From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 08 Nov 2013 19:18:27 +0100
From: Jan Kiszka <jan.kiszka@siemens.com>
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Subject: Re: [Xenomai] [Xenomai-forge] [PATCH] Silence unused_result warning
	from write()
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To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>, Gernot Hillier <gernot.hillier@siemens.com>
Cc: xenomai@xenomai.org

On 2013-11-08 18:23, Gilles Chanteperdrix wrote:
> On 11/08/2013 06:55 AM, Gernot Hillier wrote:
>> Am 07.11.2013 19:01, schrieb Gilles Chanteperdrix:
>>> On 11/07/2013 10:22 AM, Gernot Hillier wrote:
>>>> Some glibc versions mark write() with attribute warn_unused_result (found in
>>>> Ubuntu 12.04 / eglibc 2.15 / gcc 4.6.3), so we need to silence this warning,
>>>> especially when building with -Werror.
>>>
>>> Why not casting write result to void, it does not work?
>>>
>>
>> No, it doesn't. For rationale, please see 
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25509.
>>
> Ok, but I do not like your patch anyway:
> - it compares directly the function result, which no other code in
> Xenomai sources does, we always store the result in a variable and test
> the variable
> - it opens and closes braces for no good reason.
> 
> I believe you still can do:
> 
> rc = write
> (void)rc

Yep, that's what other projects do as well when there is really no use
for the return code.

> 
> The link you sent also indicates that the warning can be disabled with
> -Wno-unused-result
> 
> Can you not compile with this option on distributions with this behaviour?

Let's fix this in our source code, not in the ./configure command line.
I expect the warning to become more frequent with recent compilers
and/or distros.

Jan

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