sigsetjmp(3C)                                                 sigsetjmp(3C)

NAME
     sigsetjmp, siglongjmp - a non-local goto with signal state

SYNOPSIS
     #include <setjmp.h>

     int sigsetjmp(sigjmpbuf env, int savemask);

     void siglongjmp(sigjmpbuf env, int val);

DESCRIPTION
     Using these functions, errors and interrupts encountered in a low-
     level subroutine of a program can be handled.

     sigsetjmp() saves the calling process' registers and stack environment
     [see sigaltstack(2)] in env (whose type, sigjmpbuf, is defined in the
     setjmp.h header file) for later use by siglongjmp(). If savemask is
     non-zero, the calling process' signal mask [see sigprocmask(2)] and
     scheduling parameters [see priocntl(2)] are also saved. sigsetjmp()
     returns the value 0.

     siglongjmp() restores the environment saved by the last call of
     sigsetjmp() with the corresponding env argument. After siglongjmp() is
     completed, program execution continues as if the corresponding call of
     sigsetjmp() had just returned the value val. siglongjmp() cannot cause
     sigsetjmp() to return the value zero. If siglongjmp() is invoked with
     a second argument of zero, sigsetjmp() will return 1. At the time of
     the second return from sigsetjmp(), all external and static variables
     have values as of the time siglongjmp() is called. The values of
     register and auto variables are undefined. Register or auto variables
     whose value must be relied upon must be declared as volatile.

     All accessible objects have values as of the time siglongjmp() was
     called, except that the values of objects of automatic storage dura-
     tion which are local to the function containing the invocation of the
     corresponding sigsetjmp() which do not have volatile-qualified type
     and which are changed between the sigsetjmp() invocation and
     siglongjmp() call are indeterminate.

     An invocation of sigsetjmp() must appear in one of the following con-
     texts only:

     -  the entire controlling expression of a selection or iteration
        statement

     -  one operand of a relational or equality operator with the other
        operand an integral constant expression, with the resulting expres-
        sion being the entire controlling expression of a selection or
        iteration statement






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sigsetjmp(3C)                                                 sigsetjmp(3C)

     -  the operand of a unary operator with the resulting expression being
        the entire controlling expression of a selection or iteration
        statement

     -  the entire expression of an expression statement (possibly cast to
        void)

     If a signal-catching function interrupts sleep() and calls
     siglongjmp() to restore an environment saved prior to the sleep()
     call, the action associated with SIGALRM and time it is scheduled to
     be generated are unspecified. It is also unspecified whether the
     SIGALRM signal is blocked, unless the process' signal mask is restored
     as part of the environment.

     The function siglongjmp() restores the saved signal mask if and only
     if the env argument was initialized by a call to the sigsetjmp() func-
     tion with a non-zero savemask argument.

NOTES
     If siglongjmp() is called even though env was never primed by a call
     to sigsetjmp(), or when the last such call was in a function that has
     since returned, absolute chaos is guaranteed.

SEE ALSO
     getcontext(2), priocntl(2), sigaction(2), sigaltstack(2),
     sigprocmask(2), setjmp(3C).




























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