sigstack(2)							System Calls Manual						       sigstack(2)

NAME

       sigstack - Sets and gets signal stack context

SYNOPSIS

       #include <signal.h>

       int sigstack (
	       struct sigstack *instack,
	       struct sigstack *outstack );

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       sigstack():  XPG4-UNIX

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Points to the structure describing the new signal stack.  Points to the structure where the current signal stack state is stored.

DESCRIPTION

       The sigstack() function defines an alternate stack on which signals are to be processed.

       If  the	value  of the instack parameter is nonzero, it points to a sigstack() structure, which has the following members: struct sigstack{
	    caddr_t   ss_sp;	  int ss_onstack; }

       The value of instack->ss_sp specifies the stack pointer of the new signal stack.  The value of instack->ss_onstack should be set  to  1	if
       the process is currently running on that stack; otherwise, it should be 0 (zero).

       If the value of the instack parameter is 0 (that is, a null pointer), the signal stack state is not set.

       If  the	value of the outstack parameter is nonzero, it points to a sigstack() structure into which the sigstack() function stores the cur-
       rent signal stack state.  If the value of the outstack parameter is 0 (zero), the previous signal stack state is not reported.

       When a signal occurs and its handler is to run on the signal stack, the system checks to see if the process  is	already  running  on  that
       stack.	If  so,  the process continues to run on that stack even after the handler returns.  If not, the signal handler runs on the signal
       stack, and the original stack is restored when the handler returns.

       Use the sigaction() function to specify whether a given signal handler routine is to run on the signal stack.

NOTES

       A signal stack does not automatically increase in size as a normal stack does. If the stack overflows, unpredictable results can occur.

       The sigstack() function is scheduled to be withdrawn from a future version of the X/Open CAE Specification.  When writing or rewriting por-
       table applications, use the sigaltstack() function instead of sigstack().

RETURN VALUES

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

ERRORS

       The  sigstack()	function sets errno to the specified values for the following conditions: The instack or outstack parameter points outside
       of the address space of the process.

RELATED INFORMATION

       Functions: setjmp(3), sigaction(2), sigvec(2)

       Standards: standards(5) delim off

																       sigstack(2)