[Mesa-dev] [PATCH] util: no-op __builtin_types_compatible_p() for non-GCC compilers

[Ian Romanick]

On 3/29/19 1:54 PM, Brian Paul wrote:
> On 03/29/2019 12:58 PM, Ian Romanick wrote:
>> On 3/29/19 9:57 AM, Brian Paul wrote:
>>> __builtin_types_compatible_p() is GCC-specific and breaks the
>>> MSVC build.
>>>
>>> This intrinsic has been in u_vector_foreach() for a long time, but
>>> that macro has only recently been used in code
>>> (nir/nir_opt_comparison_pre.c) that's built with MSVC.
>>>
>>> Fixes: 2cf59861a ("nir: Add partial redundancy elimination for
>>> compares")
>>> ---
>>>   src/util/u_vector.h | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/src/util/u_vector.h b/src/util/u_vector.h
>>> index cd8a95d..6807748 100644
>>> --- a/src/util/u_vector.h
>>> +++ b/src/util/u_vector.h
>>> @@ -80,6 +80,10 @@ u_vector_finish(struct u_vector *queue)
>>>      free(queue->data);
>>>   }
>>>   +#ifndef __GNUC__
>>> +#define __builtin_types_compatible_p(x) 1
>>> +#endif
>>> +
>>>   #define u_vector_foreach(elem,
>>> queue)                                  \
>>>      STATIC_ASSERT(__builtin_types_compatible_p(__typeof__(queue),
>>> struct u_vector *)); \
>>
>> The way this is GCC builtin is used here, this should be fine.  However,
>> in case it's begin used elsewhere, we should #undef it afterwards.
> 
> That doesn't seem to work.  When u_vector_foreach() is instantiated
> later, __builtin_types_compatible_p is undefined and we error out.

Ah, right.  u_vector_foreach is itself a macro, so the
__builtin_type_compatible_p macro isn't evaluated until u_vector_foreach
is evaluated.  By that point __builtin_type_compatible_p would be undefined.

This should be fine as-is, then.  Hopefully this won't result in a
weird, hard to debug compile failure later on.

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

> -Brian
> 
> 
>   I'd
>> hate to mask some other kind of bug that may be introduced later.
>>
>>>      for (uint32_t __u_vector_offset =
>>> (queue)->tail;                                \
>>>