GNU bug report logs - #11829
Build failure with --enable-gcc-warnings

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Message #16 received at 11829 <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Eric Blake <eblake <at> redhat.com>
Cc: 11829 <at> debbugs.gnu.org
Subject: Re: bug#11829: Build failure with --enable-gcc-warnings
Date: Sun, 01 Jul 2012 00:47:02 +0100

On 07/01/2012 12:38 AM, Eric Blake wrote:
> On 06/30/2012 05:10 PM, Pádraig Brady wrote:
> 
>> This should address it:
>>
>> commit 8f4dcad477da1a952a04478ae125d5453f29dcc9
>> Author: Pádraig Brady <P <at> draigBrady.com>
>> Date:   Sun Jul 1 00:04:37 2012 +0100
>>
>>     maint: avoid a -Wunsed-but-set warning on some systems
>>
>>     * src/stty.c (main): Mark speed_was_set as unused when
>>     CIBAUD undefined (like on ppc64 GNU/Linux for example).
>>     Reported-by: Stefano Lattarini
>>
>> diff --git a/src/stty.c b/src/stty.c
>> index 83b502c..b2dd849 100644
>> --- a/src/stty.c
>> +++ b/src/stty.c
>> @@ -737,7 +737,11 @@ main (int argc, char **argv)
>>    int argi = 0;
>>    int opti = 1;
>>    bool require_set_attr;
>> +#ifdef CIBAUD
>>    bool speed_was_set;
>> +#else
>> +  bool speed_was_set ATTRIBUTE_UNUSED;
>> +#endif
> 
> Three lines too many.  ATTRIBUTE_UNUSED is defined by gcc to mean 'might
> be unused, therefore don't warn if it was not used', and not 'must not
> be used, and therefore warn if it is used'.  Therefore, it is always
> safe to use the one-liner:
> 
> bool speed_was_set ATTRIBUTE_UNUSED;
> 
> even if, when CIBAUD is defined, it was actually used.  No need for
> extra #ifdef.
> 

But then you would never get such warnings for this variable.
I was trying to disable the warning only where it's incorrect,
and thought the single ifdef worth it?

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