@node ax_pthread
@unnumberedsec ax_pthread

@majorheading Synopsis

@smallexample
AX_PTHREAD([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]])
@end smallexample

@majorheading Description

This macro figures out how to build C programs using POSIX threads. It
sets the PTHREAD_LIBS output variable to the threads library and linker
flags, and the PTHREAD_CFLAGS output variable to any special C compiler
flags that are needed. (The user can also force certain compiler
flags/libs to be tested by setting these environment variables.)

Also sets PTHREAD_CC and PTHREAD_CXX to any special C compiler that is
needed for multi-threaded programs (defaults to the value of CC
respectively CXX otherwise). (This is necessary on e.g. AIX to use the
special cc_r/CC_r compiler alias.)

NOTE: You are assumed to not only compile your program with these flags,
but also to link with them as well. For example, you might link with
$PTHREAD_CC $CFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS
$PTHREAD_CXX $CXXFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS

If you are only building threaded programs, you may wish to use these
variables in your default LIBS, CFLAGS, and CC:

@smallexample
  LIBS="$PTHREAD_LIBS $LIBS"
  CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
  CXXFLAGS="$CXXFLAGS $PTHREAD_CFLAGS"
  CC="$PTHREAD_CC"
  CXX="$PTHREAD_CXX"
@end smallexample

In addition, if the PTHREAD_CREATE_JOINABLE thread-attribute constant
has a nonstandard name, this macro defines PTHREAD_CREATE_JOINABLE to
that name (e.g. PTHREAD_CREATE_UNDETACHED on AIX).

Also HAVE_PTHREAD_PRIO_INHERIT is defined if pthread is found and the
PTHREAD_PRIO_INHERIT symbol is defined when compiling with
PTHREAD_CFLAGS.

ACTION-IF-FOUND is a list of shell commands to run if a threads library
is found, and ACTION-IF-NOT-FOUND is a list of commands to run it if it
is not found. If ACTION-IF-FOUND is not specified, the default action
will define HAVE_PTHREAD.

Please let the authors know if this macro fails on any platform, or if
you have any other suggestions or comments. This macro was based on work
by SGJ on autoconf scripts for FFTW (http://www.fftw.org/) (with help
from M. Frigo), as well as ac_pthread and hb_pthread macros posted by
Alejandro Forero Cuervo to the autoconf macro repository. We are also
grateful for the helpful feedback of numerous users.

Updated for Autoconf 2.68 by Daniel Richard G.

@majorheading Source Code

Download the
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_pthread.m4,latest
version of @file{ax_pthread.m4}} or browse
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_pthread.m4,the
macro's revision history}.

@majorheading License

@w{Copyright @copyright{} 2008 Steven G. Johnson @email{stevenj@@alum.mit.edu}} @* @w{Copyright @copyright{} 2011 Daniel Richard G. @email{skunk@@iSKUNK.ORG}} @* @w{Copyright @copyright{} 2019 Marc Stevens @email{marc.stevens@@cwi.nl}}

This program is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at your
option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
Public License for more details.

You should have received a copy of the GNU General Public License along
with this program. If not, see <https://www.gnu.org/licenses/>.

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