Narrow down the scope of -Wstrict-aliasing

Author: bstaletic

include/pybind11/pybind11.h

@@ -10,14 +10,6 @@
 
 #pragma once
 
-#if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
-#  define PYBIND11_STD_LAUNDER std::launder
-#  define PYBIND11_HAS_STD_LAUNDER 1
-#else
-#  define PYBIND11_STD_LAUNDER
-#  define PYBIND11_HAS_STD_LAUNDER 0
-#endif
-
 #if defined(__INTEL_COMPILER)
 #  pragma warning push
 #  pragma warning disable 68    // integer conversion resulted in a change of sign
@@ -43,9 +35,6 @@
 #  pragma GCC diagnostic ignored "-Wunused-but-set-parameter"
 #  pragma GCC diagnostic ignored "-Wunused-but-set-variable"
 #  pragma GCC diagnostic ignored "-Wmissing-field-initializers"
-#  if !PYBIND11_HAS_STD_LAUNDER
-#    pragma GCC diagnostic ignored "-Wstrict-aliasing"
-#  endif
 #  pragma GCC diagnostic ignored "-Wattributes"
 #  if __GNUC__ >= 7
 #    pragma GCC diagnostic ignored "-Wnoexcept-type"
@@ -63,6 +52,13 @@
 #include <string>
 #include <utility>
 
+#if defined(__cpp_lib_launder) && !(defined(_MSC_VER) && (_MSC_VER < 1914))
+#  define PYBIND11_STD_LAUNDER std::launder
+#  define PYBIND11_HAS_STD_LAUNDER 1
+#else
+#  define PYBIND11_STD_LAUNDER
+#  define PYBIND11_HAS_STD_LAUNDER 0
+#endif
 #if defined(__GNUG__) && !defined(__clang__)
 #  include <cxxabi.h>
 #endif
@@ -161,8 +157,20 @@ class cpp_function : public function {
 #if defined(__GNUG__) && !defined(__clang__) && __GNUC__ >= 6
 #  pragma GCC diagnostic pop
 #endif
+#if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif
+            // UB without std::launder, but without breaking ABI and/or
+            // a significant refactoring it's "impossible" to solve'
             if (!std::is_trivially_destructible<Func>::value)
-                rec->free_data = [](function_record *r) { PYBIND11_STD_LAUNDER((capture *) &r->data)->~capture(); };
+                rec->free_data = [](function_record *r) {
+                    auto data = PYBIND11_STD_LAUNDER((capture *) &r->data);
+                    data->~capture();
+                };
+#if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER
+#  pragma GCC diagnostic pop
+#endif
         } else {
             rec->data[0] = new capture { std::forward<Func>(f) };
             rec->free_data = [](function_record *r) { delete ((capture *) r->data[0]); };