Re: [PATCH] include/builddefs.in: ignore unused-result warning

[Shiyang Ruan <ruansy.fnst@fujitsu.com>]

在 2025/1/15 23:33, Zorro Lang 写道:
> On Mon, Jan 06, 2025 at 05:59:06PM +0800, Shiyang Ruan wrote:
>> When build xfstests, a lot of "unused result" warning are reported:
>>
>>      [CC] write_log.lo
>> write_log.c: In function 'wlog_record_write':
>> write_log.c:205:13: warning: ignoring return value of 'write' declared with attribute 'warn_unused_result' [-Wunused-result]
>>    205 |             write(wfile->w_afd, wbuf, reclen);
>>        |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> write_log.c:209:13: warning: ignoring return value of 'write' declared with attribute 'warn_unused_result' [-Wunused-result]
>>    209 |             write(wfile->w_rfd, wbuf, reclen);
>>        |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>      [CC] random.lo
> 
> Hi,
> 
> I never hit this build warning:
> 
> # make
> ...
> Building lib
>      [LTDEP]
>      [CC] write_log.lo
>      [LD]
> Building ltp
>      [CC]    doio
>      [CC]    fsstress
> ...
> 
> Besides that ...

Could you share me the info of your build environment?  Such as OS, 
kernel, gcc version.  I'd like to find out what wrong with mine.


--
Thanks,
Ruan.

> 
>>
>> Mostly are calused by not using the return value of read()/write()/...
>> Ignore this warning by adding `-Wno-unused-result` to CCFLAGS.  This
>> won't cause other problem but make the log clean.
>>
>> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
>> ---
>>   include/builddefs.in | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/builddefs.in b/include/builddefs.in
>> index 7274cde8d..edf87ff00 100644
>> --- a/include/builddefs.in
>> +++ b/include/builddefs.in
>> @@ -75,7 +75,7 @@ HAVE_RLIMIT_NOFILE = @have_rlimit_nofile@
>>   NEED_INTERNAL_XFS_IOC_EXCHANGE_RANGE = @need_internal_xfs_ioc_exchange_range@
>>   HAVE_FICLONE = @have_ficlone@
>>   
>> -GCCFLAGS = -funsigned-char -fno-strict-aliasing -Wall
>> +GCCFLAGS = -funsigned-char -fno-strict-aliasing -Wall -Wno-unused-result
> 
> I'm not an expert of gcc. From the manual of gcc, it says:
> 
>         -Wno-unused-result
>             Do not warn if a caller of a function marked with attribute "warn_unused_result" does not use its return value. The default is -Wunused-result.
> 
> Looks like the "-Wno-unused-result" works for "a function marked with
> attribute warn_unused_result", e.g.
> 
>      int __attribute__((warn_unused_result)) foo(void)
> 
> I think fstests doesn't use that attribute.
> 
> Thanks,
> Zorro
> 
> 
>>   
>>   ifeq ($(PKG_PLATFORM),linux)
>>   PCFLAGS = -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 $(GCCFLAGS)
>> -- 
>> 2.43.0
>>
>>
>