posix: implement pthread_cleanup_pop()

[ycsin]

There are currently 20 missing POSIX functions with trivial implementations, pthread_cleanup_pop() is one of them.

pthread_cleanup_pop, pthread_cleanup_push - establish cancellation handlers

The pthread_cleanup_pop() function shall remove the routine at the top of the calling thread's cancellation cleanup stack and optionally invoke it (if execute is non-zero).

The pthread_cleanup_push() function shall push the specified cancellation cleanup handler routine onto the calling thread's cancellation cleanup stack. The cancellation cleanup handler shall be popped from the cancellation cleanup stack and invoked with the argument arg when:

The thread exits (that is, calls pthread_exit()).

The thread acts upon a cancellation request.

The thread calls pthread_cleanup_pop() with a non-zero execute argument.

It is unspecified whether pthread_cleanup_push() and pthread_cleanup_pop() are macros or functions. If a macro definition is suppressed in order to access an actual function, or a program defines an external identifier with any of these names, the behavior is undefined. The application shall ensure that they appear as statements, and in pairs within the same lexical scope (that is, the pthread_cleanup_push() macro may be thought to expand to a token list whose first token is '{' with pthread_cleanup_pop() expanding to a token list whose last token is the corresponding '}' ).

The effect of calling longjmp() or siglongjmp() is undefined if there have been any calls to pthread_cleanup_push() or pthread_cleanup_pop() made without the matching call since the jump buffer was filled. The effect of calling longjmp() or siglongjmp() from inside a cancellation cleanup handler is also undefined unless the jump buffer was also filled in the cancellation cleanup handler.

The effect of the use of return, break, continue, and goto to prematurely leave a code block described by a pair of pthread_cleanup_push() and pthread_cleanup_pop() functions calls is undefined.

See https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_cleanup_pop.html

See RFC #51211 for more info.