[PATCH] Add c++2a binary_semaphore

[Jonathan Wakely]

On 25/02/20 09:52 +0100, Sebastian Huber wrote:
>Hello Thomas,
>
>some operating systems provide already an implementation of binary 
>semaphores with a compatible API, e.g. RTEMS. It would be nice if I 
>could use it in libstdc++. I guess you don't want to have #ifdef 
>__rtems__ stuff in this code. What about defining a binary semaphore 
>API for gthr.h and then implement the optional futex support in 
>libgcc/gthr-posix.h?

gthr.h is supposed to be an abstraction of pthreads, not futexes. I
also don't see why more libstdc++ code should live in libgcc than
necessary.

It would be OK to add semaphore support to gthr-*.h and then have
libstdc++ either use futexes (where available) or the gthr code.