SIGSTACK(2)							System Calls Manual						       SIGSTACK(2)

NAME

       sigstack - set and/or get signal stack context

SYNOPSIS

       #include <signal.h>

       struct sigstack {
       caddr_t	 ss_sp;
       int  ss_onstack;
       };

       sigstack(ss, oss);
       struct sigstack *ss, *oss;

DESCRIPTION

       Sigstack allows users to define an alternate stack on which signals are to be processed.  If ss is non-zero, it specifies a signal stack on
       which to deliver signals and tells the system if the process is currently executing on that stack.  When a signal's  action  indicates  its
       handler	should execute on the signal stack (specified with a sigvec(2) call), the system checks to see if the process is currently execut-
       ing on that stack.  If the process is not currently executing on the signal stack, the system arranges a switch to the signal stack for the
       duration of the signal handler's execution.  If oss is non-zero, the current signal stack state is returned.

NOTES

       Signal stacks are not ``grown'' automatically, as is done for the normal stack.	If the stack overflows unpredictable results may occur.

RETURN VALUE

       Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS

       Sigstack will fail and the signal stack context will remain unchanged if one of the following occurs.

       [EFAULT]       Either ss or oss points to memory that is not a valid part of the process address space.

SEE ALSO

       sigvec(2), setjmp(3)

4.2 Berkeley Distribution					   June 30, 1985						       SIGSTACK(2)