLibsNew_FOUND FALSE)
-    return()
+  if(PythonLibsNew_FIND_REQUIRED)
+    math(EXPR _PYTHON_BITS "${PYTHON_SIZEOF_VOID_P} * 8")
+    math(EXPR _CMAKE_BITS "${CMAKE_SIZEOF_VOID_P} * 8")
+    message(FATAL_ERROR "Python config failure: Python is ${_PYTHON_BITS}-bit, "
+                        "chosen compiler is  ${_CMAKE_BITS}-bit")
+  endif()
+  set(PYTHONLIBS_FOUND FALSE)
+  set(PythonLibsNew_FOUND FALSE)
+  return()
 endif()
 
 # The built-in FindPython didn't always give the version numbers
@@ -148,79 +147,76 @@ string(REGEX REPLACE "\\\\" "/" PYTHON_INCLUDE_DIR "${PYTHON_INCLUDE_DIR}")
 string(REGEX REPLACE "\\\\" "/" PYTHON_SITE_PACKAGES "${PYTHON_SITE_PACKAGES}")
 
 if(CMAKE_HOST_WIN32)
-    set(PYTHON_LIBRARY
-        "${PYTHON_PREFIX}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
-
-    # when run in a venv, PYTHON_PREFIX points to it. But the libraries remain in the
-    # original python installation. They may be found relative to PYTHON_INCLUDE_DIR.
-    if(NOT EXISTS "${PYTHON_LIBRARY}")
-        get_filename_component(_PYTHON_ROOT ${PYTHON_INCLUDE_DIR} DIRECTORY)
-        set(PYTHON_LIBRARY
-            "${_PYTHON_ROOT}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
-    endif()
-
-    # if we are in MSYS & MINGW, and we didn't find windows python lib, look for system python lib
-    if(DEFINED ENV{MSYSTEM} AND MINGW AND NOT EXISTS "${PYTHON_LIBRARY}")
-        if(PYTHON_MULTIARCH)
-            set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}/${PYTHON_MULTIARCH}" "${PYTHON_LIBDIR}")
-        else()
-            set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}")
-        endif()
-        unset(PYTHON_LIBRARY)
-        find_library(PYTHON_LIBRARY
-            NAMES "python${PYTHON_LIBRARY_SUFFIX}"
-            PATHS ${_PYTHON_LIBS_SEARCH}
-            NO_DEFAULT_PATH)
-    endif()
-
-    # raise an error if the python libs are still not found.
-    if(NOT EXISTS "${PYTHON_LIBRARY}")
-        message(FATAL_ERROR "Python libraries not found")
-    endif()
-
-else()
+  set(PYTHON_LIBRARY "${PYTHON_PREFIX}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
+
+  # when run in a venv, PYTHON_PREFIX points to it. But the libraries remain in the
+  # original python installation. They may be found relative to PYTHON_INCLUDE_DIR.
+  if(NOT EXISTS "${PYTHON_LIBRARY}")
+    get_filename_component(_PYTHON_ROOT ${PYTHON_INCLUDE_DIR} DIRECTORY)
+    set(PYTHON_LIBRARY "${_PYTHON_ROOT}/libs/python${PYTHON_LIBRARY_SUFFIX}.lib")
+  endif()
+
+  # if we are in MSYS & MINGW, and we didn't find windows python lib, look for system python lib
+  if(DEFINED ENV{MSYSTEM}
+     AND MINGW
+     AND NOT EXISTS "${PYTHON_LIBRARY}")
     if(PYTHON_MULTIARCH)
-        set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}/${PYTHON_MULTIARCH}" "${PYTHON_LIBDIR}")
+      set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}/${PYTHON_MULTIARCH}" "${PYTHON_LIBDIR}")
     else()
-        set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}")
-    endif()
-    #message(STATUS "Searching for Python libs in ${_PYTHON_LIBS_SEARCH}")
-    # Probably this needs to be more involved. It would be nice if the config
-    # information the python interpreter itself gave us were more complete.
-    find_library(PYTHON_LIBRARY
-        NAMES "python${PYTHON_LIBRARY_SUFFIX}"
-        PATHS ${_PYTHON_LIBS_SEARCH}
-        NO_DEFAULT_PATH)
-
-    # If all else fails, just set the name/version and let the linker figure out the path.
-    if(NOT PYTHON_LIBRARY)
-        set(PYTHON_LIBRARY python${PYTHON_LIBRARY_SUFFIX})
+      set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}")
     endif()
+    unset(PYTHON_LIBRARY)
+    find_library(
+      PYTHON_LIBRARY
+      NAMES "python${PYTHON_LIBRARY_SUFFIX}"
+      PATHS ${_PYTHON_LIBS_SEARCH}
+      NO_DEFAULT_PATH)
+  endif()
+
+  # raise an error if the python libs are still not found.
+  if(NOT EXISTS "${PYTHON_LIBRARY}")
+    message(FATAL_ERROR "Python libraries not found")
+  endif()
+
+else()
+  if(PYTHON_MULTIARCH)
+    set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}/${PYTHON_MULTIARCH}" "${PYTHON_LIBDIR}")
+  else()
+    set(_PYTHON_LIBS_SEARCH "${PYTHON_LIBDIR}")
+  endif()
+  #message(STATUS "Searching for Python libs in ${_PYTHON_LIBS_SEARCH}")
+  # Probably this needs to be more involved. It would be nice if the config
+  # information the python interpreter itself gave us were more complete.
+  find_library(
+    PYTHON_LIBRARY
+    NAMES "python${PYTHON_LIBRARY_SUFFIX}"
+    PATHS ${_PYTHON_LIBS_SEARCH} NO_DEFAULT_PATH)
+
+  # If all else fails, just set the name/version and let the linker figure out the path.
+  if(NOT PYTHON_LIBRARY)
+    set(PYTHON_LIBRARY python${PYTHON_LIBRARY_SUFFIX})
+  endif()
 endif()
 
