sigsetjmp - set jump point for a non-local goto
The sigsetjmp() function shall be equivalent to the setjmp() function, except as follows:
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 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.
siglongjmp(), signal(), sigprocmask(), sigsuspend(), the Base Definitions volume of IEEE Std 1003.1-2001, <setjmp.h>
First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.
The DESCRIPTION is updated for alignment with the POSIX Threads Extension.
The DESCRIPTION is reworded in terms of setjmp().
The SYNOPSIS is marked CX since the presence of this function in the <setjmp.h> header is an extension over the ISO C standard.