[alsa-devel] [PATCH alsa-lib 1/2] pcm_share: Fix compiler warnings -Wunused-result

[Takashi Iwai]

On Thu, 15 Nov 2018 08:19:56 +0100,
Kirill Marinushkin wrote:
> 
> Before this commit, compilation of `pcm_share` causes warnings "ignoring
> return value" for several `read` and `write` operations:
> 
> ~~~~
> pcm_share.c: In function '_snd_pcm_share_missing':
> pcm_share.c:293:5: warning: ignoring return value of 'read', declared with
> attribute warn_unused_result [-Wunused-result]
>      read(share->slave_socket, buf, 1);
>      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> <...>
> ~~~~
> 
> However, ignoring return values in these use-cases is safe and optimal,
> because `read` and `write` operations are executed upon descriptors,
> created with `socketpair()` and `pipe()`.
> 
> This commit fixes the warnings by introducing the return value with the
> attribute `unused` (for details, see [1]). The macro, used in this commit,
> is defined at `global.h`:
> 
> ~~~~
> define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
> ~~~~
> 
> I explicitly checked the objdump: this commit doesn't change the machine
> code, related to the modified C code lines. The execution performance is
> not affected.
> 
> [1] https://gcc.gnu.org/onlinedocs/gcc-8.2.0/gcc/Common-Variable-Attributes.html
> 
> Signed-off-by: Kirill Marinushkin <kmarinushkin at birdec.tech>

Which compiler version?  I'm using gcc 8.2.1, and couldn't get any
warnings like the above.


thanks,

Takashi