[PATCH] D20328: [libcxx] Externally threaded libc++ variant

[Asiri Rathnayake via cfe-commits]

rmaprath added a comment.

In http://reviews.llvm.org/D20328#456241, @mclow.lists wrote:

> > Apologies, not at program launch time but link time.
>
>
> I'm OK with that; I think that's unnecessary complication, but not a deal-breaker.
>  The choosing at program launch seems unworkable to me.
>
> [ I think that the threading implementation should be chosen by the provider of libc++, frankly. ]


The problem with the latter is the number of different platforms we have to support, each with different threading primitives. For most RTOS platforms, pthreads is a big ask and even if they can provide a subset of `<pthread>`, different platforms will have different definitions of `PTHREAD_MUTEX_INITIALIZER` for example, making it very difficult for us to build `libc++` in a platform agnostic way.


http://reviews.llvm.org/D20328