[Mesa-dev] [PATCH 1/2] c11/threads: add missing brackets around _MTX_INITIALIZER_NP

[Emil Velikov]

On 02/08/14 00:26, Ian Romanick wrote:
> On 08/01/2014 09:41 AM, Emil Velikov wrote:
>> ... for win32 builds. Spotted this warning when I've imported the
>> library into waffle, and gave mingw-w64-gcc a bash at compiling it.
>>
>> src/waffle/core/wcore_display.c:37:5: warning: missing braces around
>> initializer [-Wmissing-braces]
>> static mtx_t mutex = _MTX_INITIALIZER_NP;
>> ^
>>
>> Signed-off-by: Emil Velikov <emil.l.velikov at gmail.com>
>> ---
>>  include/c11/threads_win32.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/c11/threads_win32.h b/include/c11/threads_win32.h
>> index 5298a84..35880ba 100644
>> --- a/include/c11/threads_win32.h
>> +++ b/include/c11/threads_win32.h
>> @@ -85,7 +85,7 @@ Configuration macro:
>>  #define TSS_DTOR_ITERATIONS 1
>>  
>>  // FIXME: temporary non-standard hack to ease transition
>> -#define _MTX_INITIALIZER_NP {(PCRITICAL_SECTION_DEBUG)-1, -1, 0, 0, 0, 0}
>> +#define _MTX_INITIALIZER_NP {{(PCRITICAL_SECTION_DEBUG)-1, -1, 0, 0, 0, 0}}
> 
> This is because CRITICAL_SECTION is actually a typedef of a pointer to
> some structure type, so it needs to be initialized like an array of
> strcutres.  Yeah?
> 
I wish I could agree.

CRITICAL_SECTION is a typedef of a typedef'ed struct (no pointers yet) where
the first member is a struct *, as seen below.

typedef B CRITICAL_SECTION;
typedef struct A {
   struct *bla;
   ...
} B;

I remember spending a few hours reading and experimenting with this and every
way I looked at it current code seems sane. In the end I've smashed the
brackets not to pollute the build log and carried on with other stuff :) Don't
think I have checked if MSVC complained about the issue though. Will give it a
try next time I reboot.


> I searched a bit on the net, and I could not find a single example of
> initializing a win32 CRITICAL_SECTION this way.  Is this a good idea?
> The FIXME comment doesn't inspire confidence...
> 
Same here. AFAICS one should init the "mutex" via InitializeCriticalSection or
InitializeCriticalSectionAndSpinCount. Either of which is very Win32 specific
and not at all portable. Perhaps Jose (the author) can share some more
insights on the topic ?


-Emil

>>  /*---------------------------- types ----------------------------*/
>>  typedef struct cnd_t {
>>
>