pthread_attr_getguardsize¶

Synopsis¶

#include <pthread.h>

int pthread_attr_getguardsize(const pthread_attr_t *restrict attr,
                              size_t *restrict guardsize);

int pthread_attr_setguardsize(pthread_attr_t *attr,
                              size_t guardsize);

Status¶

Implemented

Conformance¶

IEEE Std 1003.1-2017

Description¶

The pthread_attr_getguardsize() function shall get the guardsize attribute in the attr object. This attribute shall be returned in the guardsize parameter.

The pthread_attr_setguardsize() function shall set the guardsize attribute in the attr object. The new value of this attribute shall be obtained from the guardsize parameter. If guardsize is zero, a guard area shall not be provided for threads created with attr. If guardsize is greater than zero, a guard area of at least size guardsize bytes shall be provided for each thread created with attr.

The guardsize attribute controls the size of the guard area for the created thread’s stack. The guardsize attribute 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 as a buffer against stack overflow of the stack pointer. If an application overflows into this buffer an error shall result (possibly in a SIGSEGV signal being delivered to the thread).

A conforming implementation may round up the value contained in guardsize to a multiple of the configurable system variable PAGESIZE. If an implementation rounds up the value of guardsize to a multiple of PAGESIZE, a call to pthread_attr_getguardsize() specifying attr shall store in the guardsize parameter the guard size specified by the previous pthread_attr_setguardsize() function call. Phoenix-RTOS rounds the guard size up to a multiple of the page size when the thread is created.

The default value of the guardsize attribute is implementation-defined. In Phoenix-RTOS it is 0.

If the stackaddr attribute has been set (that is, the caller is allocating and managing its own thread stacks), the guardsize attribute shall be ignored and no protection shall be provided by the implementation. It is the responsibility of the application to manage stack overflow along with stack allocation and management in this case.

The behavior is undefined if the value specified by the attr argument to pthread_attr_getguardsize() or pthread_attr_setguardsize() does not refer to an initialized thread attributes object.

Return value¶

If successful, the pthread_attr_getguardsize() and pthread_attr_setguardsize() functions shall return zero; otherwise, an error number shall be returned to indicate the error.

Errors¶

These functions shall fail if:

EINVAL - The parameter guardsize is invalid.

These functions shall not return an error code of EINTR.

POSIX deviations¶

No POSIX deviations discovered.