Re: [PATCH v2 3/3] selftests/futex: pass _GNU_SOURCE without a value to the compiler

[Shuah Khan]

On 5/28/24 20:29, John Hubbard wrote:
> It's slightly better to set _GNU_SOURCE in the source code, but if one
> must do it via the compiler invocation, then the best way to do so is
> this:
>
>      $(CC) -D_GNU_SOURCE=
>
> ...because otherwise, if this form is used:
>
>      $(CC) -D_GNU_SOURCE
>
> ...then that leads the compiler to set a value, as if you had passed in:
>
>      $(CC) -D_GNU_SOURCE=1
>
> That, in turn, leads to warnings under both gcc and clang, like this:
>
>      futex_requeue_pi.c:20: warning: "_GNU_SOURCE" redefined
>
> Fix this by using the "-D_GNU_SOURCE=" form.
>
> Reviewed-by: Edward Liaw <edliaw@xxxxxxxxxx>
> Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
>   tools/testing/selftests/futex/functional/Makefile | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile
> index a392d0917b4e..994fa3468f17 100644
> --- a/tools/testing/selftests/futex/functional/Makefile
> +++ b/tools/testing/selftests/futex/functional/Makefile
> @@ -1,6 +1,6 @@
>   # SPDX-License-Identifier: GPL-2.0
>   INCLUDES := -I../include -I../../ $(KHDR_INCLUDES)
> -CFLAGS := $(CFLAGS) -g -O2 -Wall -D_GNU_SOURCE -pthread $(INCLUDES) $(KHDR_INCLUDES)
> +CFLAGS := $(CFLAGS) -g -O2 -Wall -D_GNU_SOURCE= -pthread $(INCLUDES) $(KHDR_INCLUDES)
>   LDLIBS := -lpthread -lrt
>   
>   LOCAL_HDRS := \

This looks fine. Applied now to linux-kselftest fixes branch

thanks,
-- Shuah