NAME    [Toc]    [Back]

       sigstack - Set and get the signal stack context

SYNOPSIS    [Toc]    [Back]

       #include <signal.h>

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

STANDARDS    [Toc]    [Back]

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

       sigstack():  XSH4.0, XSH4.2, XSH5.0

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

PARAMETERS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

       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 current 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    [Toc]    [Back]

       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 defined as a LEGACY function by
       the  XSH  specification. XSH recommends that sigaltstack()
       rather than sigstack() be used when creating or  rewriting
       portable applications.

RETURN VALUES    [Toc]    [Back]

       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    [Toc]    [Back]

       The  sigstack() function sets errno to the specified value
       for the following conditions: [Tru64 UNIX]  The instack or
       outstack  parameter points outside of the address space of
       the process.  An attempt was  made  to  modify  an  active
       stack.

SEE ALSO    [Toc]    [Back]

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

       Standards: standards(5)



                                                      sigstack(2)