refactor: drop Python 2 C++ code

Author: henryiii

docs/Doxyfile

@@ -18,5 +18,4 @@ ALIASES               += "endrst=\endverbatim"
 QUIET                  = YES
 WARNINGS               = YES
 WARN_IF_UNDOCUMENTED   = NO
-PREDEFINED             = PY_MAJOR_VERSION=3 \
-                         PYBIND11_NOINLINE
+PREDEFINED             = PYBIND11_NOINLINE

include/pybind11/cast.h

@@ -375,36 +375,15 @@ struct string_caster {
     static constexpr size_t UTF_N = 8 * sizeof(CharT);
 
     bool load(handle src, bool) {
-#if PY_MAJOR_VERSION < 3
-        object temp;
-#endif
         handle load_src = src;
         if (!src) {
             return false;
         }
         if (!PyUnicode_Check(load_src.ptr())) {
-#if PY_MAJOR_VERSION >= 3
             return load_bytes(load_src);
-#else
-            if (std::is_same<CharT, char>::value) {
-                return load_bytes(load_src);
-            }
-
-            // The below is a guaranteed failure in Python 3 when PyUnicode_Check returns false
-            if (!PYBIND11_BYTES_CHECK(load_src.ptr()))
-                return false;
-
-            temp = reinterpret_steal<object>(PyUnicode_FromObject(load_src.ptr()));
-            if (!temp) {
-                PyErr_Clear();
-                return false;
-            }
-            load_src = temp;
-#endif
         }
 
-#if PY_VERSION_HEX >= 0x03030000
-        // On Python >= 3.3, for UTF-8 we avoid the need for a temporary `bytes`
+        // On Python 3.3, for UTF-8 we avoid the need for a temporary `bytes`
         // object by using `PyUnicode_AsUTF8AndSize`.
         if (PYBIND11_SILENCE_MSVC_C4127(UTF_N == 8)) {
             Py_ssize_t size = -1;
@@ -417,7 +396,6 @@ struct string_caster {
             value = StringType(buffer, static_cast<size_t>(size));
             return true;
         }
-#endif
 
         auto utfNbytes
             = reinterpret_steal<object>(PyUnicode_AsEncodedString(load_src.ptr(),
@@ -922,18 +900,6 @@ struct pyobject_caster {
 
     template <typename T = type, enable_if_t<std::is_base_of<object, T>::value, int> = 0>
     bool load(handle src, bool /* convert */) {
-#if PY_MAJOR_VERSION < 3 && !defined(PYBIND11_STR_LEGACY_PERMISSIVE)
-        // For Python 2, without this implicit conversion, Python code would
-        // need to be cluttered with six.ensure_text() or similar, only to be
-        // un-cluttered later after Python 2 support is dropped.
-        if (PYBIND11_SILENCE_MSVC_C4127(std::is_same<T, str>::value) && isinstance<bytes>(src)) {
-            PyObject *str_from_bytes = PyUnicode_FromEncodedObject(src.ptr(), "utf-8", nullptr);
-            if (!str_from_bytes)
-                throw error_already_set();
-            value = reinterpret_steal<type>(str_from_bytes);
-            return true;
-        }
-#endif
         if (!isinstance<type>(src)) {
             return false;
         }

include/pybind11/detail/class.h

@@ -15,12 +15,12 @@
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
-#if PY_VERSION_HEX >= 0x03030000 && !defined(PYPY_VERSION)
+#if !defined(PYPY_VERSION)
 #    define PYBIND11_BUILTIN_QUALNAME
 #    define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)
 #else
-// In pre-3.3 Python, we still set __qualname__ so that we can produce reliable function type
-// signatures; in 3.3+ this macro expands to nothing:
+// In PyPy, we still set __qualname__ so that we can produce reliable function type
+// signatures; in CPython this macro expands to nothing:
 #    define PYBIND11_SET_OLDPY_QUALNAME(obj, nameobj)                                             \
         setattr((PyObject *) obj, "__qualname__", nameobj)
 #endif
@@ -155,7 +155,6 @@ extern "C" inline int pybind11_meta_setattro(PyObject *obj, PyObject *name, PyOb
     }
 }
 
