sigspace(2)							System Calls Manual						       sigspace(2)

NAME

       sigspace - assure sufficient signal stack space

SYNOPSIS

DESCRIPTION

       requests additional stack space that is guaranteed to be available for processing signals received by the calling process.

       If  the	value  of stacksize is positive, it specifies the size of a space, in bytes, which the system guarantees to be available when pro-
       cessing a signal.  If the value of stacksize is zero, any guarantee of space is removed.  If the value is negative, the guarantee  is  left
       unchanged; this can be used to interrogate the current guaranteed value.

       When  a	signal's action indicates that its handler should use the guaranteed space (specified with a or call (see bsdproc(3C)), the system
       checks to see if the process is currently using that space.  If the process is not currently using that space, the system arranges for that
       space to be available for the duration of the signal handler's execution.  If that space has already been made available (due to a previous
       signal), no change is made.  Normal stack discipline is resumed when the signal handler first using the guaranteed space is exited.

       The guaranteed space is inherited by child processes resulting from a successful system call, but the guarantee of space is  removed  after
       any system call (see fork(2) and exec(2)).

       The  guaranteed	space  cannot  be increased in size automatically, as is done for the normal stack.  If the stack overflows the guaranteed
       space, the resulting behavior of the process is undefined.

       Guaranteeing space for a stack can interfere with other memory allocation routines in an implementation-dependent manner.

       During normal execution of the program, the system checks for possible overflow of the stack.  Guaranteeing space  might  cause	the  space
       available for normal execution to be reduced.

       Leaving	the context of a service routine abnormally, such as by (see setjmp(3C)), removes the guarantee that the ordinary execution of the
       program will 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.

RETURN VALUE

       Upon successful completion, returns the size of the former guaranteed space.  Otherwise, it returns -1 and sets to indicate the error.

ERRORS

       fails and the guaranteed amount of space remains unchanged if the following occurs:

	      [ENOMEM]		  The  requested  space  cannot  be  guaranteed,  either because of hardware limitations or because some software-
				  imposed limit would be exceeded.

WARNINGS

       The guaranteed space is allocated using malloc(3C).  This use might interfere with other heap management mechanisms.

       Methods for calculating the required size are not well developed.

       Do not use in conjunction with the facilities described under sigset(3C).

       Do not use in conjunction with sigstack(2).

       In HP-UX release 11.11, use of 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.

APPLICATION USAGE

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

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

AUTHOR

       was developed by HP.

SEE ALSO

       sigaction(2), sigstack(2), malloc(3C), setjmp(3C).

																       sigspace(2)