'\" t
.\" Copyright (c) 2016 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH pthread_getattr_default_np 3 2023-03-30 "Linux man-pages 6.04"
.SH NAME
pthread_getattr_default_np, pthread_setattr_default_np, \-
get or set default thread-creation attributes
.SH LIBRARY
POSIX threads library
.RI ( libpthread ", " \-lpthread )
.SH SYNOPSIS
.nf
.BR "#define _GNU_SOURCE" "             /* See feature_test_macros(7) */"
.B #include <pthread.h>
.PP
.BI "int pthread_getattr_default_np(pthread_attr_t *" attr );
.BI "int pthread_setattr_default_np(const pthread_attr_t *" attr );
.fi
.SH DESCRIPTION
The
.BR pthread_setattr_default_np ()
function sets the default attributes used for creation of a new
thread\[em]that is, the attributes that are used when
.BR pthread_create (3)
is called with a second argument that is NULL.
The default attributes are set using the attributes supplied in
.IR *attr ,
a previously initialized thread attributes object.
Note the following details about the supplied attributes object:
.IP \[bu] 3
The attribute settings in the object must be valid.
.IP \[bu]
The
.I stack address
attribute must not be set in the object.
.IP \[bu]
Setting the
.I stack size
attribute to zero means leave the default stack size unchanged.
.PP
The
.BR pthread_getattr_default_np ()
function initializes the thread attributes object referred to by
.I attr
so that it contains the default attributes used for thread creation.
.SH ERRORS
.TP
.B EINVAL
.RB ( pthread_setattr_default_np ())
One of the attribute settings in
.I attr
is invalid, or the stack address attribute is set in
.IR attr .
.TP
.B ENOMEM
.\" Can happen (but unlikely) while trying to allocate memory for cpuset
.RB ( pthread_setattr_default_np ())
Insufficient memory.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR pthread_getattr_default_np (),
.BR pthread_setattr_default_np ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH STANDARDS
GNU;
hence the suffix "_np" (nonportable) in their names.
.SH HISTORY
glibc 2.18.
.SH EXAMPLES
The program below uses
.BR pthread_getattr_default_np ()
to fetch the default thread-creation attributes and then displays
various settings from the returned thread attributes object.
When running the program, we see the following output:
.PP
.in +4n
.EX
$ \fB./a.out\fP
Stack size:          8388608
Guard size:          4096
Scheduling policy:   SCHED_OTHER
Scheduling priority: 0
Detach state:        JOINABLE
Inherit scheduler:   INHERIT
.EE
.in
.SS Program source
\&
.\" SRC BEGIN (pthread_getattr_default_np.c)
.EX
#define _GNU_SOURCE
#include <err.h>
#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

static void
display_pthread_attr(pthread_attr_t *attr)
{
    int s;
    size_t stacksize;
    size_t guardsize;
    int policy;
    struct sched_param schedparam;
    int detachstate;
    int inheritsched;

    s = pthread_attr_getstacksize(attr, &stacksize);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getstacksize");
    printf("Stack size:          %zd\en", stacksize);

    s = pthread_attr_getguardsize(attr, &guardsize);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getguardsize");
    printf("Guard size:          %zd\en", guardsize);

    s = pthread_attr_getschedpolicy(attr, &policy);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getschedpolicy");
    printf("Scheduling policy:   %s\en",
           (policy == SCHED_FIFO) ? "SCHED_FIFO" :
           (policy == SCHED_RR) ? "SCHED_RR" :
           (policy == SCHED_OTHER) ? "SCHED_OTHER" : "[unknown]");

    s = pthread_attr_getschedparam(attr, &schedparam);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getschedparam");
    printf("Scheduling priority: %d\en", schedparam.sched_priority);

    s = pthread_attr_getdetachstate(attr, &detachstate);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getdetachstate");
    printf("Detach state:        %s\en",
           (detachstate == PTHREAD_CREATE_DETACHED) ? "DETACHED" :
           (detachstate == PTHREAD_CREATE_JOINABLE) ? "JOINABLE" :
           "???");

    s = pthread_attr_getinheritsched(attr, &inheritsched);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_attr_getinheritsched");
    printf("Inherit scheduler:   %s\en",
           (inheritsched == PTHREAD_INHERIT_SCHED) ? "INHERIT" :
           (inheritsched == PTHREAD_EXPLICIT_SCHED) ? "EXPLICIT" :
           "???");
}

int
main(void)
{
    int s;
    pthread_attr_t attr;

    s = pthread_getattr_default_np(&attr);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_getattr_default_np");

    display_pthread_attr(&attr);

    exit(EXIT_SUCCESS);
}
.EE
.\" SRC END
.SH SEE ALSO
.ad l
.nh
.BR pthread_attr_getaffinity_np (3),
.BR pthread_attr_getdetachstate (3),
.BR pthread_attr_getguardsize (3),
.BR pthread_attr_getinheritsched (3),
.BR pthread_attr_getschedparam (3),
.BR pthread_attr_getschedpolicy (3),
.BR pthread_attr_getscope (3),
.BR pthread_attr_getstack (3),
.BR pthread_attr_getstackaddr (3),
.BR pthread_attr_getstacksize (3),
.BR pthread_attr_init (3),
.BR pthread_create (3),
.BR pthreads (7)