##### http://autoconf-archive.cryp.to/ax_tls.html
#
# SYNOPSIS
#
#   AX_TLS
#
# DESCRIPTION
#
#   Provides a test for the compiler support of thread local storage
#   (TLS) extensions. Defines TLS if it is found. Currently only knows
#   about GCC and MSVC. I think SunPro uses the same as GCC, and
#   Borland apparently supports either.
#
# LAST MODIFICATION
#
#   2007-19-07
#
# COPYLEFT
#
#   Copyright (c) 2007 Alan Woodland <ajw05@aber.ac.uk>
#
#   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 2 of the
#   License, or (at your option) any later version.
#
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#   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.
#
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#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
#   02111-1307, USA.
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AC_DEFUN([AX_TLS], [
  AC_MSG_CHECKING(for thread local storage (TLS) class)
  AC_CACHE_VAL(ac_cv_tls, [
    ax_tls_keywords="__thread __declspec(thread) none"
    for ax_tls_keyword in $ax_tls_keywords; do
       case $ax_tls_keyword in
          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
             )
	  esac
    done
])

  if test "$ac_cv_tls" != "none"; then
    dnl AC_DEFINE([TLS], [], [If the compiler supports a TLS storage class define it to that here])
    AC_DEFINE_UNQUOTED([TLS], $ac_cv_tls, [If the compiler supports a TLS storage class define it to that here])
  fi
  AC_MSG_RESULT($ac_cv_tls)
])