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 sigstack(2)							 sigstack(2)
			       TO BE OBSOLETED



 NAME
      sigstack - set and/or get signal stack context

 SYNOPSIS
      #include <&lt&lt&lt;signal.h>&gt&gt&gt;

      int sigstack(
	   struct sigstack *ss,
	   struct sigstack *oss
      );

 DESCRIPTION
      The sigstack() function allows the calling process to indicate to the
      system an area of its address space to be used for processing signals
      received by the process.

      If the ss argument is not a null	pointer, it  must point to a
      sigstack structure. The length of the application-supplied stack must
      be at least SIGSTKSZ bytes. If the alternate signal stack overflows,
      the resulting behavior is undefined.  (See APPLICATION USAGE below.)

	   +  The value of the ss_onstack member indicates whether the
	      process wants the system to use an alternate signal stack when
	      delivering signals.

	   +  The value of the ss_sp member indicates the desired location
	      of the alternate signal stack area in the process' address
	      space.

	   +  If the ss argument is a null pointer, the current alternate
	      signal stack context is not changed.

      If the oss argument is not a null pointer, it points to a sigstack
      structure in in which the current alternate signal stack context is
      placed.  The value stored in the ss_onstack member of oss will be non-
      zero if the process is currently executing on the alternate signal
      stack. If the oss argument is a null pointer, the current alternate
      signal stack context is not returned.

      When a signal's action indicates its handler  should execute  on the
      alternate signal stack (specified by calling sigaction()), the
      implementation checks to see if the process is currently executing on
      that stack. If the process is not currently executing on the alternate
      signal stack, the system arranges a switch to the alternate signal
      stack for the duration of the signal handler's execution.

      After a successful call to one of the exec functions, there are no
      alternate signal stacks in the new process image.

 RETURN VALUE
      Upon successful completion, sigstack() returns  0.  Otherwise, it



 Hewlett-Packard Company	    - 1 -   HP-UX Release 11i: November 2000






 sigstack(2)							 sigstack(2)
			       TO BE OBSOLETED



      returns -1 and sets errno to indicate the error.

 ERRORS
      The sigstack() function will fail if:

	   [EPERM]	  An attempt was made to modify an active stack or
			  an active alternate stack.

 WARNINGS
      In HP-UX release 11.11, use of sigstack() in threads created with
      process contention scope could result in undefined behavior.  This
      function will continue to be reliable in threads created with system
      contention scope.

    Obsolescent Interfaces
      sigstack() is to be obsoleted at a future date.

 APPLICATION USAGE
      A portable application, when being written or rewritten, should use
      sigaltstack() instead of sigstack().

      On some implementations, stack space is automatically extended as
      needed. On those implementations, automatic extension is typically not
      available for an alternate stack. If a signal stack overflows, the
      resulting behavior of the process is undefined.

      The direction of stack growth is not indicated in the historical
      definition of struct sigstack.  The only way to portably establish a
      stack pointer is for the application to determine stack growth
      direction, or to allocate a block of storage and set the stack pointer
      to the middle. The implementation may assume that the size of the
      signal stack is SIGSTKSZ as found in <&lt&lt&lt;signal.h>&gt&gt&gt;.	An implementation
      that would like to specify a signal stack size other than SIGSTKSZ
      should use sigaltstack().

      Programs should not use longjmp() to leave a signal handler that is
      running on a stack established with sigstack().  Doing so may disable
      future use of the signal stack.  For abnormal exit from a signal
      handler, siglongjmp(), setcontext(), or swapcontext() may be used.
      These functions fully support switching from one stack to another.

      The sigstack() function requires the application to have knowledge of
      the underlying system's stack architecture. For this reason,
      sigaltstack() is recommended over this function.

    Threads Considerations
      Each thread may define an alternate signal handling stack.

    LWP (Lightweight Processes) Considerations
      Each LWP may define an alternate signal handling stack.




 Hewlett-Packard Company	    - 2 -   HP-UX Release 11i: November 2000






 sigstack(2)							 sigstack(2)
			       TO BE OBSOLETED



 SEE ALSO
      exec(2), fork(2), setjmp(3C), sigaltstack(2), <signal.h>.

 CHANGE HISTORY
      First released in Issue 4, Version 2.

















































				    - 3 -	  Formatted:  August 2, 2006






 sigstack(2)							 sigstack(2)




			HP-UX EXTENSIONS - TO BE OBSOLETED



 SYNOPSIS
      int sigstack(
	   const struct sigstack *ss,
	   struct sigstack *oss
      );

 DESCRIPTION
      The correct use of sigstack() is hardware dependent, and therefore is
      not portable between different HP-UX implementations.  sigspace() is
      portable between different HP-UX implementations and should be used
      when the application does not need to know where the signal stack is
      located (see sigspace(2)).  sigstack() is provided for compatibility
      with other systems that provide this functionality.  Users should note
      that there is no guarantee that functionality similar to this is even
      possible on some architectures.

      The value stored in the ss_onstack member tells whether the process is
      currently using a signal stack, and if so, the value stored in the
      ss_sp member is the current stack pointer for the stack in use.

 ERRORS
	   [EFAULT]	       Either of ss or oss is not a null pointer and
			       points outside the allocated address space of
			       the process.  The reliable detection of this
			       error is implementation dependent.

 WARNINGS
      Do not use sigstack() in conjunction with sigspace().

      Methods for calculating the required stack size are not well
      developed.

      Leaving the context of a service routine abnormally, such as by
      longjmp() (see setjmp(3C)), might remove the guarantee that the
      ordinary execution of the program does not extend into the guaranteed
      space.  It might also cause the program to lose forever its ability to
      automatically increase the stack size, causing the program to be
      limited to the guaranteed space.

      Stack addresses grow from low addresses to high addresses; therefore
      the signal stack address provided to sigstack(2) should point to the
      beginning of the space to be used for the signal stack.  This address
      should be aligned to an eight-byte boundary.

    Obsolescent Interfaces
      sigstack() is to be obsoleted at a future date.




 Hewlett-Packard Company	    - 1 -   HP-UX Release 11i: November 2000






 sigstack(2)							 sigstack(2)




 AUTHOR
      sigstack() was developed by HP and the University of California,
      Berkeley.

 SEE ALSO
      sigspace(2), setjmp(3C).
















































 Hewlett-Packard Company	    - 2 -   HP-UX Release 11i: November 2000