pthread_attr_setguardsize(3) Library Functions Manual pthread_attr_setguardsize(3)
NAME
pthread_attr_setguardsize - Changes the guardsize attribute of the specified thread attributes object.
LIBRARY
DECthreads POSIX 1003.1c Library (libpthread.so)
SYNOPSIS
#include <pthread.h>
int pthread_attr_setguardsize(
pthread_attr_t *attr,
size_t guardsize);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
IEEE Std 1003.1c-1995, POSIX System Application Program Interface
PARAMETERS
Address of the thread attributes object whose guardsize attribute is to be modified. New value for the guardsize attribute of the thread
attributes object specified by attr.
DESCRIPTION
This routine uses the value specified in the guardsize argument to set the guardsize attribute of the thread attributes object specified in
the attr argument.
When creating a thread, use a thread attributes object to specify nondefault values for thread attributes. The guardsize attribute of a
thread attributes object specifies the minimum size (in bytes) of the guard area for the stack of a new thread.
A guard area, with its associated overflow warning area, can help a multithreaded program detect overflow of a thread's stack. A guard
area is a region of no-access memory that DECthreads allocates at the overflow end of the thread's stack, following the thread's overflow
warning area. If any thread attempts to write in the overflow warning area, a stack overflow exception occurs. Your program can catch
this exception and continue processing as long as the thread does not attempt to write in the guard area. When any thread attempts to
access a memory location within the guard area, a memory addressing violation occurs without the possibility of recovery.
A new thread can be created with a default guardsize attribute value. This value is platform dependent, but will always be at least one
"hardware protection unit" (that is, at least one page). For more information, see the platform-specific appendixes of Guide to DEC-
threads.
After this routine is called, due to platform-specific factors DECthreads might reserve a larger guard area for the new thread than was
specified in the guardsize argument. For more information, see the platform-specific appendixes of Guide to DECthreads.
DECthreads allows your program to specify the size of a thread stack's guard area for two reasons: When a thread allocates large data
structures on its stack, a guard area with a size greater than the default size might be required to detect stack overflow. Overflow pro-
tection of a thread's stack can potentially waste system resources, such as for an application that creates a large number of threads that
will never overflow their stacks. Your multithreaded program can conserve system resources by "turning off" a thread's stack guard
area--that is, by specifying a guardsize attribute of zero. If a thread is created using a thread attributes object whose stackaddr
attribute is set (using the pthread_attr_setstackaddr(3) routine), this routine ignores the object's guardsize attribute and provides no
thread stack guard area for the new thread.
RETURN VALUES
If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows:
Successful completion. The argument attr is not a valid thread attributes object, or the argument guardsize contains an invalid value.
ERRORS
None
RELATED INFORMATION
Functions: pthread_attr_init(3), pthread_attr_getguardsize(3), pthread_attr_setstacksize(3), pthread_create(3)
Manuals: Guide to DECthreads and Programmer's Guide delim off
pthread_attr_setguardsize(3)