-#if PY_MAJOR_VERSION >= 3
 /**
  * Python 3's PyInstanceMethod_Type hides itself via its tp_descr_get, which prevents aliasing
  * methods via cls.attr("m2") = cls.attr("m1"): instead the tp_descr_get returns a plain function,
@@ -170,7 +169,6 @@ extern "C" inline PyObject *pybind11_meta_getattro(PyObject *obj, PyObject *name
     }
     return PyType_Type.tp_getattro(obj, 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) {
@@ -266,9 +264,7 @@ inline PyTypeObject *make_default_metaclass() {
     type->tp_call = pybind11_meta_call;
 
     type->tp_setattro = pybind11_meta_setattro;
-#if PY_MAJOR_VERSION >= 3
     type->tp_getattro = pybind11_meta_getattro;
-#endif
 
     type->tp_dealloc = pybind11_meta_dealloc;
 
@@ -613,9 +609,6 @@ extern "C" inline void pybind11_releasebuffer(PyObject *, Py_buffer *view) {
 /// Give this type a buffer interface.
 inline void enable_buffer_protocol(PyHeapTypeObject *heap_type) {
     heap_type->ht_type.tp_as_buffer = &heap_type->as_buffer;
-#if PY_MAJOR_VERSION < 3
-    heap_type->ht_type.tp_flags |= Py_TPFLAGS_HAVE_NEWBUFFER;
-#endif
 
     heap_type->as_buffer.bf_getbuffer = pybind11_getbuffer;
     heap_type->as_buffer.bf_releasebuffer = pybind11_releasebuffer;
@@ -628,12 +621,8 @@ inline PyObject *make_new_python_type(const type_record &rec) {
 
     auto qualname = name;
     if (rec.scope && !PyModule_Check(rec.scope.ptr()) && hasattr(rec.scope, "__qualname__")) {
-#if PY_MAJOR_VERSION >= 3
         qualname = reinterpret_steal<object>(
             PyUnicode_FromFormat("%U.%U", rec.scope.attr("__qualname__").ptr(), name.ptr()));
-#else
-        qualname = str(rec.scope.attr("__qualname__").cast<std::string>() + "." + rec.name);
-#endif
     }
 
     object module_;
@@ -697,15 +686,10 @@ inline PyObject *make_new_python_type(const type_record &rec) {
     type->tp_as_number = &heap_type->as_number;
     type->tp_as_sequence = &heap_type->as_sequence;
     type->tp_as_mapping = &heap_type->as_mapping;
-#if PY_VERSION_HEX >= 0x03050000
     type->tp_as_async = &heap_type->as_async;
-#endif
 
     /* Flags */
     type->tp_flags |= Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HEAPTYPE;
-#if PY_MAJOR_VERSION < 3
-    type->tp_flags |= Py_TPFLAGS_CHECKTYPES;
-#endif
     if (!rec.is_final) {
         type->tp_flags |= Py_TPFLAGS_BASETYPE;
     }

include/pybind11/detail/common.h

@@ -273,65 +273,33 @@
 //               the transition from the legacy behavior to the non-permissive
 //               behavior.
 
