gh-149707: Fix compiler warning in _ctypes_test on strchr() by vstinner · Pull Request #149791 · python/cpython

vstinner · 2026-05-13T17:24:10Z

Change my_strchr() return type to "const char*" (add "const").

Fix the compiler warning:

Modules/_ctypes/_ctypes_test.c: In function 'my_strchr': Modules/_ctypes/_ctypes_test.c:451:12: warning: return discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
  451 |     return strchr(s, c);
      |            ^~~~~~

When using C23, strchr(text, ch) return type is "const char*" if text type is "const char*".

Issue: -Wdiscarded-qualifiers warning in _ctypes_test.c my_strchr() under FORTIFY_SOURCE=3 #149707

Change my_strchr() return type to "const char*" (add "const"). Fix the compiler warning: Modules/_ctypes/_ctypes_test.c: In function 'my_strchr': Modules/_ctypes/_ctypes_test.c:451:12: warning: return discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] 451 | return strchr(s, c); | ^~~~~~ When using C23, strchr(text, ch) return type is "const char*" if text type is "const char*".

vstinner · 2026-05-13T17:25:44Z

See for example the glibc commit which introduced C23 support in string/string.h.

The code is now:

extern char *strchr (const char *__s, int __c)
     __THROW __attribute_pure__ __nonnull ((1));
# if __GLIBC_USE (ISOC23) && defined __glibc_const_generic && !defined _LIBC
#  define strchr(S, C)                                         \
  __glibc_const_generic (S, const char *, strchr (S, C))
# endif

StanFromIreland · 2026-05-13T19:45:33Z

I edited the title to add the issue, someone reported this recently: #149707

StanFromIreland · 2026-05-14T07:08:18Z

 }

-EXPORT(char *)my_strchr(const char *s, int c)
+EXPORT(const char *) my_strchr(const char *s, int c)


Suggested change

EXPORT(const char *) my_strchr(const char *s, int c)

EXPORT(const char *)my_strchr(const char *s, int c)

For consistency with the others.

The majority of exported functions have a space or write EXPORT() on a separated line. I would prefer to fix all functions to add a space, but I don't think that it's worth it :-)

Ah right, I had a small sample size, I only checked a few.

miss-islington-app · 2026-05-15T11:04:55Z

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

bedevere-app · 2026-05-15T11:05:11Z

GH-149862 is a backport of this pull request to the 3.15 branch.

bedevere-app · 2026-05-15T11:05:17Z

GH-149863 is a backport of this pull request to the 3.14 branch.

bedevere-app · 2026-05-15T11:05:24Z

GH-149864 is a backport of this pull request to the 3.13 branch.

miss-islington-app · 2026-05-15T11:06:29Z

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖

…thonGH-149791) Change my_strchr() return type to "const char*" (add "const"). Fix the compiler warning: Modules/_ctypes/_ctypes_test.c: In function 'my_strchr': Modules/_ctypes/_ctypes_test.c:451:12: warning: return discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] 451 | return strchr(s, c); | ^~~~~~ When using C23, strchr(text, ch) return type is "const char*" if text type is "const char*". (cherry picked from commit 5465b69) Co-authored-by: Victor Stinner <vstinner@python.org>

miss-islington-app · 2026-05-15T11:07:04Z

Sorry @vstinner, I had trouble completing the backport.
Please retry by removing and re-adding the "needs backport to 3.15" label.
Please backport backport using cherry_picker on the command line.

cherry_picker 5465b69255890650df99debb8256e0a7bc68138b 3.15

miss-islington-app · 2026-05-15T11:07:51Z

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

…thonGH-149791) Change my_strchr() return type to "const char*" (add "const"). Fix the compiler warning: Modules/_ctypes/_ctypes_test.c: In function 'my_strchr': Modules/_ctypes/_ctypes_test.c:451:12: warning: return discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] 451 | return strchr(s, c); | ^~~~~~ When using C23, strchr(text, ch) return type is "const char*" if text type is "const char*". (cherry picked from commit 5465b69) Co-authored-by: Victor Stinner <vstinner@python.org>

miss-islington-app · 2026-05-15T11:08:24Z

Sorry @vstinner, I had trouble completing the backport.
Please retry by removing and re-adding the "needs backport to 3.15" label.
Please backport backport using cherry_picker on the command line.