-MARK_AS_ADVANCED(
-  PYTHON_LIBRARY
-  PYTHON_INCLUDE_DIR
-)
+mark_as_advanced(PYTHON_LIBRARY PYTHON_INCLUDE_DIR)
 
 # We use PYTHON_INCLUDE_DIR, PYTHON_LIBRARY and PYTHON_DEBUG_LIBRARY for the
 # cache entries because they are meant to specify the location of a single
 # library. We now set the variables listed by the documentation for this
 # module.
-SET(PYTHON_INCLUDE_DIRS "${PYTHON_INCLUDE_DIR}")
-SET(PYTHON_LIBRARIES "${PYTHON_LIBRARY}")
+set(PYTHON_INCLUDE_DIRS "${PYTHON_INCLUDE_DIR}")
+set(PYTHON_LIBRARIES "${PYTHON_LIBRARY}")
 if(NOT PYTHON_DEBUG_LIBRARY)
-    SET(PYTHON_DEBUG_LIBRARY "")
+  set(PYTHON_DEBUG_LIBRARY "")
 endif()
-SET(PYTHON_DEBUG_LIBRARIES "${PYTHON_DEBUG_LIBRARY}")
+set(PYTHON_DEBUG_LIBRARIES "${PYTHON_DEBUG_LIBRARY}")
 
-find_package_message(PYTHON
-    "Found PythonLibs: ${PYTHON_LIBRARY}"
-    "${PYTHON_EXECUTABLE}${PYTHON_VERSION_STRING}")
+find_package_message(PYTHON "Found PythonLibs: ${PYTHON_LIBRARY}"
+                     "${PYTHON_EXECUTABLE}${PYTHON_VERSION_STRING}")
 
 set(PYTHONLIBS_FOUND TRUE)
 set(PythonLibsNew_FOUND TRUE)
 
 if(NOT PYTHON_MODULE_PREFIX)
-    SET(PYTHON_MODULE_PREFIX "")
+  set(PYTHON_MODULE_PREFIX "")
 endif()
diff --git a/tools/pybind11Tools.cmake b/tools/pybind11Tools.cmake
index 742699aca7..49876eb9f6 100644
--- a/tools/pybind11Tools.cmake
+++ b/tools/pybind11Tools.cmake
@@ -10,18 +10,22 @@ cmake_minimum_required(VERSION 3.7)
 # VERSION 3.7...3.18, but some versions of VS have a patched CMake 3.11
 # that do not work properly with this syntax, so using the following workaround:
 if(${CMAKE_VERSION} VERSION_LESS 3.18)
-    cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
+  cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-    cmake_policy(VERSION 3.18)
+  cmake_policy(VERSION 3.18)
 endif()
 
 # Add a CMake parameter for choosing a desired Python version
 if(NOT PYBIND11_PYTHON_VERSION)
-    set(PYBIND11_PYTHON_VERSION "" CACHE STRING "Python version to use for compiling modules")
+  set(PYBIND11_PYTHON_VERSION
+      ""
+      CACHE STRING "Python version to use for compiling modules")
 endif()
 
 # A user can set versions manually too
-set(Python_ADDITIONAL_VERSIONS "3.9;3.8;3.7;3.6;3.5;3.4" CACHE INTERNAL "")
+set(Python_ADDITIONAL_VERSIONS
+    "3.9;3.8;3.7;3.6;3.5;3.4"
+    CACHE INTERNAL "")
 find_package(PythonLibsNew ${PYBIND11_PYTHON_VERSION} REQUIRED)
 
 include(CheckCXXCompilerFlag)
@@ -29,76 +33,80 @@ include(CMakeParseArguments)
 
 # Warn or error if old variable name used
 if(PYBIND11_CPP_STANDARD)
-    if(NOT CMAKE_CXX_STANDARD)
-        string(REGEX MATCH
-            [=[..^]=]
-            VAL
-            "${PYBIND11_CPP_STANDARD}")
-        set(supported_standards 11 14 17 20)
-        if("${VAL}" IN_LIST supported_standards)
-            message(WARNING "USE -DCMAKE_CXX_STANDARD=${VAL} instead of PYBIND11_PYTHON_VERSION")
-            set(CMAKE_CXX_STANDARD ${VAL})
-        else()
-            message(FATAL_ERROR "PYBIND11_CPP_STANDARD should be replaced with CMAKE_CXX_STANDARD")
-        endif()
+  if(NOT CMAKE_CXX_STANDARD)
+    string(REGEX MATCH [=[..^]=] VAL "${PYBIND11_CPP_STANDARD}")
+    set(supported_standards 11 14 17 20)
+    if("${VAL}" IN_LIST supported_standards)
+      message(WARNING "USE -DCMAKE_CXX_STANDARD=${VAL} instead of PYBIND11_PYTHON_VERSION")
+      set(CMAKE_CXX_STANDARD ${VAL})
+    else()
+      message(FATAL_ERROR "PYBIND11_CPP_STANDARD should be replaced with CMAKE_CXX_STANDARD")
     endif()
+  endif()
 endif()
 
