[Mesa-dev] [PATCH 1/2] util: Add assume() macro.

[Matt Turner]

On Thu, Oct 2, 2014 at 1:58 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> On Tuesday, September 30, 2014 04:24:39 PM Matt Turner wrote:
>> ---
>>  src/util/macros.h | 13 +++++++++++++
>>  1 file changed, 13 insertions(+)
>>
>> diff --git a/src/util/macros.h b/src/util/macros.h
>> index 40ebf02..77055e8 100644
>> --- a/src/util/macros.h
>> +++ b/src/util/macros.h
>> @@ -75,6 +75,19 @@ do {                        \
>>  #define unreachable(str)
>>  #endif
>>
>> +/**
>> + * Assume macro. Useful for expressing our assumptions to the compiler,
>> + * typically for purposes of silencing warnings.
>> + */
>> +#ifdef HAVE___BUILTIN_UNREACHABLE
>> +#define assume(expr) ((expr) ? (void)0 : assert(!"assumption failed"), \
>> +                                         __builtin_unreachable())
>> +#elif _MSC_VER >= 1200
>> +#define assume(expr) __assume(expr)
>> +#else
>> +#define assume(expr) assert(expr)
>> +#endif
>> +
>>  #ifdef HAVE_FUNC_ATTRIBUTE_FLATTEN
>>  #define FLATTEN __attribute__((__flatten__))
>>  #else
>>
>
> This doesn't work.  I think the precedence rules are biting you here.
>
> +#define assume(expr) ((expr) ? ((void) 0) \
> +                             : (assert(!"assumption failed"), \
> +                                __builtin_unreachable()))
>
> fixes your second patch.

Heh, ugh. :(

Will fix.