[v1] selftests/futex: clang-inspired fixes

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

Posted by John Hubbard 1 year, 7 months ago

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.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 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 := \
-- 
2.45.0

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

Posted by John Hubbard 1 year, 7 months ago

On 5/2/24 9:18 PM, 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:

Hi Shuah, Edward and all,

This patch now seems to be obsolete, due to Edward Liaw's comprehensive
fix, "[PATCH v2 0/5] Define _GNU_SOURCE for sources using" [1].

[1] https://lore.kernel.org/20240507214254.2787305-1-edliaw@google.com

A process question for Shuah: shall I gather up the selftest patches
that have reviews and acks, and post them with the versions incremented?

I'm new to this list, and I'm not sure of your exact workflow. And there
are admittedly a flurry of patches involved.

[1] https://lore.kernel.org/20240507214254.2787305-1-edliaw@google.com

thanks,
-- 
John Hubbard
NVIDIA

> 
>      $(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.
> 
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>   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 := \

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

Posted by Edward Liaw 1 year, 6 months ago

On Wed, May 8, 2024 at 2:05 PM John Hubbard <jhubbard@nvidia.com> wrote:
>
> On 5/2/24 9:18 PM, 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:
>
> Hi Shuah, Edward and all,
>
> This patch now seems to be obsolete, due to Edward Liaw's comprehensive
> fix, "[PATCH v2 0/5] Define _GNU_SOURCE for sources using" [1].
>
> [1] https://lore.kernel.org/20240507214254.2787305-1-edliaw@google.com

Since we're dropping that patch, would we be able to merge this one?
This should resolve the futex_requeue_pi compiler warnings with Clang.

Reviewed-by: Edward Liaw <edliaw@google.com>

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

Posted by John Hubbard 1 year, 6 months ago

On 5/28/24 3:24 PM, Edward Liaw wrote:
> On Wed, May 8, 2024 at 2:05 PM John Hubbard <jhubbard@nvidia.com> wrote:
>>
>> On 5/2/24 9:18 PM, 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:
>>
>> Hi Shuah, Edward and all,
>>
>> This patch now seems to be obsolete, due to Edward Liaw's comprehensive
>> fix, "[PATCH v2 0/5] Define _GNU_SOURCE for sources using" [1].
>>
>> [1] https://lore.kernel.org/20240507214254.2787305-1-edliaw@google.com
> 
> Since we're dropping that patch, would we be able to merge this one?
> This should resolve the futex_requeue_pi compiler warnings with Clang.
> 
> Reviewed-by: Edward Liaw <edliaw@google.com>

Thanks for the review! I can post a v2 of this tiny series that has only
patches 1 and 3, rebased on -rc1, so that it's clear what to merge.


thanks,
-- 
John Hubbard
NVIDIA