Re: [Xen-devel] [PATCH] symbols.c: Avoid warn_unused_result build failure on fgets().

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.11.15 at 06:03, <haozhong.zhang@xxxxxxxxx> wrote:
> On 11/04/15 07:04, Jan Beulich wrote:
>> >>> On 04.11.15 at 12:39, <riku.voipio@xxxxxxxxxx> wrote:
>> > In commit:
>> > 
>> > d37d63d symbols: prefix static symbols with their source file names
>> > 
>> > An unchecked fgets was added. This causes a compile error:
>> > 
>> > symbols.c: In function 'read_symbol':
>> > symbols.c:181:3: error: ignoring return value of 'fgets', declared with
>> > attribute warn_unused_result [-Werror=unused-result]
>> >    fgets(str, 500, in); /* discard rest of line */
>> >    ^
>> > 
>> > Paper over the warning like in the other similar fgets-on-error-path
>> > earlier in the same file.
>> 
>> But the two cases are dissimilar - the original one skips a line the
>> format of which is not recognized, while here you may be converting
>> success into an error. (I did notice the comment on the earlier fgets(),
>> but since so far I didn't get any compiler warning on any system I
>> built this on, I assumed we'd be fine without the check, since if we
>> need the check, then it will end up even more clumsy than the other
>> one.)
>>
> 
> Hi Riku and Jan,
> 
> Will there be any fix for this error? I got the same error when
> compiling Xen (commit 6f04de6) by gcc 4.8.4 on Ubuntu 14.04.3. And
> adding "(void)" ahead of fgets() in the existing code cannot eliminate
> the error/warning message.

I expect / welcome an (updated) patch.

Jan


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