-
-
 # Checks whether the given CXX/linker flags can compile and link a cxx file.  cxxflags and
 # linkerflags are lists of flags to use.  The result variable is a unique variable name for each set
 # of flags: the compilation result will be cached base on the result variable.  If the flags work,
 # sets them in cxxflags_out/linkerflags_out internal cache variables (in addition to ${result}).
-function(_pybind11_return_if_cxx_and_linker_flags_work result cxxflags linkerflags cxxflags_out linkerflags_out)
+function(_pybind11_return_if_cxx_and_linker_flags_work result cxxflags linkerflags cxxflags_out
+         linkerflags_out)
   set(CMAKE_REQUIRED_LIBRARIES ${linkerflags})
   check_cxx_compiler_flag("${cxxflags}" ${result})
-  if (${result})
-    set(${cxxflags_out} "${cxxflags}" CACHE INTERNAL "" FORCE)
-    set(${linkerflags_out} "${linkerflags}" CACHE INTERNAL "" FORCE)
+  if(${result})
+    set(${cxxflags_out}
+        "${cxxflags}"
+        CACHE INTERNAL "" FORCE)
+    set(${linkerflags_out}
+        "${linkerflags}"
+        CACHE INTERNAL "" FORCE)
   endif()
 endfunction()
 
 # Internal: find the appropriate link time optimization flags for this compiler
 function(_pybind11_add_lto_flags target_name prefer_thin_lto)
-  if (NOT DEFINED PYBIND11_LTO_CXX_FLAGS)
-    set(PYBIND11_LTO_CXX_FLAGS "" CACHE INTERNAL "")
-    set(PYBIND11_LTO_LINKER_FLAGS "" CACHE INTERNAL "")
+  if(NOT DEFINED PYBIND11_LTO_CXX_FLAGS)
+    set(PYBIND11_LTO_CXX_FLAGS
+        ""
+        CACHE INTERNAL "")
+    set(PYBIND11_LTO_LINKER_FLAGS
+        ""
+        CACHE INTERNAL "")
 
     if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
       set(cxx_append "")
       set(linker_append "")
-      if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT APPLE)
+      if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND NOT APPLE)
         # Clang Gold plugin does not support -Os; append -O3 to MinSizeRel builds to override it
         set(linker_append ";$<$<CONFIG:MinSizeRel>:-O3>")
       elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
         set(cxx_append ";-fno-fat-lto-objects")
       endif()
 
-      if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND prefer_thin_lto)
-        _pybind11_return_if_cxx_and_linker_flags_work(HAS_FLTO_THIN
-          "-flto=thin${cxx_append}" "-flto=thin${linker_append}"
+      if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND prefer_thin_lto)
+        _pybind11_return_if_cxx_and_linker_flags_work(
+          HAS_FLTO_THIN "-flto=thin${cxx_append}" "-flto=thin${linker_append}"
           PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
       endif()
 
-      if (NOT HAS_FLTO_THIN)
-        _pybind11_return_if_cxx_and_linker_flags_work(HAS_FLTO
-          "-flto${cxx_append}" "-flto${linker_append}"
-          PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+      if(NOT HAS_FLTO_THIN)
+        _pybind11_return_if_cxx_and_linker_flags_work(
+          HAS_FLTO "-flto${cxx_append}" "-flto${linker_append}" PYBIND11_LTO_CXX_FLAGS
+          PYBIND11_LTO_LINKER_FLAGS)
       endif()
-    elseif (CMAKE_CXX_COMPILER_ID MATCHES "Intel")
+    elseif(CMAKE_CXX_COMPILER_ID MATCHES "Intel")
       # Intel equivalent to LTO is called IPO
-      _pybind11_return_if_cxx_and_linker_flags_work(HAS_INTEL_IPO
-      "-ipo" "-ipo" PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+      _pybind11_return_if_cxx_and_linker_flags_work(
+        HAS_INTEL_IPO "-ipo" "-ipo" PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
     elseif(MSVC)
       # cmake only interprets libraries as linker flags when they start with a - (otherwise it
       # converts /LTCG to \LTCG as if it was a Windows path).  Luckily MSVC supports passing flags
       # with - instead of /, even if it is a bit non-standard:
-      _pybind11_return_if_cxx_and_linker_flags_work(HAS_MSVC_GL_LTCG
-        "/GL" "-LTCG" PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
+      _pybind11_return_if_cxx_and_linker_flags_work(
+        HAS_MSVC_GL_LTCG "/GL" "-LTCG" PYBIND11_LTO_CXX_FLAGS PYBIND11_LTO_LINKER_FLAGS)
     endif()
 
-    if (PYBIND11_LTO_CXX_FLAGS)
+    if(PYBIND11_LTO_CXX_FLAGS)
       message(STATUS "LTO enabled")
     else()
       message(STATUS "LTO disabled (not supported by the compiler and/or linker)")
@@ -106,12 +114,13 @@ function(_pybind11_add_lto_flags target_name prefer_thin_lto)
   endif()
 
