'\" et
.TH PTHREAD_ATTR_GETSTACK "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
pthread_attr_getstack,
pthread_attr_setstack
\(em get and set stack attributes
.SH SYNOPSIS
.LP
.nf
#include <pthread.h>
.P
int pthread_attr_getstack(const pthread_attr_t *restrict \fIattr\fP,
    void **restrict \fIstackaddr\fP, size_t *restrict \fIstacksize\fP);
int pthread_attr_setstack(pthread_attr_t *\fIattr\fP, void *\fIstackaddr\fP,
    size_t \fIstacksize\fP);
.fi
.SH DESCRIPTION
The
\fIpthread_attr_getstack\fR()
and
\fIpthread_attr_setstack\fR()
functions, respectively, shall get and set the thread creation stack
attributes
.IR stackaddr
and
.IR stacksize
in the
.IR attr
object.
.P
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
.IR stackaddr ,
and the size of the storage shall be
.IR stacksize
bytes. The
.IR stacksize
shall be at least
{PTHREAD_STACK_MIN}.
The
\fIpthread_attr_setstack\fR()
function may fail with
.BR [EINVAL] 
if
.IR stackaddr
does not meet implementation-defined alignment requirements.
All pages within the stack described by
.IR stackaddr
and
.IR stacksize
shall be both readable and writable by the thread.
.P
If the
\fIpthread_attr_getstack\fR()
function is called before the
.IR stackaddr
attribute has been set, the behavior is unspecified.
.P
The behavior is undefined if the value specified by the
.IR attr
argument to
\fIpthread_attr_getstack\fR()
or
\fIpthread_attr_setstack\fR()
does not refer to an initialized thread attributes object.
.SH "RETURN VALUE"
Upon successful completion, these functions shall return a value of 0;
otherwise, an error number shall be returned to indicate the error.
.P
The
\fIpthread_attr_getstack\fR()
function shall store the stack attribute values in
.IR stackaddr
and
.IR stacksize
if successful.
.SH ERRORS
.P
The
\fIpthread_attr_setstack\fR()
function shall fail if:
.TP
.BR EINVAL
The value of
.IR stacksize
is less than
{PTHREAD_STACK_MIN}
or exceeds an implementation-defined limit.
.P
The
\fIpthread_attr_setstack\fR()
function may fail if:
.TP
.BR EINVAL
The value of
.IR stackaddr
does not have proper alignment to be used as a stack, or ((\c
.BR "char *" )\c
.IR stackaddr
+
.IR stacksize )
lacks proper alignment.
.TP
.BR EACCES
The stack page(s) described by
.IR stackaddr
and
.IR stacksize
are not both readable and writable by the thread.
.P
These functions shall not return an error code of
.BR [EINTR] .
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "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.
.P
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\(hy64,
``overflow'' might mean that two separate stack pointers allocated
within the region will overlap somewhere in the middle of the region.
.P
After a successful call to
\fIpthread_attr_setstack\fR(),
the storage area specified by the
.IR stackaddr
parameter is under the control of the implementation, as described in
.IR "Section 2.9.8" ", " "Use of Application-Managed Thread Stacks".
.P
The specification of the
.IR 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
.IR stackaddr .
Applications cannot assume that a buffer obtained from
\fImalloc\fR()
is suitably aligned. Note that although the
.IR stacksize
value passed to
\fIpthread_attr_setstack\fR()
must satisfy alignment requirements, the same is not true for
\fIpthread_attr_setstacksize\fR()
where the implementation must increase the specified size if
necessary to achieve the proper alignment.
.SH RATIONALE
If an implementation detects that the value specified by the
.IR attr
argument to
\fIpthread_attr_getstack\fR()
or
\fIpthread_attr_setstack\fR()
does not refer to an initialized thread attributes object, it is
recommended that the function should fail and report an
.BR [EINVAL] 
error.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.ad l
.IR "\fIpthread_attr_destroy\fR\^(\|)",
.IR "\fIpthread_attr_getdetachstate\fR\^(\|)",
.IR "\fIpthread_attr_getstacksize\fR\^(\|)",
.IR "\fIpthread_create\fR\^(\|)"
.ad b
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<limits.h>\fP",
.IR "\fB<pthread.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .