Create bindings for native mutexes

[brson]

The LittleLock type currently works by allocating a C++ lock_and_signal type. This makes it unsuitable for creating static mutexes. Create new bindings to the native mutex types, along with static initializers, port LittleLock, then delete lock_and_signal.

[emberian]

@brson would this use pthreads or the uv_mutex stuff?

[alexcrichton]

Blocked by #9243, locks have the Drop trait implemented.

[brson]

@cmr pthreads

@alexcrichton I don't know that this needs to be blocked on that. Certainly LittleLock itself couldn't be initialized statically, but we could have a yet-more-primitive mutex that could still be initialized statically. Also, from a casual glance, LittleLock's destructor is just for deallocating the lock, which would not be necessary if we had the types defined in Rust.

[brson]

Here are some comments I left in IRC

15:48 <brson> All of the mutexes in Rust are based on a C++ type defined in src/rt/sync/lock_and_signal.h
15:48 <brson> The Rust bindings for this is called LittleLock, in std::unstable::sync
15:49 <brson> the problem is that LittleLock must call into C++ to allocate the lock_and_signal type
15:50 <brson> but many mutexs need to be globally-allocated as `statics`, initialized statically to the unlocked state
15:50 <brson> so none of our locks can be declared `static`
15:51 <brson> this bug is about creating completely new mutex bindings for Rust
15:51 <brson> it will involve creating a correct declaration of the unix pthread_mutex_t as well as the equivalent type on windows
15:52 <brson> meaning, define `struct pthread_muxet_t` so that it has the same definition as in C
15:52 <brson> then creating bindings to all the appropriate pthreads functions that operate on mutexes
15:52 <brson> pthread_mutex_t may have a platform-specific definitions, so you'll need to look up how it is defined in the header files for OS X, FreeBSD, and Linux
15:53 <brson> then, once you have bindings for the unix mutex type and the Windows mutex type, create some abstraction called e.g. `NativeMutex` that delegates to them
15:54 <brson> then start replacing uses of LittleLock with NativeMutex