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.

NAME

       pthread_attr_getstack, pthread_attr_setstack — get and set stack attributes

SYNOPSIS

       #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].

       The following sections are informative.

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 Section 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()

       The Base Definitions volume of POSIX.1‐2017, <limits.h>, <pthread.h>

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 .

       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 .