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

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

在 2025/1/17 12:01, Zorro Lang 写道:
> On Thu, Jan 16, 2025 at 05:55:49PM +0800, Shiyang Ruan wrote:
>>
>>
>> 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.
> 
> Do you use gcc-15?

I'm using gcc v13, installed from Ubuntu 24.04's apt.

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-linux-gnu/13/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1 
 
  Target: x86_64-linux-gnu
Configured with: ...
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 13.3.0 (Ubuntu 13.3.0-6ubuntu2~24.04)


--
Thanks,
Ruan.

> 
>>
>>
>> --
>> 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
>>>>
>>>>
>>>
>>
>