pthread_attr_setguardsize()

Set the thread guardsize attribute

Synopsis:

#include <pthread.h>

int pthread_attr_setguardsize( 
             pthread_attr_t* attr,
             size_t guardsize );

Description:

The pthread_attr_setguardsize() function sets the value of the thread guardsize attribute to guardsize in the attribute structure attr.

If guardsize is 0, threads created with attr have no guard area; otherwise, a guard area of at least guardsize bytes is provided. The default guardsize can be found using the _SC_PAGESIZE constant in a call to sysconf().

The guardsize attribute controls the size of the guard area for the thread's stack. This guard area helps protect against stack overflows; guardsize bytes of extra memory is allocated at the overflow end of the stack. If a thread overflows into this buffer it receives a SIGSEGV signal.

The guardsize attribute is provided because:

Stack overflow protection can waste system resources. An application that creates many threads can save system resources by turning off guard areas if it trusts its threads not to overflow the stack.
When threads allocate large objects on the stack, a large guardsize is required to detect stack overflows.

Returns:

EOK: Success.
EINVAL: Invalid pointer, attr, to a pthread_attr_t structure, or guardsize is invalid.

Classification:

Standard Unix

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Yes
Thread	Yes

Caveats:

If the caller is providing a stack (using attr's stackaddr attribute; see pthread_attr_setstackaddr()), the guardsize is ignored and there's no stack overflow protection for that thread.

The guardsize argument is completely ignored when using a physical mode memory manager.