   # Enable LTO flags if found, except for Debug builds
-  if (PYBIND11_LTO_CXX_FLAGS)
+  if(PYBIND11_LTO_CXX_FLAGS)
     set(not_debug "$<NOT:$<CONFIG:Debug>>")
     set(cxx_lang "$<COMPILE_LANGUAGE:CXX>")
-    target_compile_options(${target_name} PRIVATE "$<$<AND:${not_debug},${cxx_lang}>:${PYBIND11_LTO_CXX_FLAGS}>")
+    target_compile_options(${target_name}
+                           PRIVATE "$<$<AND:${not_debug},${cxx_lang}>:${PYBIND11_LTO_CXX_FLAGS}>")
   endif()
-  if (PYBIND11_LTO_LINKER_FLAGS)
+  if(PYBIND11_LTO_LINKER_FLAGS)
     target_link_libraries(${target_name} PRIVATE "$<${not_debug}:${PYBIND11_LTO_LINKER_FLAGS}>")
   endif()
 endfunction()
@@ -143,7 +152,10 @@ function(pybind11_add_module target_name)
   target_link_libraries(${target_name} PRIVATE pybind11::module)
 
   if(ARG_SYSTEM)
-      message(STATUS "Warning: this does not have an effect - use NO_SYSTEM_FROM_IMPORTED if using imported targets")
+    message(
+      STATUS
+        "Warning: this does not have an effect - use NO_SYSTEM_FROM_IMPORTED if using imported targets"
+    )
   endif()
 
   # Python debug libraries expose slightly different objects before 3.8
@@ -165,35 +177,33 @@ function(pybind11_add_module target_name)
   set_target_properties(${target_name} PROPERTIES CXX_VISIBILITY_PRESET "hidden")
   set_target_properties(${target_name} PROPERTIES CUDA_VISIBILITY_PRESET "hidden")
 
-
   if(ARG_NO_EXTRAS)
-      return()
+    return()
   endif()
 
   if(CMAKE_VERSION VERSION_LESS 3.9 OR PYBIND11_CLASSIC_LTO)
-      _pybind11_add_lto_flags(${target_name} ${ARG_THIN_LTO})
+    _pybind11_add_lto_flags(${target_name} ${ARG_THIN_LTO})
   else()
-      include(CheckIPOSupported)
-      check_ipo_supported(RESULT supported OUTPUT error)
-      if(supported)
-          set_property(
-            TARGET
-              ${target_name}
-            PROPERTY
-              INTERPROCEDURAL_OPTIMIZATION TRUE
-            )
-      endif()
+    include(CheckIPOSupported)
+    check_ipo_supported(RESULT supported OUTPUT error)
+    if(supported)
+      set_property(TARGET ${target_name} PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
+    endif()
   endif()
 
-  if (NOT MSVC AND NOT ${CMAKE_BUILD_TYPE} MATCHES Debug|RelWithDebInfo)
+  if(NOT MSVC AND NOT ${CMAKE_BUILD_TYPE} MATCHES Debug|RelWithDebInfo)
     # Strip unnecessary sections of the binary on Linux/Mac OS
     if(CMAKE_STRIP)
       if(APPLE)
-        add_custom_command(TARGET ${target_name} POST_BUILD
-                           COMMAND ${CMAKE_STRIP} -x $<TARGET_FILE:${target_name}>)
+        add_custom_command(
+          TARGET ${target_name}
+          POST_BUILD
+          COMMAND ${CMAKE_STRIP} -x $<TARGET_FILE:${target_name}>)
       else()
-        add_custom_command(TARGET ${target_name} POST_BUILD
-                           COMMAND ${CMAKE_STRIP} $<TARGET_FILE:${target_name}>)
+        add_custom_command(
+          TARGET ${target_name}
+          POST_BUILD
+          COMMAND ${CMAKE_STRIP} $<TARGET_FILE:${target_name}>)
       endif()
     endif()
   endif()
@@ -209,7 +219,8 @@ function(pybind11_add_module target_name)
       # instance, projects that include other types of source files like CUDA
       # .cu files don't get these options propagated to nvcc since that would
       # cause the build to fail.
-      target_compile_options(${target_name} PRIVATE $<$<NOT:$<CONFIG:Debug>>:$<$<COMPILE_LANGUAGE:CXX>:/MP>>)
+      target_compile_options(${target_name}
+                             PRIVATE $<$<NOT:$<CONFIG:Debug>>:$<$<COMPILE_LANGUAGE:CXX>:/MP>>)
     endif()
   endif()
 endfunction()

From 6f6e9394ce37a737fab2a93248046dcccfa20da5 Mon Sep 17 00:00:00 2001
From: acxz <17132214+acxz@users.noreply.github.com>
Date: Thu, 30 Jul 2020 21:16:50 -0400
Subject: [PATCH 66/73] feat: add uninstall target for CMake (#2265)

* add uninstall target for cmake

* only add target when built as master project

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
---
 .gitignore                     |  1 -
 CMakeLists.txt                 |  9 +++++++++
 cmake/cmake_uninstall.cmake.in | 23 +++++++++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 cmake/cmake_uninstall.cmake.in

