Use sizeof(long double) == sizeof(double) instead of std::is_same<>

Author: rwgk

tests/test_buffers.cpp

@@ -14,7 +14,7 @@
 #include "pybind11_tests.h"
 
 TEST_SUBMODULE(buffers, m) {
-    m.attr("std_is_same_double_long_double") = std::is_same<double, long double>::value;
+    m.attr("long_double_and_double_have_same_size") = (sizeof(long double) == sizeof(double));
 
     m.def("format_descriptor_format_buffer_info_compare",
           [](const std::string &cpp_name, const py::buffer &buffer) {

tests/test_buffers.py

@@ -10,7 +10,7 @@
 
 np = pytest.importorskip("numpy")
 
-if m.std_is_same_double_long_double:  # Windows.
+if m.long_double_and_double_have_same_size:  # Windows.
     np_float128 = None
     np_complex256 = None
 else: