[Mesa-dev] [PATCH 1/2] util: Make unreachable at least be an assert

[Ian Romanick]

On 12/05/2014 01:50 PM, Matt Turner wrote:
> On Fri, Dec 5, 2014 at 1:48 PM, Ian Romanick <idr at freedesktop.org> wrote:
>> On 12/05/2014 01:42 PM, Matt Turner wrote:
>>> On Fri, Dec 5, 2014 at 1:25 PM, Ian Romanick <idr at freedesktop.org> wrote:
>>>> On 12/05/2014 01:17 PM, Carl Worth wrote:
>>>>> Previously, if __builtin_unreachable() was unavailable, the
>>>>> unreachable macro was defined to do nothing. We do better here, by at
>>>>> least still making it an assert.
>>>>> ---
>>>>>  src/util/macros.h | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/src/util/macros.h b/src/util/macros.h
>>>>> index 5fc6729..eec8b93 100644
>>>>> --- a/src/util/macros.h
>>>>> +++ b/src/util/macros.h
>>>>> @@ -82,7 +82,7 @@ do {                        \
>>>>>  #endif
>>>>>
>>>>>  #ifndef unreachable
>>>>> -#define unreachable(str)
>>>>> +#define unreachable(str) assert(!str)
>>>>
>>>> I'd make this ASSERT.  In Mesa, ASSERT only exists if DEBUG is defined.
>>>>  It seems that many distros build without -DDEBUG and without -DNDEBUG.
>>>>  I'd rather have no code for these cases in all release builds.
>>>
>>> I'm surprised by that.
>>>
>>> I see that we add -DDEBUG with --enable-debug, but from experience
>>> assert() does nothing in my regular release build (without
>>> --enable-debug). Where is NDEBUG coming from in that case? I don't see
>>> it in the macros gcc automatically defines (gcc -g -dM -E - <
>>> /dev/null).
>>
>> Right... and you need NDEBUG to no-op assert.  It has to be added by
>> hand, and it seems that the distros don't.
> 
> But I don't get assert()s in release builds, and I'm not adding NDEBUG anywhere.

That's weird... I just (today) had a case where an assert() was in a
release build, but the same ASSERT() was not.  Maybe something weird is
just happening on my end... let me double check my stuff.