sigaltstack
===========

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

Gnulib module: ---

Portability problems fixed by Gnulib:

Portability problems not fixed by Gnulib:

  * This function is missing on some platforms: Minix 3.1.8, Cygwin 1.7.x, mingw, MSVC 14.

  * sigaltstack doesn't work on HP-UX 11/IA-64 and OpenBSD 3.6/Sparc64.

  * This function interprets the ss_sp member of stack_t as the upper bound instead of the lower bound of the alternate stack on some platforms: IRIX 6.5