int sigsetjmp(sigjmp_buf env, int savemask);
The sigsetjmp() function shall be equivalent to the setjmp() function, except as follows:
- References to setjmp() are equivalent to sigsetjmp().
- References to longjmp() are equivalent to siglongjmp().
- If the value of the savemask argument is not 0, sigsetjmp() shall also save the current signal mask of the calling thread as part of the calling environment.
If the return is from a successful direct invocation, sigsetjmp() shall return 0. If the return is from a call to siglongjmp(), sigsetjmp() shall return a non-zero value.
No errors are defined.
The following sections are informative.
The distinction between setjmp()/ longjmp() and sigsetjmp()/ siglongjmp() is only significant for programs which use sigaction(), sigprocmask(), or sigsuspend().
Note that since this function is defined in terms of setjmp(), if savemask is zero, it is unspecified whether the signal mask is saved.
The ISO C standard specifies various restrictions on the usage of the setjmp() macro in order to permit implementors to recognize the name in the compiler and not implement an actual function. These same restrictions apply to the sigsetjmp() macro.
There are processors that cannot easily support these calls, but this was not considered a sufficient reason to exclude them.
4.2 BSD, 4.3 BSD, and XSI-conformant systems provide functions named _setjmp() and _longjmp() that, together with setjmp() and longjmp(), provide the same functionality as sigsetjmp() and siglongjmp(). On those systems, setjmp() and longjmp() save and restore signal masks, while _setjmp() and _longjmp() do not. On System V Release 3 and in corresponding issues of the SVID, setjmp() and longjmp() are explicitly defined not to save and restore signal masks. In order to permit existing practice in both cases, the relation of setjmp() and longjmp() to signal masks is not specified, and a new set of functions is defined instead.
The longjmp() and siglongjmp() functions operate as in the previous issue provided the matching setjmp() or sigsetjmp() has been performed in the same thread. Non-local jumps into contexts saved by other threads would be at best a questionable practice and were not considered worthy of standardization.
COPYRIGHTPortions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .