SIGSTACK(2)                                                        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
       _S_i_g_s_t_a_c_k allows users to define an alternate stack on which signals are
       to be processed.  If _s_s is non-zero, it specifies  a  _s_i_g_n_a_l  _s_t_a_c_k  on
       which  to  deliver  signals and tells the system if the process is cur‐
       rently executing on that stack.  When a signal’s action  indicates  its
       handler  should execute on the signal stack (specified with a _s_i_g_v_e_c(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  dura‐
       tion  of  the signal handler’s execution.  If _o_s_s is non-zero, the cur‐
       rent signal stack state is returned.

NOTES
       Signal stacks are not ‘‘grown’’ automatically, as is done for the  nor‐
       mal 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 _e_r_r_n_o is set to indicate the error.

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

       [EFAULT]       Either  _s_s  or  _o_s_s 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)