NAME

pthread_attr_getstack, pthread_attr_setstack — get and set stack attributes

SYNOPSIS

[TSA TSS] #include <pthread.h>

int pthread_attr_getstack(const pthread_attr_t *restrict attr,
       void **restrict stackaddr, size_t *restrict stacksize);
int pthread_attr_setstack(pthread_attr_t *attr, void *stackaddr,
       size_t stacksize);

DESCRIPTION

The pthread_attr_getstack() and pthread_attr_setstack() functions, respectively, shall get and set the thread creation stack attributes stackaddr and stacksize in the attr object.

The stack attributes specify the area of storage to be used for the created thread's stack. The base (lowest addressable byte) of the storage shall be stackaddr, and the size of the storage shall be stacksize bytes. The stacksize shall be at least {PTHREAD_STACK_MIN}. The pthread_attr_setstack() function may fail with [EINVAL] if stackaddr does not meet implementation-defined alignment requirements. All pages within the stack described by stackaddr and stacksize shall be both readable and writable by the thread.

If the pthread_attr_getstack() function is called before the stackaddr attribute has been set, the behavior is unspecified.

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

RETURN VALUE

Upon successful completion, these functions shall return a value of 0; otherwise, an error number shall be returned to indicate the error.

The pthread_attr_getstack() function shall store the stack attribute values in stackaddr and stacksize if successful.

ERRORS

The pthread_attr_setstack() function shall fail if:

[EINVAL]

The value of stacksize is less than {PTHREAD_STACK_MIN} or exceeds an implementation-defined limit.

The pthread_attr_setstack() function may fail if:

[EINVAL]

The value of stackaddr does not have proper alignment to be used as a stack, or ((char *)stackaddr + stacksize) lacks proper alignment.

[EACCES]

The stack page(s) described by stackaddr and stacksize are not both readable and writable by the thread.

These functions shall not return an error code of [EINTR].

EXAMPLES

None.

APPLICATION USAGE

These functions are appropriate for use by applications in an environment where the stack for a thread must be placed in some particular region of memory.

While it might seem that an application could detect stack overflow by providing a protected page outside the specified stack region, this cannot be done portably. Implementations are free to place the thread's initial stack pointer anywhere within the specified region to accommodate the machine's stack pointer behavior and allocation requirements. Furthermore, on some architectures, such as the IA-64, "overflow" might mean that two separate stack pointers allocated within the region will overlap somewhere in the middle of the region.

After a successful call to pthread_attr_setstack(), the storage area specified by the stackaddr parameter is under the control of the implementation, as described in 2.9.8 Use of Application-Managed Thread Stacks.

The specification of the stackaddr attribute presents several ambiguities that make portable use of these functions impossible. For example, the standard allows implementations to impose arbitrary alignment requirements on stackaddr. Applications cannot assume that a buffer obtained from malloc() is suitably aligned. Note that although the stacksize value passed to pthread_attr_setstack() must satisfy alignment requirements, the same is not true for pthread_attr_setstacksize() where the implementation must increase the specified size if necessary to achieve the proper alignment.

RATIONALE

If an implementation detects that the value specified by the attr argument to pthread_attr_getstack() or pthread_attr_setstack() does not refer to an initialized thread attributes object, it is recommended that the function should fail and report an [EINVAL] error.

FUTURE DIRECTIONS

None.

SEE ALSO

pthread_attr_destroy, pthread_attr_getdetachstate, pthread_attr_getstacksize, pthread_create

XBD <limits.h>, <pthread.h>

CHANGE HISTORY

First released in Issue 6. Developed as part of the XSI option and brought into the BASE by IEEE PASC Interpretation 1003.1 #101.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC2/D6/83 is applied, updating the APPLICATION USAGE section to refer to 2.9.8 Use of Application-Managed Thread Stacks.

IEEE Std 1003.1-2001/Cor 2-2004, item XSH/TC/D6/84 is applied, updating the ERRORS section to include optional errors for the case when attr refers to an uninitialized thread attribute object.

Issue 7

SD5-XSH-ERN-66 is applied, correcting the use of attr in the [EINVAL] error condition.

Austin Group Interpretation 1003.1-2001 #057 is applied, clarifying the behavior if the function is called before the stackaddr attribute is set.

SD5-XSH-ERN-157 is applied, updating the APPLICATION USAGE section.

The description of the stackaddr attribute is updated in the DESCRIPTION and APPLICATION USAGE sections.

The [EINVAL] error for an uninitialized thread attributes object is removed; this condition results in undefined behavior.