diff --git a/.gitignore b/.gitignore
index 4dca42ab7e..dbcc4784a6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -32,7 +32,6 @@ MANIFEST
 .DS_Store
 /dist
 /build
-/cmake/
 .cache/
 sosize-*.txt
 pybind11Config*.cmake
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 31e253f9dd..a9ab4fd2b6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -246,3 +246,12 @@ if(PYBIND11_INSTALL)
     NAMESPACE "pybind11::"
     DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
 endif()
+
+# Uninstall target
+if(PYBIND11_MASTER_PROJECT)
+  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/cmake/cmake_uninstall.cmake.in"
+                 "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake" IMMEDIATE @ONLY)
+
+  add_custom_target(uninstall COMMAND ${CMAKE_COMMAND} -P
+                                      ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
+endif()
diff --git a/cmake/cmake_uninstall.cmake.in b/cmake/cmake_uninstall.cmake.in
new file mode 100644
index 0000000000..53b16fb95e
--- /dev/null
+++ b/cmake/cmake_uninstall.cmake.in
@@ -0,0 +1,23 @@
+# Source: https://gitlab.kitware.com/cmake/community/-/wikis/FAQ#can-i-do-make-uninstall-with-cmake
+
+if(NOT EXISTS "@CMAKE_BINARY_DIR@/install_manifest.txt")
+  message(FATAL_ERROR "Cannot find install manifest: @CMAKE_BINARY_DIR@/install_manifest.txt")
+endif()
+
+file(READ "@CMAKE_BINARY_DIR@/install_manifest.txt" files)
+string(REGEX REPLACE "\n" ";" files "${files}")
+foreach(file ${files})
+  message(STATUS "Uninstalling $ENV{DESTDIR}${file}")
+  if(IS_SYMLINK "$ENV{DESTDIR}${file}" OR EXISTS "$ENV{DESTDIR}${file}")
+    exec_program(
+      "@CMAKE_COMMAND@" ARGS "-E remove \"$ENV{DESTDIR}${file}\""
+      OUTPUT_VARIABLE rm_out
+      RETURN_VALUE rm_retval
+      )
+    if(NOT "${rm_retval}" STREQUAL 0)
+      message(FATAL_ERROR "Problem when removing $ENV{DESTDIR}${file}")
+    endif()
+  else(IS_SYMLINK "$ENV{DESTDIR}${file}" OR EXISTS "$ENV{DESTDIR}${file}")
+    message(STATUS "File $ENV{DESTDIR}${file} does not exist.")
+  endif()
+endforeach()

From b8047245bbcc36c56d0be2103ca575b79c5e6a34 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <henry.fredrick.schreiner@cern.ch>
Date: Fri, 31 Jul 2020 04:16:40 -0400
Subject: [PATCH 67/73] fix: uninstall cleanup (#2346)

---
 .gitignore                                |  1 +
 CMakeLists.txt                            | 14 +++++++-------
 {cmake => tools}/cmake_uninstall.cmake.in |  0
 3 files changed, 8 insertions(+), 7 deletions(-)
 rename {cmake => tools}/cmake_uninstall.cmake.in (100%)

diff --git a/.gitignore b/.gitignore
index dbcc4784a6..54a1f92601 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@ CMakeCache.txt
 CMakeFiles
 Makefile
 cmake_install.cmake
+cmake_uninstall.cmake
 .DS_Store
 *.so
 *.pyd
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a9ab4fd2b6..6102ae4ebf 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -245,13 +245,13 @@ if(PYBIND11_INSTALL)
     EXPORT "${PYBIND11_EXPORT_NAME}"
     NAMESPACE "pybind11::"
     DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
-endif()
 
-# Uninstall target
-if(PYBIND11_MASTER_PROJECT)
-  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/cmake/cmake_uninstall.cmake.in"
-                 "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake" IMMEDIATE @ONLY)
+  # Uninstall target
+  if(PYBIND11_MASTER_PROJECT)
+    configure_file("${CMAKE_CURRENT_SOURCE_DIR}/tools/cmake_uninstall.cmake.in"
+                   "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake" IMMEDIATE @ONLY)
 
-  add_custom_target(uninstall COMMAND ${CMAKE_COMMAND} -P
-                                      ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
+    add_custom_target(uninstall COMMAND ${CMAKE_COMMAND} -P
+                                        ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
+  endif()
 endif()
diff --git a/cmake/cmake_uninstall.cmake.in b/tools/cmake_uninstall.cmake.in
similarity index 100%
rename from cmake/cmake_uninstall.cmake.in
rename to tools/cmake_uninstall.cmake.in

From 4d90f1a1998b394e075660fea1dbaf9d24ea0039 Mon Sep 17 00:00:00 2001
From: jbarlow83 <jbarlow83@users.noreply.github.com>
Date: Fri, 31 Jul 2020 17:46:12 -0700
Subject: [PATCH 68/73] Add error_scope to py::class_::dealloc() to protect
 destructor calls (#2342)

Fixes issue #1878
---
 include/pybind11/pybind11.h |  7 +++++++
 tests/test_class.cpp        | 11 +++++++++++
 tests/test_class.py         |  6 ++++++
 3 files changed, 24 insertions(+)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 87f4645e6a..d34c92c24a 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -1388,6 +1388,13 @@ class class_ : public detail::generic_type {
 
     /// Deallocates an instance; via holder, if constructed; otherwise via operator delete.
     static void dealloc(detail::value_and_holder &v_h) {
+        // We could be deallocating because we are cleaning up after a Python exception.
+        // If so, the Python error indicator will be set. We need to clear that before
+        // running the destructor, in case the destructor code calls more Python.
+        // If we don't, the Python API will exit with an exception, and pybind11 will
+        // throw error_already_set from the C++ destructor which is forbidden and triggers
+        // std::terminate().
+        error_scope scope;
         if (v_h.holder_constructed()) {
             v_h.holder<holder_type>().~holder_type();
             v_h.set_holder_constructed(false);
diff --git a/tests/test_class.cpp b/tests/test_class.cpp
index 7edcdce363..5369cb064c 100644
--- a/tests/test_class.cpp
+++ b/tests/test_class.cpp
@@ -379,6 +379,17 @@ TEST_SUBMODULE(class_, m) {
     // test_non_final_final
     struct IsNonFinalFinal {};
     py::class_<IsNonFinalFinal>(m, "IsNonFinalFinal", py::is_final());
+
+    struct PyPrintDestructor {
+        PyPrintDestructor() {}
+        ~PyPrintDestructor() {
+            py::print("Print from destructor");
+        }
+        void throw_something() { throw std::runtime_error("error"); }
+    };
+    py::class_<PyPrintDestructor>(m, "PyPrintDestructor")
+        .def(py::init<>())
+        .def("throw_something", &PyPrintDestructor::throw_something);
 }
 