-#if PY_MAJOR_VERSION >= 3 /// Compatibility macros for various Python versions
-#    define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
-#    define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
-#    define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
-#    define PYBIND11_BYTES_CHECK PyBytes_Check
-#    define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
-#    define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
-#    define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
-#    define PYBIND11_BYTES_AS_STRING PyBytes_AsString
-#    define PYBIND11_BYTES_SIZE PyBytes_Size
-#    define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
-#    define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
-#    define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
-#    define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
-#    define PYBIND11_BYTES_NAME "bytes"
-#    define PYBIND11_STRING_NAME "str"
-#    define PYBIND11_SLICE_OBJECT PyObject
-#    define PYBIND11_FROM_STRING PyUnicode_FromString
-#    define PYBIND11_STR_TYPE ::pybind11::str
-#    define PYBIND11_BOOL_ATTR "__bool__"
-#    define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
-#    define PYBIND11_BUILTINS_MODULE "builtins"
+/// Compatibility macros for Python 2 / Python 3 versions TODO: remove
+#define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
+#define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
+#define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
+#define PYBIND11_BYTES_CHECK PyBytes_Check
+#define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
+#define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
+#define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
+#define PYBIND11_BYTES_AS_STRING PyBytes_AsString
+#define PYBIND11_BYTES_SIZE PyBytes_Size
+#define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
+#define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
+#define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) (o))
+#define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) (o))
+#define PYBIND11_BYTES_NAME "bytes"
+#define PYBIND11_STRING_NAME "str"
+#define PYBIND11_SLICE_OBJECT PyObject
+#define PYBIND11_FROM_STRING PyUnicode_FromString
+#define PYBIND11_STR_TYPE ::pybind11::str
+#define PYBIND11_BOOL_ATTR "__bool__"
+#define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
+#define PYBIND11_BUILTINS_MODULE "builtins"
 // Providing a separate declaration to make Clang's -Wmissing-prototypes happy.
 // See comment for PYBIND11_MODULE below for why this is marked "maybe unused".
-#    define PYBIND11_PLUGIN_IMPL(name)                                                            \
-        extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name();               \
-        extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
-
-#else
-#    define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyMethod_New(ptr, nullptr, class_)
-#    define PYBIND11_INSTANCE_METHOD_CHECK PyMethod_Check
-#    define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyMethod_GET_FUNCTION
-#    define PYBIND11_BYTES_CHECK PyString_Check
-#    define PYBIND11_BYTES_FROM_STRING PyString_FromString
-#    define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyString_FromStringAndSize
-#    define PYBIND11_BYTES_AS_STRING_AND_SIZE PyString_AsStringAndSize
-#    define PYBIND11_BYTES_AS_STRING PyString_AsString
-#    define PYBIND11_BYTES_SIZE PyString_Size
-#    define PYBIND11_LONG_CHECK(o) (PyInt_Check(o) || PyLong_Check(o))
-#    define PYBIND11_LONG_AS_LONGLONG(o)                                                          \
-        (PyInt_Check(o) ? (long long) PyLong_AsLong(o) : PyLong_AsLongLong(o))
-#    define PYBIND11_LONG_FROM_SIGNED(o) PyInt_FromSsize_t((ssize_t) o) // Returns long if needed.
-#    define PYBIND11_LONG_FROM_UNSIGNED(o) PyInt_FromSize_t((size_t) o) // Returns long if needed.
-#    define PYBIND11_BYTES_NAME "str"
-#    define PYBIND11_STRING_NAME "unicode"
-#    define PYBIND11_SLICE_OBJECT PySliceObject
-#    define PYBIND11_FROM_STRING PyString_FromString
-#    define PYBIND11_STR_TYPE ::pybind11::bytes
-#    define PYBIND11_BOOL_ATTR "__nonzero__"
-#    define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_nonzero)
-#    define PYBIND11_BUILTINS_MODULE "__builtin__"
-// Providing a separate PyInit decl to make Clang's -Wmissing-prototypes happy.
-// See comment for PYBIND11_MODULE below for why this is marked "maybe unused".
-#    define PYBIND11_PLUGIN_IMPL(name)                                                            \
-        static PyObject *pybind11_init_wrapper();                                                 \
-        extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT void init##name();                       \
-        extern "C" PYBIND11_EXPORT void init##name() { (void) pybind11_init_wrapper(); }          \
-        PyObject *pybind11_init_wrapper()
-#endif
+#define PYBIND11_PLUGIN_IMPL(name)                                                                \
+    extern "C" PYBIND11_MAYBE_UNUSED PYBIND11_EXPORT PyObject *PyInit_##name();                   \
+    extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
 
 #if PY_VERSION_HEX >= 0x03050000 && PY_VERSION_HEX < 0x03050200
 extern "C" {
@@ -365,31 +333,15 @@ PyAPI_DATA(_Py_atomic_address) _PyThreadState_Current;
         }                                                                                         \
     }
 
-#if PY_VERSION_HEX >= 0x03030000
-
-#    define PYBIND11_CATCH_INIT_EXCEPTIONS                                                        \
-        catch (pybind11::error_already_set & e) {                                                 \
-            pybind11::raise_from(e, PyExc_ImportError, "initialization failed");                  \
-            return nullptr;                                                                       \
-        }                                                                                         \
-        catch (const std::exception &e) {                                                         \
-            PyErr_SetString(PyExc_ImportError, e.what());                                         \
-            return nullptr;                                                                       \
-        }
-
-#else
-
-#    define PYBIND11_CATCH_INIT_EXCEPTIONS                                                        \
-        catch (pybind11::error_already_set & e) {                                                 \
-            PyErr_SetString(PyExc_ImportError, e.what());                                         \
-            return nullptr;                                                                       \
-        }                                                                                         \
-        catch (const std::exception &e) {                                                         \
-            PyErr_SetString(PyExc_ImportError, e.what());                                         \
-            return nullptr;                                                                       \
-        }
-
-#endif
+#define PYBIND11_CATCH_INIT_EXCEPTIONS                                                            \
+    catch (pybind11::error_already_set & e) {                                                     \
+        pybind11::raise_from(e, PyExc_ImportError, "initialization failed");                      \
+        return nullptr;                                                                           \
+    }                                                                                             \
+    catch (const std::exception &e) {                                                             \
+        PyErr_SetString(PyExc_ImportError, e.what());                                             \
+        return nullptr;                                                                           \
+    }
 
