OSF

NAME

sigstack − Sets and gets signal stack context

SYNOPSIS

#include <signal.h> int sigstack (
struct sigstack ∗instack,
struct sigstack ∗outstack );

PARAMETERS

instackSpecifies the stack pointer of the new signal stack.  If the value of the instack parameter is nonzero, it points to a sigstack() structure, which has the following members: struct sigstack{
caddr_tss_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. 

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

DESCRIPTION

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

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 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. 

CAUTION

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

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

If the sigstack() function fails, errno may be set to the following value:

[EFAULT]The instack or outstack parameter points outside of the address space of the process. 

RELATED INFORMATION

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