[vstinner]

Add __extension__ on the PyObject inner struct to fix the g++ warning:

Include/object.h:131:16: error: ISO C++ prohibits anonymous
structs [-Wpedantic]
131 |         struct {

• Issue: object.h:131:16: error: ISO C++ prohibits anonymous structs [-Wpedantic] #160208

[vstinner]

Tests / Windows (free-threading) / Build and test (x64, switch-case) (pull_request): Failing after 35m

It's likely a flaky test:

FAIL: test_release_task_refs (test.test_multiprocessing_spawn.test_processes.WithProcessesTestPool.test_release_task_refs)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\a\cpython\cpython\Lib\test\_test_multiprocessing.py", line 3443, in test_release_task_refs
    self.assertEqual(CountedObject.n_instances, 0)
    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 4 != 0

[vstinner]

The change should be backported manually to 3.14 which doesn't have _Py_ANONYMOUS macro. Maybe this macro should be backported to 3.14 as well.

[vstinner]

@mtelka: Would you be able to test this fix?

[mtelka]

@mtelka: Would you be able to test this fix?

  building '_test_cppext' extension
  creating build/temp.solaris-2.11-i86pc.64bit-cpython-315
  /usr/gcc/14/bin/g++ -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -fno-strict-overflow -Wsign-compare -DNDEBUG -g -O3 -Wall -m64 -O3 -g -gdwarf-4 -gstrict-dwarf -msave-args -fno-reorder-functions -fno-reorder-blocks-and-partition -D_XOPEN_SOURCE=600 -D__EXTENSIONS__=1 -D_XPG6 -D_REENTRANT -fPIC -I/data/builds/oi-py315/components/python/python-315/build/amd64/build/test_python_199041æ/tempcwd/env/include -I/data/builds/oi-py315/components/python/python-315/Python-3.15.1/Include -I/data/builds/oi-py315/components/python/python-315/build/amd64 -c extension.cpp -o build/temp.solaris-2.11-i86pc.64bit-cpython-315/extension.o -Wall -Wextra -Werror -DMODULE_NAME=_test_cppext -pedantic-errors -Wno-long-long
  In file included from /data/builds/oi-py315/components/python/python-315/Python-3.15.1/Include/Python.h:79,
                   from extension.c:16,
                   from extension.cpp:3:
  /data/builds/oi-py315/components/python/python-315/Python-3.15.1/Include/object.h:131:30: error: ISO C++ prohibits anonymous structs [-Wpedantic]
    131 |         _Py_ANONYMOUS struct {
        |                              ^
  error: command '/usr/gcc/14/bin/g++' failed with exit code 1
  error: subprocess-exited-with-error

  × Building wheel for internal__test_cppext (pyproject.toml) did not run successfully.
  │ exit code: 1
  ╰─> No available output.

  note: This error originates from a subprocess, and is likely not a problem with pip.

[mtelka]

Looking at the _Py_ANONYMOUS macro I think it is obvious that this is not the way to go.

cpython/Include/pymacro.h

Lines 90 to 108 in 784b305

	// _Py_ANONYMOUS: modifier for declaring an anonymous union.
	// Usage: _Py_ANONYMOUS union { ... };
	// Standards/compiler support:
	// - C++ allows anonymous unions, but not structs
	// - C11 and above allows anonymous unions and structs
	// - MSVC has warning(disable: 4201) "nonstandard extension used : nameless
	// struct/union". This is specific enough that we disable it for all of
	// Python.h.
	// - GCC & clang needs __extension__ before C11
	// To allow unsupported platforms which need other spellings, we use a
	// predefined value of _Py_ANONYMOUS if it exists.
	#ifndef _Py_ANONYMOUS
	# if (defined(__GNUC__) || defined(__clang__)) \
	&& !(defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L)
	# define _Py_ANONYMOUS __extension__
	# else
	# define _Py_ANONYMOUS
	# endif
	#endif

[vstinner]

Ok, so this change doesn't work. I wrote a different fix: #160332.