cherry_picker 5465b69255890650df99debb8256e0a7bc68138b 3.15

bedevere-app · 2026-05-15T11:09:29Z

GH-149865 is a backport of this pull request to the 3.15 branch.

bedevere-app · 2026-05-15T11:09:41Z

GH-149866 is a backport of this pull request to the 3.14 branch.

bedevere-app · 2026-05-15T11:10:05Z

GH-149867 is a backport of this pull request to the 3.13 branch.

vstinner · 2026-05-15T11:18:38Z

Hum. I don't understand why the bot failed to backport the change to 3.15. I backported the change manually. I backported it to 3.15, 3.14 and 3.13 branches, I didn't notice that the bot already created backports to 3.13 and 3.14 in the meanwhile...

…149791) (#149867) gh-149707: Fix compiler warning in _ctypes_test on strchr() (#149791) Change my_strchr() return type to "const char*" (add "const"). Fix the compiler warning: Modules/_ctypes/_ctypes_test.c: In function 'my_strchr': Modules/_ctypes/_ctypes_test.c:451:12: warning: return discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] 451 | return strchr(s, c); | ^~~~~~ When using C23, strchr(text, ch) return type is "const char*" if text type is "const char*". (cherry picked from commit 5465b69)

…149791) (#149866) gh-149707: Fix compiler warning in _ctypes_test on strchr() (#149791) Change my_strchr() return type to "const char*" (add "const"). Fix the compiler warning: Modules/_ctypes/_ctypes_test.c: In function 'my_strchr': Modules/_ctypes/_ctypes_test.c:451:12: warning: return discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] 451 | return strchr(s, c); | ^~~~~~ When using C23, strchr(text, ch) return type is "const char*" if text type is "const char*". (cherry picked from commit 5465b69)

…149791) (#149865) gh-149707: Fix compiler warning in _ctypes_test on strchr() (#149791) Change my_strchr() return type to "const char*" (add "const"). Fix the compiler warning: Modules/_ctypes/_ctypes_test.c: In function 'my_strchr': Modules/_ctypes/_ctypes_test.c:451:12: warning: return discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers] 451 | return strchr(s, c); | ^~~~~~ When using C23, strchr(text, ch) return type is "const char*" if text type is "const char*". (cherry picked from commit 5465b69)

StanFromIreland · 2026-05-15T14:44:29Z

The bot is playing trick on you ;-)

vstinner added skip issue skip news labels May 13, 2026

bedevere-app Bot added the awaiting core review label May 13, 2026

vstinner added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes needs backport to 3.15 pre-release feature fixes, bugs and security fixes labels May 13, 2026

StanFromIreland changed the title ~~Fix compiler warning in _ctypes_test on strchr()~~ gh-149707: Fix compiler warning in _ctypes_test on strchr() May 13, 2026

StanFromIreland removed the skip issue label May 13, 2026

bedevere-app Bot mentioned this pull request May 13, 2026

-Wdiscarded-qualifiers warning in _ctypes_test.c my_strchr() under FORTIFY_SOURCE=3 #149707

Closed

StanFromIreland approved these changes May 14, 2026

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bedevere-app Bot added awaiting merge and removed awaiting core review labels May 14, 2026

vstinner merged commit 5465b69 into python:main May 15, 2026
70 checks passed

vstinner deleted the ctypes_test branch May 15, 2026 11:04

bedevere-app Bot removed the awaiting merge label May 15, 2026

bedevere-app Bot removed the needs backport to 3.15 pre-release feature fixes, bugs and security fixes label May 15, 2026

bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label May 15, 2026

bedevere-app Bot removed the needs backport to 3.13 bugs and security fixes label May 15, 2026

vstinner added the needs backport to 3.15 pre-release feature fixes, bugs and security fixes label May 15, 2026

miss-islington-app Bot assigned vstinner May 15, 2026

vstinner added needs backport to 3.15 pre-release feature fixes, bugs and security fixes and removed needs backport to 3.15 pre-release feature fixes, bugs and security fixes labels May 15, 2026

bedevere-app Bot removed the needs backport to 3.15 pre-release feature fixes, bugs and security fixes label May 15, 2026

	EXPORT(const char ) my_strchr(const char s, int c)
	EXPORT(const char )my_strchr(const char s, int c)

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