Re: [PATCH 1/1] tools feature gettid: Undef _GNU_SOURCE before defining it

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Sep 28, 2026 at 02:02:45PM +0200, Arnaldo Carvalho de Melo wrote:
> Since most of tools/build/feature/test-*.c feature tests are included in
> tools/build/feature/test-all.c, we can't just define _GNU_SOURCE as it
> may already been defined and this will break the build with:
> 
>   acme@alta:~$ cat /tmp/build/perf-tools-next/feature/test-all.make.output
>   In file included from test-all.c:26:
>   test-gettid.c:3:9: error: "_GNU_SOURCE" redefined [-Werror]
>       3 | #define _GNU_SOURCE
>         |         ^~~~~~~~~~~
>   In file included from /usr/include/python3.13/pyconfig.h:9,
>                    from /usr/include/python3.13/Python.h:14,
>                    from test-python-module.c:2,
>                    from test-all.c:14:
>   /usr/include/aarch64-linux-gnu/python3.13/pyconfig.h:1810:10: note: this is the location of the previous definition
>    1810 | # define _GNU_SOURCE 1
>         |          ^~~~~~~~~~~
>   cc1: all warnings being treated as errors
>   acme@alta:~$
> 
> I.e. pyconfig.h is included by the new test-python-module.c, that is at
> the start of test-all.c, defines _GNU_SOURCE, noticed on Debian 13
> (/usr/include/aarch64-linux-gnu/python3.13/pyconfig.h, libpython
> 3.13.5-2+deb13u5), and then test-all.c includes test-gettid.c that was

Noticed as well on fedora:

make: Leaving directory '/home/acme/git/perf-tools-next/tools/perf'
105: 'import perf' in python                                                                                   : Ok

=== Test Summary ===
Passed main tests : 1
Passed subtests   : 0
Skipped tests     : 0
Failed tests      : 0
In file included from test-all.c:26:
test-gettid.c:3:9: error: ‘_GNU_SOURCE’ redefined [-Werror]
    3 | #define _GNU_SOURCE
      |         ^~~~~~~~~~~
In file included from /usr/include/python3.14/pyconfig.h:6,
                 from /usr/include/python3.14/Python.h:14,
                 from test-python-module.c:2,
                 from test-all.c:14:
/usr/include/python3.14/pyconfig-64.h:1879:10: note: this is the location of the previous definition
 1879 | # define _GNU_SOURCE 1
      |          ^~~~~~~~~~~
cc1: all warnings being treated as errors
⬢ [acme@toolbx perf-tools-next]$ head /etc/os-release
NAME="Fedora Linux"
VERSION="44 (Toolbx Container Image)"
RELEASE_TYPE=stable
ID=fedora
VERSION_ID=44
VERSION_CODENAME=""
PRETTY_NAME="Fedora Linux 44 (Toolbx Container Image)"
ANSI_COLOR="0;38;2;60;110;180"
LOGO=fedora-logo-icon
CPE_NAME="cpe:/o:fedoraproject:fedora:44"
⬢ [acme@toolbx perf-tools-next]$