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@aber.ac.uk>
19#   Copyright (c) 2010 Diego Elio Petteno` <flameeyes@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 15
48
49#   Define m4_ifblank and m4_ifnblank macros from introduced in
50#   autotools 2.64 m4sugar.m4 if using an earlier autotools.
51
52ifdef([m4_ifblank], [], [
53    m4_define([m4_ifblank],
54    [m4_if(m4_translit([[$1]], [ ][	][
55]), [], [$2], [$3])])
56    ])
57
58ifdef([m4_ifnblank], [], [
59    m4_define([m4_ifnblank],
60    [m4_if(m4_translit([[$1]], [ ][	][
61]), [], [$3], [$2])])
62    ])
63
64AC_DEFUN([AX_TLS], [
65  AC_MSG_CHECKING([for thread local storage (TLS) class])
66  AC_CACHE_VAL([ac_cv_tls],
67   [for ax_tls_keyword in thread_local _Thread_local __thread '__declspec(thread)' none; do
68       AS_CASE([$ax_tls_keyword],
69          [none], [ac_cv_tls=none ; break],
70          [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
71              [#include <stdlib.h>],
72              [static  $ax_tls_keyword  int bar;]
73            )],
74            [ac_cv_tls=$ax_tls_keyword ; break],
75            [ac_cv_tls=none]
76          )]
77        )
78    done ]
79  )
80  AC_MSG_RESULT([$ac_cv_tls])
81
82  AS_IF([test "$ac_cv_tls" != "none"],
83    [AC_DEFINE_UNQUOTED([TLS],[$ac_cv_tls],[If the compiler supports a TLS storage class, define it to that here])
84     m4_ifnblank([$1],[$1],[[:]])],
85    [m4_ifnblank([$2],[$2],[[:]])])
86])
87