sigstack(2)                                           sigstack(2)



NAME
     sigstack - set or get signal stack context

SYNOPSIS
     #include <signal.h>

     struct sigstack {
         caddr_t    ss_sp;
         int ss_onstack;
     };

     int 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 nonzero, 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 executing
     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 nonzero, 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.

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

     The sigstack command will fail and the signal stack context
     will remain unchanged if 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), signal(3)








January 1992                                                    1