 template <int N> class BreaksBase { public:
diff --git a/tests/test_class.py b/tests/test_class.py
index c38a5e8ce8..bbf8481a4d 100644
--- a/tests/test_class.py
+++ b/tests/test_class.py
@@ -323,3 +323,9 @@ def test_non_final_final():
         class PyNonFinalFinalChild(m.IsNonFinalFinal):
             pass
     assert str(exc_info.value).endswith("is not an acceptable base type")
+
+
+# https://github.com/pybind/pybind11/issues/1878
+def test_exception_rvalue_abort():
+    with pytest.raises(RuntimeError):
+        m.PyPrintDestructor().throw_something()

From 1caf1d0613c25817e6524286615f3d3cff34afb5 Mon Sep 17 00:00:00 2001
From: Henry Schreiner <HenrySchreinerIII@gmail.com>
Date: Sat, 1 Aug 2020 15:24:30 -0400
Subject: [PATCH 69/73] fix: check list validity and add missing file (#2352)

Added a check on CMake 3.12+ to make sure the file listing is up to date. And caught a missing file with it!
---
 CMakeLists.txt | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6102ae4ebf..7aa8ed72c9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -82,6 +82,7 @@ set(PYBIND11_HEADERS
     include/pybind11/eigen.h
     include/pybind11/embed.h
     include/pybind11/eval.h
+    include/pybind11/iostream.h
     include/pybind11/functional.h
     include/pybind11/numpy.h
     include/pybind11/operators.h
@@ -90,9 +91,26 @@ set(PYBIND11_HEADERS
     include/pybind11/stl.h
     include/pybind11/stl_bind.h)
 
-# TODO: compare with grep and warn if missmatched
+# Compare with grep and warn if mismatched
+if(PYBIND11_MASTER_PROJECT AND NOT CMAKE_VERSION VERSION_LESS 3.12)
+  file(
+    GLOB_RECURSE _pybind11_header_check
+    LIST_DIRECTORIES false
+    RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}"
+    CONFIGURE_DEPENDS "include/pybind11/*.h")
+  set(_pybind11_here_only ${PYBIND11_HEADERS})
+  set(_pybind11_disk_only ${_pybind11_header_check})
+  list(REMOVE_ITEM _pybind11_here_only ${_pybind11_header_check})
+  list(REMOVE_ITEM _pybind11_disk_only ${PYBIND11_HEADERS})
+  if(_pybind11_here_only)
+    message(AUTHOR_WARNING "PYBIND11_HEADERS has extra files:" ${_pybind11_here_only})
+  endif()
+  if(_pybind11_disk_only)
+    message(AUTHOR_WARNING "PYBIND11_HEADERS is missing files:" ${_pybind11_disk_only})
+  endif()
+endif()
 
-# cmake 3.12 added list(TRANSFORM <list> PREPEND
+# CMake 3.12 added list(TRANSFORM <list> PREPEND
 # But we can't use it yet
 string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/" PYBIND11_HEADERS
                "${PYBIND11_HEADERS}")

From 1ed85fdcab5d09e064aa2a05273eef0b5cb36ae6 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Mon, 3 Aug 2020 00:48:14 -0400
Subject: [PATCH 70/73] ci: Make drake-specific modifications

---
 .github/workflows/ci.yml | 137 ++++++++++++++++++++-------------------
 1 file changed, 69 insertions(+), 68 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2babc0d211..762fafca2f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,22 +7,23 @@ on:
     branches:
       - drake
 
-
 jobs:
   standard:
     strategy:
       fail-fast: false
       matrix:
-        runs-on: [ubuntu-latest, windows-latest, macos-latest]
+        # runs-on: [ubuntu-latest, windows-latest, macos-latest]
+        runs-on: [ubuntu-latest, macos-latest]
         arch: [x64]
         max-cxx-std: [17]
         python:
-        - 2.7
-        - 3.5
+        # - 2.7
+        # - 3.5
+        - 3.7
         - 3.8
         - 3.9-dev
-        - pypy2
-        - pypy3
+        # - pypy2
+        # - pypy3
 
         include:
           - runs-on: ubuntu-latest
@@ -33,21 +34,21 @@ jobs:
             python: 3.7
             arch: x64
             max-cxx-std: 17
-          - runs-on: windows-2016
-            python: 3.7
-            arch: x86
-            max-cxx-std: 14
+          # - runs-on: windows-2016
+          #   python: 3.7
+          #   arch: x86
+          #   max-cxx-std: 14
 
         exclude:
-            # Currently 32bit only, and we build 64bit
-          - runs-on: windows-latest
-            python: pypy2
-            arch: x64
-            max-cxx-std: 17
-          - runs-on: windows-latest
-            python: pypy3
-            arch: x64
-            max-cxx-std: 17
+          #   # Currently 32bit only, and we build 64bit
+          # - runs-on: windows-latest
+          #   python: pypy2
+          #   arch: x64
+          #   max-cxx-std: 17
+          # - runs-on: windows-latest
+          #   python: pypy3
+          #   arch: x64
+          #   max-cxx-std: 17
 
             # Currently can't build due to warning, fixed in CPython > 3.9b5
           - runs-on: macos-latest
@@ -55,15 +56,15 @@ jobs:
             arch: x64
             max-cxx-std: 17
 
-            # Currently broken on embed_test
-          - runs-on: windows-latest
-            python: 3.8
-            arch: x64
-            max-cxx-std: 17
-          - runs-on: windows-latest
-            python: 3.9-dev
-            arch: x64
-            max-cxx-std: 17
+          #   # Currently broken on embed_test
+          # - runs-on: windows-latest
+          #   python: 3.8
+          #   arch: x64
+          #   max-cxx-std: 17
+          # - runs-on: windows-latest
+          #   python: 3.9-dev
+          #   arch: x64
+          #   max-cxx-std: 17
 
     name: "🐍 ${{ matrix.python }} • ${{ matrix.runs-on }} • ${{ matrix.arch }}"
     runs-on: ${{ matrix.runs-on }}
@@ -141,11 +142,11 @@ jobs:
       fail-fast: false
       matrix:
         clang:
-          - 3.6
-          - 3.7
-          - 3.9
-          - 5
-          - 7
+          # - 3.6
+          # - 3.7
+          # - 3.9
+          # - 5
+          # - 7
           - 9
           - dev
 
@@ -225,51 +226,51 @@ jobs:
     - name: Interface test
       run: cmake --build build --target test_cmake_build
 
-  centos:
-    runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        centos:
-          - 7  # GCC 4.8
-          - 8
+  # centos:
+  #   runs-on: ubuntu-latest
+  #   strategy:
+  #     fail-fast: false
+  #     matrix:
+  #       centos:
+  #         - 7  # GCC 4.8
+  #         - 8
 
-    name: "🐍 3 • CentOS ${{ matrix.centos }} • x64"
-    container: "centos:${{ matrix.centos }}"
+  #   name: "🐍 3 • CentOS ${{ matrix.centos }} • x64"
+  #   container: "centos:${{ matrix.centos }}"
 
-    steps:
-    - uses: actions/checkout@v2
+  #   steps:
+  #   - uses: actions/checkout@v2
 
-    - name: Add Python 3
-      run: yum update -y && yum install -y python3-devel gcc-c++ make git
+  #   - name: Add Python 3
+  #     run: yum update -y && yum install -y python3-devel gcc-c++ make git
 
-    - name: Update pip
-      run: python3 -m pip install --upgrade pip
+  #   - name: Update pip
+  #     run: python3 -m pip install --upgrade pip
 
-    - name: Install dependencies
-      run: python3 -m pip install cmake -r tests/requirements.txt
+  #   - name: Install dependencies
+  #     run: python3 -m pip install cmake -r tests/requirements.txt
 
-    - name: Configure
-      shell: bash
-      run: >
-        cmake -S . -B build
-        -DPYBIND11_WERROR=ON
-        -DDOWNLOAD_CATCH=ON
-        -DDOWNLOAD_EIGEN=ON
-        -DCMAKE_CXX_STANDARD=11
-        -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
+  #   - name: Configure
+  #     shell: bash
+  #     run: >
+  #       cmake -S . -B build
+  #       -DPYBIND11_WERROR=ON
+  #       -DDOWNLOAD_CATCH=ON
+  #       -DDOWNLOAD_EIGEN=ON
+  #       -DCMAKE_CXX_STANDARD=11
+  #       -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)")
 
-    - name: Build
-      run: cmake --build build -j 2
+  #   - name: Build
+  #     run: cmake --build build -j 2
 
-    - name: Python tests
-      run: cmake --build build --target pytest
+  #   - name: Python tests
+  #     run: cmake --build build --target pytest
 
-    - name: C++ tests
-      run: cmake --build build --target cpptest
+  #   - name: C++ tests
+  #     run: cmake --build build --target cpptest
 
-    - name: Interface test
-      run: cmake --build build --target test_cmake_build
+  #   - name: Interface test
+  #     run: cmake --build build --target test_cmake_build
 
   install-classic:
     name: "🐍 3.5 • Debian • x86 •  Install"

From 6e8628e090e43873fed384afc8a2e733f823d2aa Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Mon, 3 Aug 2020 01:03:38 -0400
Subject: [PATCH 71/73] drake: Remove redundant cast(T&&) overloads

They cause errors otherwise
---
 include/pybind11/cast.h | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/include/pybind11/cast.h b/include/pybind11/cast.h
index 1d31233c73..7a073d552f 100644
--- a/include/pybind11/cast.h
+++ b/include/pybind11/cast.h
@@ -2040,14 +2040,6 @@ detail::enable_if_t<
         detail::make_caster<T>::cast(std::move(value), return_value_policy::take_ownership, no_parent));
 }
 
-template <typename T>
-detail::enable_if_t<
-        std::is_rvalue_reference<T&&>::value && !std::is_pointer<T>::value && !detail::is_pyobject<detail::intrinsic_t<T>>::value, object>
-    cast(T&& value) {
-    // Have to use `pybind11::move` because some compilers might try to bind `move` to `std::move`...
-    return pybind11::move<T>(std::move(value));
-}
-
 template <typename T>
 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     if (obj.ref_count() > 1)

From 5258a6904fea7fab924e6997a62106033ad43855 Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Sun, 6 Sep 2020 12:38:42 -0400
Subject: [PATCH 72/73] Fix formatting errors

---
 docs/advanced/classes.rst        | 4 ++--
 tests/CMakeLists.txt             | 2 +-
 tests/test_ownership_transfer.py | 1 +
 tests/test_smart_ptr.py          | 7 ++++---
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/docs/advanced/classes.rst b/docs/advanced/classes.rst
index c04b5fc43a..b2d963dc4f 100644
--- a/docs/advanced/classes.rst
+++ b/docs/advanced/classes.rst
@@ -1312,7 +1312,7 @@ Normally, if you keep the object alive in Python, then no additional instrumenta
     >>> cat = Cat()
     >>> c.add(cat)  # This object lives in both Python and C++.
     >>> c.release().go(2)
-    meow! meow! 
+    meow! meow!
 
