HP-UX Reference (11i v2 07/12) - 2 System Calls (vol 5)

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sigstack(2) sigstack(2)

(TO BE OBSOLETED)

WARNINGS

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

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. An application can assume that the size of the sig-

nal stack is

SIGSTKSZ. To specify a signal stack size other than

SIGSTKSZ, use the sigaltstack()

function.

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.

In HP-UX release 11.i, 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

the signal stack is

SIGSTKSZ as found in <signal.h> . 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() ,orswapcontext()

may be used. These functions fully

support switching from one stack to another.

Threads Considerations

Each thread (with system contention scope) may deﬁne an alternate signal handling stack.

AUTHOR

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