sigstack(2)                                           sigstack(2)



     NAME
          sigstack - set and/or get signal stack context

     SYNOPSIS
          #include <signal.h>

          struct sigstack {
             caddrt     sssp;
             int    ssonstack;
          };

          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 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 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).








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