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      1 # ===========================================================================
      2 #          https://www.gnu.org/software/autoconf-archive/ax_tls.html
      3 # ===========================================================================
      4 #
      5 # SYNOPSIS
      6 #
      7 #   AX_TLS([action-if-found], [action-if-not-found])
      8 #
      9 # DESCRIPTION
     10 #
     11 #   Provides a test for the compiler support of thread local storage (TLS)
     12 #   extensions. Defines TLS if it is found. Currently knows about C++11,
     13 #   GCC/ICC, and MSVC. I think SunPro uses the same as GCC, and Borland
     14 #   apparently supports either.
     15 #
     16 # LICENSE
     17 #
     18 #   Copyright (c) 2008 Alan Woodland <ajw05 (a] aber.ac.uk>
     19 #   Copyright (c) 2010 Diego Elio Petteno` <flameeyes (a] gmail.com>
     20 #
     21 #   This program is free software: you can redistribute it and/or modify it
     22 #   under the terms of the GNU General Public License as published by the
     23 #   Free Software Foundation, either version 3 of the License, or (at your
     24 #   option) any later version.
     25 #
     26 #   This program is distributed in the hope that it will be useful, but
     27 #   WITHOUT ANY WARRANTY; without even the implied warranty of
     28 #   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
     29 #   Public License for more details.
     30 #
     31 #   You should have received a copy of the GNU General Public License along
     32 #   with this program. If not, see <https://www.gnu.org/licenses/>.
     33 #
     34 #   As a special exception, the respective Autoconf Macro's copyright owner
     35 #   gives unlimited permission to copy, distribute and modify the configure
     36 #   scripts that are the output of Autoconf when processing the Macro. You
     37 #   need not follow the terms of the GNU General Public License when using
     38 #   or distributing such scripts, even though portions of the text of the
     39 #   Macro appear in them. The GNU General Public License (GPL) does govern
     40 #   all other use of the material that constitutes the Autoconf Macro.
     41 #
     42 #   This special exception to the GPL applies to versions of the Autoconf
     43 #   Macro released by the Autoconf Archive. When you make and distribute a
     44 #   modified version of the Autoconf Macro, you may extend this special
     45 #   exception to the GPL to apply to your modified version as well.
     46 
     47 #serial 14
     48 
     49 AC_DEFUN([AX_TLS], [
     50   AC_MSG_CHECKING([for thread local storage (TLS) class])
     51   AC_CACHE_VAL([ac_cv_tls],
     52    [for ax_tls_keyword in thread_local _Thread_local __thread '__declspec(thread)' none; do
     53        AS_CASE([$ax_tls_keyword],
     54           [none], [ac_cv_tls=none ; break],
     55           [AC_TRY_COMPILE(
     56               [#include <stdlib.h>
     57                static void
     58                foo(void) {
     59                static ] $ax_tls_keyword [ int bar;
     60                exit(1);
     61                }],
     62                [],
     63                [ac_cv_tls=$ax_tls_keyword ; break],
     64                ac_cv_tls=none
     65            )])
     66     done
     67   ])
     68   AC_MSG_RESULT([$ac_cv_tls])
     69 
     70   AS_IF([test "$ac_cv_tls" != "none"],
     71     [AC_DEFINE_UNQUOTED([TLS],[$ac_cv_tls],[If the compiler supports a TLS storage class define it to that here])
     72      m4_ifnblank([$1],[$1])],
     73     [m4_ifnblank([$2],[$2])])
     74 ])
     75