# ===========================================================================
#          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 15

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_COMPILE_IFELSE([AC_LANG_PROGRAM(
              [#include <stdlib.h>],
              [static  $ax_tls_keyword  int bar;]
            )],
            [ac_cv_tls=$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],[[:]])])
])