[PATCH] D21637: [libcxx] Don't use pthread initializers in constexpr constructors

[Eric Fiselier via cfe-commits]

EricWF added a comment.

In http://reviews.llvm.org/D21637#471151, @rmaprath wrote:

> Small side question: so how are `__m_` and `__cv_` initialized in this setup? is it that `pthread_mutex_lock()` and the like would be able to handle an un-initialized blob of memory (in a thread-safe way)? Because I don't see a call to `pthread_mutex_init()` anywhere in the code-path.


`__m_` and `__cv_` are initialized during  non-static data member initialization. They didn't previously call pthread_mutex_lock(), instead they directly initialized '__m_' and '__cv_' in the constructors initializer list.

And according to the current spec we are allowed to use PTHREAD_MUTEX_INITIALIZER to initialize non-static mutexes.
http://pubs.opengroup.org/onlinepubs/9699919799/

> In cases where default mutex attributes are appropriate, the macro PTHREAD_MUTEX_INITIALIZER can be used to initialize mutexes.

>  The effect shall be equivalent to dynamic initialization by a call to pthread_mutex_init() with parameter attr specified as NULL, except that no error checks are performed.





http://reviews.llvm.org/D21637