# ===========================================================================

#          https://www.gnu.org/software/autoconf-archive/ax_tls.html

# ===========================================================================

#

# SYNOPSIS

#

#   AX_TLS([action-if-found], [action-if-not-found])

#

# DESCRIPTION

#

#   Provides a test for the compiler support of thread local storage (TLS)

#   extensions. Defines TLS if it is found. Currently knows about C++11,

#   GCC/ICC, and MSVC. I think SunPro uses the same as GCC, and Borland

#   apparently supports either.

#

# LICENSE

#

#   Copyright (c) 2008 Alan Woodland <ajw05@aber.ac.uk>

#   Copyright (c) 2010 Diego Elio Petteno` <flameeyes@gmail.com>

#

#   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/>.

#

#   As a special exception, the respective Autoconf Macro's copyright owner

#   gives unlimited permission to copy, distribute and modify the configure

#   scripts that are the output of Autoconf when processing the Macro. You

#   need not follow the terms of the GNU General Public License when using

#   or distributing such scripts, even though portions of the text of the

#   Macro appear in them. The GNU General Public License (GPL) does govern

#   all other use of the material that constitutes the Autoconf Macro.

#

#   This special exception to the GPL applies to versions of the Autoconf

#   Macro released by the Autoconf Archive. When you make and distribute a

#   modified version of the Autoconf Macro, you may extend this special

#   exception to the GPL to apply to your modified version as well.

#serial 14

AC_DEFUN([AX_TLS], [

  AC_MSG_CHECKING([for thread local storage (TLS) class])

  AC_CACHE_VAL([ac_cv_tls],

   [for ax_tls_keyword in thread_local _Thread_local __thread '__declspec(thread)' none; do

       AS_CASE([$ax_tls_keyword],

          [none], [ac_cv_tls=none ; break],

          [AC_TRY_COMPILE(

              [#include <stdlib.h>

               static void

               foo(void) {

               static ] $ax_tls_keyword [ int bar;

               exit(1);

               }],

               [],

               [ac_cv_tls=$ax_tls_keyword ; break],

               ac_cv_tls=none

           )])

    done

  ])

  AC_MSG_RESULT([$ac_cv_tls])

  AS_IF([test "$ac_cv_tls" != "none"],

    [AC_DEFINE_UNQUOTED([TLS],[$ac_cv_tls],[If the compiler supports a TLS storage class define it to that here])

     m4_ifnblank([$1],[$1])],

    [m4_ifnblank([$2],[$2])])

])