[HarfBuzz] [PATCH] Implement threading primitives on Windows; fix compile error and leak

[Bradley Grainger]

>> Now, since we are using C++ in HarfBuzz, I wonder if we can use 
>> constructors to initialize the static mutexes automatically?
>
> This little gem seems to do the trick:
>
> struct hb_static_mutex_t : hb_mutex_t
> {
>   hb_static_mutex_t (void) {
>     hb_mutex_init (this);
>   }
> };
>
>
> What do you think?

I _think_ this is OK, because critical sections are allowed be initialised in DllMain (according to http://msdn.microsoft.com/en-us/library/ms682583.aspx): "There are serious limits on what you can do in a DLL entry point. ... If your DLL is linked with the C run-time library (CRT), the entry point provided by the CRT calls the constructors and destructors for global and static C++ objects. Therefore, these restrictions for DllMain also apply to constructors and destructors and any code that is called from them" but "For example, DllMain can create synchronization objects such as critical sections and mutexes"

It does seem like this would need a destructor, too, to avoid leaking CRITICAL_SECTION objects (unless they're only ever destroyed at process shutdown, when it wouldn't be necessary). Of course, then the struct would need to be made non-copyable to avoid inadvertent early destruction.

Bradley