HP-UX Reference (11i v1 00/12) - 2 System Calls (vol 5)
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STANDARD Printed by: Nora Chuang [nchuang] STANDARD
/build/1111/BRICK/man2/!!!intro.2
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s
sigstack(2) sigstack(2)
(TO BE OBSOLETED)
NAME
sigstack - set and/or get signal stack context
SYNOPSIS
#include <signal.h>
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 cal-
ling
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 returns −1 and sets errno to indi-
cate 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 sig-
stack()
.
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 result-
ing 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
Section 2−−364 − 1 − HP-UX Release 11i: December 2000
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