 However, if you pass an instance that Python later wishes to destroy, without :class:`py::wrapper`, we would get an error that ``go`` is not implented,
 as the `Cat` portion would have been destroyed and no longer visible for the trampoline. With the wrapper, ``pybind11`` will intercept this event and keep the Python portion alive:
@@ -1321,6 +1321,6 @@ as the `Cat` portion would have been destroyed and no longer visible for the tra
 
     >>> c.add(Cat())
     >>> c.release().go(2)
-    meow! meow! 
+    meow! meow!
 
 Note that both the C++ and Python portion of ``cat`` will be destroyed once ``cage`` is destroyed.
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 2f5403dd57..a7a9d94078 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -69,7 +69,7 @@ set(PYBIND11_TEST_FILES
     test_numpy_vectorize.cpp
     test_opaque_types.cpp
     test_operator_overloading.cpp
-  test_ownership_transfer.cpp
+    test_ownership_transfer.cpp
     test_pickling.cpp
     test_pytypes.cpp
     test_sequences_and_iterators.cpp
diff --git a/tests/test_ownership_transfer.py b/tests/test_ownership_transfer.py
index 49c2814df1..c8a6edfe91 100644
--- a/tests/test_ownership_transfer.py
+++ b/tests/test_ownership_transfer.py
@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 from pybind11_tests import ownership_transfer as m
 from pybind11_tests import ConstructorStats
 
diff --git a/tests/test_smart_ptr.py b/tests/test_smart_ptr.py
index f85152234e..8c97e5ab90 100644
--- a/tests/test_smart_ptr.py
+++ b/tests/test_smart_ptr.py
@@ -295,14 +295,15 @@ def test_unique_ptr_arg():
 
     pass_through_list = [
         m.unique_ptr_pass_through,
-        m.unique_ptr_pass_through_cast_from_py,
-        m.unique_ptr_pass_through_move_from_py,
         m.unique_ptr_pass_through_move_to_py,
         m.unique_ptr_pass_through_cast_to_py,
+        # TODO(eric.cousineau): Fix these cases.
+        # m.unique_ptr_pass_through_cast_from_py,
+        # m.unique_ptr_pass_through_move_from_py,
     ]
     for pass_through in pass_through_list:
         obj = m.UniquePtrHeld(1)
-        obj_ref = m.unique_ptr_pass_through(obj)
+        obj_ref = pass_through(obj)
         assert stats.alive() == 1
         assert obj.value() == 1
         assert obj == obj_ref

From 2211d5022f6db161e7947a39fe4497e7df9734df Mon Sep 17 00:00:00 2001
From: Eric Cousineau <eric.cousineau@tri.global>
Date: Sun, 6 Sep 2020 13:00:27 -0400
Subject: [PATCH 73/73] README_DRAKE: Update CI information

---
 README_DRAKE.md | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/README_DRAKE.md b/README_DRAKE.md
index 2011b841b3..1cde820bb7 100644
--- a/README_DRAKE.md
+++ b/README_DRAKE.md
@@ -40,28 +40,28 @@ source code (e.g. no whitespace reflowing), and try to stay relatively close to
 
 ## Continuous Integration
 
-For simplicity, these checks are copied from upstream's CI which uses Travis
-CI as part of GitHub's Checks. They test:
+For simplicity, these checks are copied from upstream's CI which uses GitHub
+Actions as part of GitHub's checks. They test:
 
-* Ubuntu and macOS (Windows tests disabled)
-* C++11, C++14, and C++17
+* Code formatting (Python, C++, CMake)
+* Latest Ubuntu and macOS images
+    * **drake specific**: Windows and centOS disabled
+* C++11 and C++17
 * Release and debug builds
-* GCC 4.8, 6, and 7
-* clang 7
-* Apple clang 7.3 and 9
-* 64bit and 32bit
-* CPython and PyPy (though PyPy is partially supported on this fork)
-* Python 2.7, 3.5, 3.6, 3.7, and 3.8
-
-To see builds, see [this fork's Travis CI page](https://travis-ci.com/RobotLocomotion/pybind11/branches).
-
-Windows testing (with AppVeyor) is disabled for this repository.
+* GCC and clang
+* 64bit
+    * **drake specific**: no 32bit since Windows is disabled
+* CPython
+    * **drake difference**: PyPy is disabled
+* Python 3.6, 3.7, and 3.8
+    * **drake difference**: Python 2.7 and 3.5 are disabled
 
 ### Quick Testing
 
+For quickly testing Drake modifications on the platform's Python 3 interpreter:
+
     mkdir build && cd build
     cmake .. \
-        -DPYTHON_EXECUTABLE=$(which python3) \
         -DPYBIND11_TEST_OVERRIDE='test_builtin_casters.cpp;test_class.cpp;test_eigen.cpp;test_multiple_inheritance.cpp;test_ownership_transfer.cpp;test_smart_ptr.cpp'
     make -j 4 pytest