.\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH pthread_cleanup_push_defer_np 3 2024-05-02 "Linux man-pages 6.9.1"
.SH NAME
pthread_cleanup_push_defer_np, pthread_cleanup_pop_restore_np \- push and pop
thread cancelation clean-up handlers while saving cancelability type
.SH LIBRARY
POSIX threads library
.RI ( libpthread ", " \-lpthread )
.SH SYNOPSIS
.nf
.B #include <pthread.h>
.P
.BI "void pthread_cleanup_push_defer_np(void (*" routine ")(void *), void *" arg );
.BI "void pthread_cleanup_pop_restore_np(int " execute );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR pthread_cleanup_push_defer_np (),
.BR pthread_cleanup_pop_defer_np ():
.nf
    _GNU_SOURCE
.fi
.SH DESCRIPTION
These functions are the same as
.BR pthread_cleanup_push (3)
and
.BR pthread_cleanup_pop (3),
except for the differences noted on this page.
.P
Like
.BR pthread_cleanup_push (3),
.BR pthread_cleanup_push_defer_np ()
pushes
.I routine
onto the thread's stack of cancelation clean-up handlers.
In addition, it also saves the thread's current cancelability type,
and sets the cancelability type to "deferred" (see
.BR pthread_setcanceltype (3));
this ensures that cancelation clean-up will occur
even if the thread's cancelability type was "asynchronous"
before the call.
.P
Like
.BR pthread_cleanup_pop (3),
.BR pthread_cleanup_pop_restore_np ()
pops the top-most clean-up handler from the thread's
stack of cancelation clean-up handlers.
In addition, it restores the thread's cancelability
type to its value at the time of the matching
.BR pthread_cleanup_push_defer_np ().
.P
The caller must ensure that calls to these
functions are paired within the same function,
and at the same lexical nesting level.
Other restrictions apply, as described in
.BR pthread_cleanup_push (3).
.P
This sequence of calls:
.P
.in +4n
.EX
pthread_cleanup_push_defer_np(routine, arg);
pthread_cleanup_pop_restore_np(execute);
.EE
.in
.P
is equivalent to (but shorter and more efficient than):
.P
.\" As far as I can see, LinuxThreads reverses the two substeps
.\" in the push and pop below.
.in +4n
.EX
int oldtype;
\&
pthread_cleanup_push(routine, arg);
pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldtype);
\&...
pthread_setcanceltype(oldtype, NULL);
pthread_cleanup_pop(execute);
.EE
.in
.SH STANDARDS
GNU;
hence the suffix "_np" (nonportable) in the names.
.SH HISTORY
glibc 2.0
.SH SEE ALSO
.BR pthread_cancel (3),
.BR pthread_cleanup_push (3),
.BR pthread_setcancelstate (3),
.BR pthread_testcancel (3),
.BR pthreads (7)