pthread_sigmask
===============

POSIX specification:
 https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_sigmask.html

Gnulib module: pthread_sigmask

Portability problems fixed by Gnulib:

  * This function is missing on some platforms: Minix 3.1.8, mingw, MSVC 14.

  * This function is declared in <pthread.h> instead of <signal.h> on some platforms: FreeBSD 6.4, OpenBSD 3.8.

  * This function does nothing and always returns 0 in programs that are not linked with -lpthread on some platforms: FreeBSD 13.0, MidnightBSD 1.1, HP-UX 11.31, Solaris 9.

  * When it fails, this functions returns -1 instead of the error number on some platforms: Cygwin 1.7.5.

  * This function does not immediately raise signals that were pending before the call and unblocked by the call on some platforms: IRIX 6.5.

Portability problems not fixed by Gnulib:

  * On platforms that do not natively support this function, it has unspecified behavior in a multi-threaded process.

  * This function may not fail when the first argument is invalid on some platforms: NetBSD 8.0.