 /** \rst
     ***Deprecated in favor of PYBIND11_MODULE***

include/pybind11/detail/internals.h

@@ -82,7 +82,7 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 #    define PYBIND11_TLS_KEY_INIT(var) PYBIND11_TLS_KEY_REF var = 0;
 #    define PYBIND11_TLS_KEY_CREATE(var) (((var) = PyThread_create_key()) != -1)
 #    define PYBIND11_TLS_GET_VALUE(key) PyThread_get_key_value((key))
-#    if PY_MAJOR_VERSION < 3 || defined(PYPY_VERSION)
+#    if defined(PYPY_VERSION)
 // On CPython < 3.4 and on PyPy, `PyThread_set_key_value` strangely does not set
 // the value if it has already been set.  Instead, it must first be deleted and
 // then set again.
@@ -294,7 +294,6 @@ inline internals **&get_internals_pp() {
     return internals_pp;
 }
 
-#if PY_VERSION_HEX >= 0x03030000
 // forward decl
 inline void translate_exception(std::exception_ptr);
 
@@ -318,21 +317,11 @@ bool handle_nested_exception(const T &exc, const std::exception_ptr &p) {
     return false;
 }
 
-#else
-
-template <class T>
-bool handle_nested_exception(const T &, std::exception_ptr &) {
-    return false;
-}
-#endif
-
 inline bool raise_err(PyObject *exc_type, const char *msg) {
-#if PY_VERSION_HEX >= 0x03030000
     if (PyErr_Occurred()) {
         raise_from(exc_type, msg);
         return true;
     }
-#endif
     PyErr_SetString(exc_type, msg);
     return false;
 }

include/pybind11/detail/type_caster_base.h

@@ -443,17 +443,10 @@ PYBIND11_NOINLINE void instance::allocate_layout() {
         // they default to using pymalloc, which is designed to be efficient for small allocations
         // like the one we're doing here; in earlier versions (and for larger allocations) they are
         // just wrappers around malloc.
-#if PY_VERSION_HEX >= 0x03050000
         nonsimple.values_and_holders = (void **) PyMem_Calloc(space, sizeof(void *));
         if (!nonsimple.values_and_holders) {
             throw std::bad_alloc();
         }
-#else
-        nonsimple.values_and_holders = (void **) PyMem_New(void *, space);
-        if (!nonsimple.values_and_holders)
-            throw std::bad_alloc();
-        std::memset(nonsimple.values_and_holders, 0, space * sizeof(void *));
-#endif
         nonsimple.status
             = reinterpret_cast<std::uint8_t *>(&nonsimple.values_and_holders[flags_at]);
     }
@@ -494,11 +487,9 @@ PYBIND11_NOINLINE std::string error_string() {
 
     PyErr_NormalizeException(&scope.type, &scope.value, &scope.trace);
 
-#if PY_MAJOR_VERSION >= 3
     if (scope.trace != nullptr) {
         PyException_SetTraceback(scope.value, scope.trace);
     }
-#endif
 
 #if !defined(PYPY_VERSION)
     if (scope.trace) {
@@ -547,10 +538,6 @@ PYBIND11_NOINLINE handle get_object_handle(const void *ptr, const detail::type_i
 inline PyThreadState *get_thread_state_unchecked() {
 #if defined(PYPY_VERSION)
     return PyThreadState_GET();
-#elif PY_VERSION_HEX < 0x03000000
-    return _PyThreadState_Current;
-#elif PY_VERSION_HEX < 0x03050000
-    return (PyThreadState *) _Py_atomic_load_relaxed(&_PyThreadState_Current);
 #elif PY_VERSION_HEX < 0x03050200
     return (PyThreadState *) _PyThreadState_Current.value;
 #else