Re: [Qemu-devel] [PATCH] clang: Disable warning about expansion to 'defined'

[Paolo Bonzini]

On 09/08/2016 10:17, Peter Maydell wrote:
> On 9 August 2016 at 09:15, Paolo Bonzini <address@hidden> wrote:
>>
>>
>> On 09/08/2016 10:09, Peter Maydell wrote:
>>> Is this the only thing in our code which provokes the warning?
>>> If so, why don't we just fix it to not be undefined behaviour?
>>
>> Indeed that was my first suggestion yesterday.  However, we use -Wundef
>> (a good idea, I think), and fixing it would cause the -Wundef warning to
>> appear instead.
> 
> Why would
> #if !defined(SPICE_SERVER_VERSION) || (SPICE_SERVER_VERSION < 0xc06)
> #define SPICE_NEEDS_SET_MM_TIME 1
> #else
> #define SPICE_NEEDS_SET_MM_TIME 0
> #endif
> 
> provoke a Wundef warning?

Oh, that would work indeed.  I was thinking of simplifying the
definition of SPICE_NEEDS_SET_MM_TIME like this:

#define SPICE_NEEDS_SET_MM_TIME (SPICE_SERVER_VERSION < 0xc06)

If we do this, it would make sense to add -Wexpansion-to-defined to GCC
and enable it (though I still believe it's wrong to add it to -Wall).

Thanks,

Paolo