[rtems commit] semopen.c: Address set but unused variable warning

[Joel Sherrill]

You get a statement with no effect warning.

Joel Sherrill <Joel.Sherrill at oarcorp.com> wrote:


Does that work or generate an warning about statement with no effect?

Gedare Bloom <gedare at rtems.org> wrote:


On Sun, Sep 22, 2013 at 10:45 AM, Joel Sherrill
<joel.sherrill at oarcorp.com> wrote:
> There is precedence for using the compiler attributes
> so I just added that and switched.
>
I think it might be better to avoid compiler attributes when there is
a language-level alternative that is compiler-agnostic. In this case,
the use of:
(void) var;
seems fine to me.

> Thanks for the feedback.
>
> If we have a print format string to use for mode_t and
> wchar_t, a few more cases would be fixed.
>
> On 9/22/2013 7:32 AM, Pavel Pisa wrote:
>> Hello Ralf and others,
>>
>> On Sunday 22 of September 2013 05:01:49 Ralf Corsepius wrote:
>>>> diff --git a/cpukit/posix/src/semopen.c b/cpukit/posix/src/semopen.c
>>>> index b863080..e61fad0 100644
>>>> --- a/cpukit/posix/src/semopen.c
>>>> +++ b/cpukit/posix/src/semopen.c
>>>> @@ -43,6 +43,14 @@
>>>>    *        parameters must be present.
>>>>    */
>>>>
>>>> +/*
>>>> + * mode is set but never used. GCC gives a warning for this
>>>> + * and we need to tell GCC not to complain. But we have to
>>>> + * have it because we have to work through the variable
>>>> + * arguments to get to attr.
>>>> + */
>>>> +#pragma GCC diagnostic push
>>>> +#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
>>>>   sem_t *sem_open(
>>>>     const char *name,
>>>>     int         oflag,
>>>> @@ -137,3 +145,4 @@ return_id:
>>>>       return (sem_t *)&the_semaphore->Object.id;
>>>>     #endif
>>>>   }
>>>> +#pragma GCC diagnostic pop
>>>
>>> Why this brutal and probably non-portable way to suppress warnings?
>>>
>>> Why doesn't __attribute__((unused)) or similar suffice?
>>
>> I would prefer to see something like RTEMS_ATTR_UNUSED to support
>> multiple compilers. You can look at my collection of these in
>> uLUt definitions file
>>
>> http://sourceforge.net/p/ulan/ulut/ci/master/tree/ulut/ul_utdefs.h
>>
>> I declare file contents (by this e-mail) as free for public
>> domain use (uLUt as whole is is GPL/LGPL/MPL RTEMS compatible too).
>>
>> As for the actual __attribute__((unused)) there is even portable
>> solution which does not depend on GCC extension.
>>
>> {
>>   int my_unused_var;
>>   (void) my_unused_var;
>> }
>>
>> This solution should be accepted by all compilers and is suggested
>> by some people as better option.
>>
>> Best wishes,
>>
>>              Pavel
>> _______________________________________________
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>> rtems-devel at rtems.org
>> http://www.rtems.org/mailman/listinfo/rtems-devel
>>
>
>
>
> --
> Joel Sherrill, Ph.D.             Director of Research & Development
> joel.sherrill at OARcorp.com        On-Line Applications Research
> Ask me about RTEMS: a free RTOS  Huntsville AL 35805
> Support Available                (256) 722-9985
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