longjmp
=======

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

Gnulib module: ---

Portability problems fixed by Gnulib:

Portability problems not fixed by Gnulib:

  * The effects of this call are system and compiler optimization dependent, since it restores the contents of register-allocated variables but not the contents of stack-allocated variables.

  * When longjumping out of a signal handler that was being executed on an alternate stack (installed through sigaltstack), on FreeBSD, NetBSD, OpenBSD, you need to clear the SS_ONSTACK flag in the stack_t structure managed by the kernel.