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gh-154643: Only use _Py_STDC_VERSION when defined #154650

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gh-154643: Only use _Py_STDC_VERSION when defined #154650

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2363a51
gh-154643: Only use _Py_STDC_VERSION when defined
hroncok Jul 24, 2026
e81f0f6
Also add test for C
hroncok Nov 6, 2026
f29d610
Add -Werror=undef to PUBLIC_CFLAGS & PEDANTIC_CXXFLAGS in setup.py
hroncok Nov 6, 2026
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2 changes: 1 addition & 1 deletion Include/cpython/pyatomic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -585,7 +585,7 @@ static inline void _Py_atomic_fence_release(void);
# define Py_ATOMIC_GCC_H
# include "pyatomic_gcc.h"
# undef Py_ATOMIC_GCC_H
#elif _Py_STDC_VERSION >= 201112L && !defined(__STDC_NO_ATOMICS__)
#elif defined(_Py_STDC_VERSION) && _Py_STDC_VERSION >= 201112L && !defined(__STDC_NO_ATOMICS__)
# define Py_ATOMIC_STD_H
# include "pyatomic_std.h"
# undef Py_ATOMIC_STD_H
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2 changes: 1 addition & 1 deletion Include/pyport.h
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Expand Up @@ -491,7 +491,7 @@ extern "C" {
#ifdef WITH_THREAD
# ifdef thread_local
# define _Py_thread_local thread_local
# elif _Py_STDC_VERSION >= 201112L && !defined(__STDC_NO_THREADS__)
# elif defined(_Py_STDC_VERSION) && _Py_STDC_VERSION >= 201112L && !defined(__STDC_NO_THREADS__)
# define _Py_thread_local _Thread_local
# elif defined(_MSC_VER) /* AKA NT_THREADS */
# define _Py_thread_local __declspec(thread)
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10 changes: 10 additions & 0 deletions Lib/test/test_cext/__init__.py
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Expand Up @@ -133,6 +133,11 @@ def test_build_abi3t(self):
# Test with Py_TARGET_ABI3T
self.check_build('_test_cext_abi3t', abi3t=True)

# gh-154643: Test that headers don't use undefined macros in #if
@unittest.skipIf(support.MS_WINDOWS, "MSVC doesn't support -Werror=undef")
def test_build_werror_undef(self):
self.check_build('_test_cext_undef', extra_cflags='-Werror=undef')
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class TestPublicCpp(BaseTests, unittest.TestCase):
LANGUAGE = 'C++'
Expand Down Expand Up @@ -174,6 +179,11 @@ def test_build_abi3t(self):
# Test with Py_TARGET_ABI3T
self.check_build('_test_cppext_abi3t', abi3t=True)

# gh-154643: Test that headers don't use undefined macros in #if
@unittest.skipIf(support.MS_WINDOWS, "MSVC doesn't support -Werror=undef")
def test_build_werror_undef(self):
self.check_build('_testcppext_undef', extra_cflags='-Werror=undef')


class TestInternalC(BaseTests, unittest.TestCase):
LANGUAGE = 'C'
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6 changes: 6 additions & 0 deletions Lib/test/test_cext/setup.py
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Expand Up @@ -42,6 +42,9 @@

# Ask for strict(er) compliance with the standard
'-pedantic-errors',

# gh-154643: Headers should not use undefined macros in #if
'-Werror=undef',
]
if not support.Py_GIL_DISABLED:
PUBLIC_CFLAGS.append(
Expand Down Expand Up @@ -94,6 +97,9 @@

# We also use `long long`, a C++11 feature we can enable individually.
'-Wno-long-long',

# gh-154643: Headers should not use undefined macros in #if
'-Werror=undef',
]
INTERNAL_CXXFLAGS = [
# Do not complain about unused parameteres in the internal C API
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/C_API/2026-07-24-22-30-40.gh-issue-154643.z-ZutK.rst
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@@ -0,0 +1,2 @@
In ``pyport.h`` and ``pyatomic.h`` don't use ``_Py_STDC_VERSION`` when it is
not defined, fixing build errors for C or C++ code built with ``-Werror=undef``.
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