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Date: Fri, 13 Jul 2012 18:18:09 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 1/2] coroutine-ucontext: Help valgrind
 understand coroutines
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To: Eric Blake <eblake@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org

Am 13.07.2012 18:13, schrieb Eric Blake:
> On 07/13/2012 10:06 AM, Kevin Wolf wrote:
>> Am 13.07.2012 17:37, schrieb Peter Maydell:
>>> On 13 July 2012 16:31, Kevin Wolf <kwolf@redhat.com> wrote:
>>>> +#ifdef CONFIG_VALGRIND_H
>>>> +/* Work around an unused variable in the valgrind.h macro... */
>>>> +#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
>>>> +static inline void valgrind_stack_deregister(CoroutineUContext *co)
>>>> +{
>>>> +    VALGRIND_STACK_DEREGISTER(co->valgrind_stack_id);
>>>> +}
>>>> +#pragma GCC diagnostic error "-Wunused-but-set-variable"
>>>> +#endif
>>>
>>> '#pragma .. error' will defeat the configure code which makes warnings
>>> not fatal in release builds.
>>
>> I know. What's your suggestion? Switch only to warning? Then it would be
>> easy to miss warnings. Disabling the valgrind code for gcc < 4.6 is
>> better, but still not really nice.
> 
> But you're already disabling the valgrind code for gcc too old to honor
> 
> #pragma GCC diagnostic ignored "-Wunused-but-set-variable"
> 
> so what's the difference in making your configure check for
> CONFIG_VALGRIND_H _also_ check that gcc is new enough to honor push/pop
> of diagnostic?

The practical difference for me is that the RHEL 6 gcc knows
ignored/warning/error (since gcc 4.2), but not push/pop (since gcc 4.6),
so my test machine still wouldn't have valgrind support and I could drop
the patch wholesale.

Kevin