Martin Sebor wrote:
>Travis Vitek wrote:
>> Martin Sebor wrote:
>>
>>> AFAIK, catopen() and catgets() are not required to be thread
>>> safe so we need to guard calls to them across all instances of
>>> the facet.
>>>
>>
>> Yes, but the affected functions are doing more than just calling
>> catgets() and catopen(). Since they are using shared data, they
>> need to lock that shared data with a shared mutex.
>
>And unless I'm missing something, they are.
>
> _RWSTD_MT_STATIC_GUARD (__rw_open_cat_data);
>
>This provides mutual exclusion across all othe such guards
>(i.e, those with the same type as an argument).
>
Nope. See _defs.h...
// synchronizes access by all objects holding the same mutex
# define _RWSTD_MT_GUARD(mutex) \
_RW::__rw_guard _RWSTD_PASTE (__guard, __LINE__) (mutex)
// synchronizes access by all threads holding the same mutex
# define _RWSTD_MT_STATIC_GUARD(type) \
typedef _RW::__rw_type<type,__LINE__> _UniqueType; \
_RWSTD_MT_CLASS_GUARD(_UniqueType)
// synchronizes access by all objects of the same type
# define _RWSTD_MT_CLASS_GUARD(type) \
_RWSTD_MT_GUARD (_RW::__rw_get_static_mutex ((type*)0))
_RWSTD_MT_CLASS_GUARD locks a static mutex that unique for the type
provided. This provides the behavior that you are describing above.
_RWSTD_MT_STATIC_GUARD creates a unique type given a type and a line
number. That new type is then used to get a handle to a static mutex.
The only time two _RWSTD_MT_STATIC_GUARD lines are guarding the same
mutex is if they happen to be on the same line number and have the
same type argument.
Travis
