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     pthread_attr_getstack, pthread_attr_setstack, pthread_attr_getstacksize,
     pthread_attr_setstacksize, pthread_attr_getstackaddr,
     pthread_attr_setstackaddr - get and set thread stack attributes

     POSIX Threads Library (libpthread, -lpthread)

     #include <pthread.h>

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

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

     pthread_attr_getstacksize(const pthread_attr_t * restrict attr,
         size_t * restrict stacksize);

     pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize);

     pthread_attr_getstackaddr(const pthread_attr_t * restrict attr,
         void ** restrict stackaddr);

     pthread_attr_setstackaddr(pthread_attr_t *attr, void *stackaddr);

     The pthread_attr_getstack() and pthread_attr_setstack() functions get and
     set, respectively, the thread stack attributes stackaddr and stacksize in
     the attr object.  The remaining four functions behave similarly, but
     instead of getting or setting both stackaddr and stacksize, these get and
     set the values individually.

     The stacksize parameter is defined to be the minimum stack size (in
     bytes) allocated for the thread's stack during the creation of the
     thread.  The stackaddr attribute specifies the location of storage to be
     used for the thread's stack.  All pages within the stack described by
     stackaddr and stacksize should be both readable and writable by the

     The behavior is undefined in all functions if the attr parameter does not
     refer to an attribute object initialized by using pthread_attr_init(3)
     prior to the call.  In addition, undefined behavior may follow if the
     pthread_attr_getstack() function is called before the stackaddr attribute
     has been set.

     The rationale behind these functions is to address cases where an
     application may be used in an environment where the stack of a thread
     must be placed to some particular region of memory.  For the majority of
     applications, this is seldom necessary, and the use of these functions
     should be generally avoided.  At least few potential caveats can be

          There is a certain degree of ambiguity in the POSIX standard with
           respect to thread stack.

          The exact behavior of the functions may vary both across machines
           and operating systems.  In particular, the address specified by
           stackaddr should be suitably aligned.  The system page size, as
           specified by sysconf(3), and the use of posix_memalign(3) may
           guarantee some degree of portability.  Also mmap(2) provides means
           for alignment.

          If the application modifies the stack address, it claims also the
           responsibility of allocating the stack area and guarding it against
           possible stack overflow.  No default guard area will be allocated
           (see pthread_attr_getguardsize(3)).  It may be necessary to
           manually use mprotect(2) in order to define a guard area at the end
           of the allocated stack.

          Moreover, if attr is used to create multiple threads, the stack
           address must be changed by the application between successive calls
           to pthread_create(3).

     If successful, these functions return 0.  Otherwise, an error number is
     returned to indicate the error.

     No errors are defined for the three functions that obtain the stack
     values.  The three functions that set the stack values may fail if:

     [ENOMEM]           There was insufficient memory to complete the

     The pthread_attr_setstacksize() function may additionally fail if:

     [EINVAL]           The specified stacksize is less than PTHREAD_STACK_MIN
                        or exceeds some system-imposed limit.

     pthread_attr(3), pthread_attr_setguardsize(3)

     All described functions conform to IEEE Std 1003.1-2001 ("POSIX.1").
     Note that pthread_attr_getstackaddr() and pthread_attr_setstackaddr()
     were however removed from the specification in the IEEE Std 1003.1-2008
     ("POSIX.1") revision.

NetBSD 9.99                      July 9, 2010                      NetBSD 9.99