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(libc.info)Non-Local Exits and Signals

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Non-Local Exits and Signals
===========================

   In BSD Unix systems, `setjmp' and `longjmp' also save and restore
the set of blocked signals; see Note: Blocking Signals.  However, the
POSIX.1 standard requires `setjmp' and `longjmp' not to change the set
of blocked signals, and provides an additional pair of functions
(`sigsetjmp' and `siglongjmp') to get the BSD behavior.

   The behavior of `setjmp' and `longjmp' in the GNU library is
controlled by feature test macros; see Note: Feature Test Macros.  The
default in the GNU system is the POSIX.1 behavior rather than the BSD
behavior.

   The facilities in this section are declared in the header file
`setjmp.h'.

 - Data Type: sigjmp_buf
     This is similar to `jmp_buf', except that it can also store state
     information about the set of blocked signals.

 - Function: int sigsetjmp (sigjmp_buf STATE, int SAVESIGS)
     This is similar to `setjmp'.  If SAVESIGS is nonzero, the set of
     blocked signals is saved in STATE and will be restored if a
     `siglongjmp' is later performed with this STATE.

 - Function: void siglongjmp (sigjmp_buf STATE, int VALUE)
     This is similar to `longjmp' except for the type of its STATE
     argument.  If the `sigsetjmp' call that set this STATE used a
     nonzero SAVESIGS flag, `siglongjmp' also restores the set of
     blocked signals.