sigstack(2)                DG/UX 4.30                 sigstack(2)



     NAME
          sigstack - Set and/or get signal stack context.

     SYNOPSIS
          #include <signal.h>

          int     sigstack (new_signal_stack, old_signal_stack)
          struct sigstack        * new_signal_stack;
          struct sigstack        * old_signal_stack;

     PARAMETERS
          new_signal_stack
                         NULL or address of new signal stack context
                         specifier.


          old_signal_stack
                         NULL or address of old signal stack context
                         specifier.

     DESCRIPTION
          Sigstack is used to install a new signal stack context and
          retrieve the previous signal stack context.  A new signal
          stack context is optionally installed using the
          <new_signal_stack> parameter.  If <new_signal_stack> is
          NULL, the signal stack context remains unchanged.
          Otherwise, <new_signal_stack> is installed.  The previous
          signal stack context may be obtained by the
          <old_signal_stack> parameter.  If <old_signal_stack> is
          NULL, the previous signal stack context is not returned.
          Otherwise, the previous signal stack context information is
          stored in the location pointed to by <old_signal_stack>.

          A signal stack is an alternate execution stack on which
          signals are processed.  The signal stack context consists of
          two components:  the address of the base of the signal stack
          (ss_sp) and an indication as to whether the process is
          currently executing on the signal stack (ss_onstack).

          When a signal's action is `catch' and its signal stack
          choice specifies the signal stack, the system checks to see
          if the process is currently executing on the signal 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.

          Signal stacks do not increase automatically, as is done for
          the normal stack.  If the stack overflows unpredictable
          results may occur.

          Sigstack will fail and the signal stack context will be
          unchanged if an error occurs.



     Licensed material--property of copyright holder(s)         Page 1

     sigstack(2)                DG/UX 4.30                 sigstack(2)



     ACCESS CONTROL
          None.

     RETURN VALUE
          0              Completed successfully.


          -1             An error occurred.  Errno is set to indicate
                         the error.

     EXCEPTIONS
          Errno may be set to the following error code:


          EFAULT         Either <new_signal_stack> or
                         <old_signal_stack> points to memory which is
                         not a valid part of the process address
                         space.  The validity of the signal stack is
                         not checked.

     SEE ALSO
          The related system call:  sigvec.
          The related manual section:  setjmp(3).
































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