pthread_attr_setguardsize(3C) Syntax

#include <pthread.h> 
int pthread_attr_setguardsize(pthread_attr_t *attr, size_t guardsize);

The guardsize attribute is provided to the application for two reasons:

• Overflow protection can potentially result in wasted system resources. When your application creates a large number of threads, and you know that the threads will never overflow their stack, you can turn off guard areas. By turning off guard areas, you can conserve system resources.

• When threads allocate large data structures on stack, a large guard area might be needed to detect stack overflow.

The guardsize argument provides protection against overflow of the stack pointer. If a thread's stack is created with guard protection, the implementation allocates extra memory at the overflow end of the stack. This extra memory acts as a buffer against stack overflow of the stack pointer. If an application overflows into this buffer an error results, possibly in a SIGSEGV signal being delivered to the thread.

If guardsize is zero, a guard area is not provided for threads that are created with attr. If guardsize is greater than zero, a guard area of at least size guardsize bytes is provided for each thread created with attr. By default, a thread has an implementation-defined, nonzero guard area.

A conforming implementation is permitted to round up the value contained in guardsize to a multiple of the configurable system variable PAGESIZE . See PAGESIZE in sys/mman.h. If an implementation rounds up the value of guardsize to a multiple of PAGESIZE, a call to pthread_attr_getguardsize() that specifies attr stores, in guardsize, the guard size specified in the previous call to pthread_attr_setguardsize().