pthread_attr_setstackaddr Subroutine

Purpose

Sets the value of the stackaddr attribute of a thread attributes object.

Library

Threads Library (libpthreads.a)

Syntax

#include <pthread.h>

int pthread_attr_setstackaddr (attr, stackaddr)
pthread_attr_t *attr;
void *stackaddr;

Description

The pthread_attr_setstackaddr subroutine sets the value of the stackaddr attribute of the thread attributes object attr. This attribute specifies the stack address of a thread created with this attributes object.

Note: The pthread.h header file must be the first included file of each source file using the threads library. Otherwise, the -D_THREAD_SAFE compilation flag should be used, or the cc_r compiler used. In this case, the flag is automatically set.
A Provision has been made in libpthreadsto create guardpages for the user stack internally. This is used for debugging purposes only. By default, it is turned off and can be invoked by exporting the following environment variable: 
AIXTHREAD_GUARDPAGES_FOR_USER_STACK=n (Where n is the decimal number of guard pages.)
Note: Even if it is exported, guard pages will only be constructed if both the stackaddr and stacksize attributes have been set by the caller for the thread. Also, the guard pages and alignment pages will be created out of the user's stack (which will reduce the stack size). If the new stack size after creating guard pages is less than the minimum stack size (PTHREAD_STACK_MIN), then the guard pages will not be constructed.

Parameters

Item Description
attr Specifies the thread attributes object.
stackaddr Specifies the stack address to set. It is a void pointer. The address that needs to be passed is not the beginning of the malloc generated address but the beginning of the stack. For example: 
       stackaddr = malloc(stacksize);
       pthread_attr_setstackaddr(&thread, stackaddr + stacksize);

Return Values

Upon successful completion, 0 is returned. Otherwise, an error code is returned.

Error Codes

The pthread_attr_setstackaddr subroutine is unsuccessful if the following is true:

Item Description
EINVAL The attr parameter is not valid.
ENOSYS The stack address POSIX option is not implemented.