1# SPDX-License-Identifier: GPL-3.0-or-later WITH Autoconf-exception-3.0
2#
3# ===========================================================================
4#          https://www.gnu.org/software/autoconf-archive/ax_tls.html
5# ===========================================================================
6#
7# SYNOPSIS
8#
9#   AX_TLS([action-if-found], [action-if-not-found])
10#
11# DESCRIPTION
12#
13#   Provides a test for the compiler support of thread local storage (TLS)
14#   extensions. Defines TLS if it is found. Currently knows about C++11,
15#   GCC/ICC, and MSVC. I think SunPro uses the same as GCC, and Borland
16#   apparently supports either.
17#
18# LICENSE
19#
20#   Copyright (c) 2008 Alan Woodland <ajw05@aber.ac.uk>
21#   Copyright (c) 2010 Diego Elio Petteno` <flameeyes@gmail.com>
22#
23#   This program is free software: you can redistribute it and/or modify it
24#   under the terms of the GNU General Public License as published by the
25#   Free Software Foundation, either version 3 of the License, or (at your
26#   option) any later version.
27#
28#   This program is distributed in the hope that it will be useful, but
29#   WITHOUT ANY WARRANTY; without even the implied warranty of
30#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
31#   Public License for more details.
32#
33#   You should have received a copy of the GNU General Public License along
34#   with this program. If not, see <https://www.gnu.org/licenses/>.
35#
36#   As a special exception, the respective Autoconf Macro's copyright owner
37#   gives unlimited permission to copy, distribute and modify the configure
38#   scripts that are the output of Autoconf when processing the Macro. You
39#   need not follow the terms of the GNU General Public License when using
40#   or distributing such scripts, even though portions of the text of the
41#   Macro appear in them. The GNU General Public License (GPL) does govern
42#   all other use of the material that constitutes the Autoconf Macro.
43#
44#   This special exception to the GPL applies to versions of the Autoconf
45#   Macro released by the Autoconf Archive. When you make and distribute a
46#   modified version of the Autoconf Macro, you may extend this special
47#   exception to the GPL to apply to your modified version as well.
48
49#serial 15
50
51AC_DEFUN([AX_TLS], [
52  AC_MSG_CHECKING([for thread local storage (TLS) class])
53  AC_CACHE_VAL([ac_cv_tls],
54   [for ax_tls_keyword in thread_local _Thread_local __thread '__declspec(thread)' none; do
55       AS_CASE([$ax_tls_keyword],
56          [none], [ac_cv_tls=none ; break],
57          [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
58              [#include <stdlib.h>],
59              [static  $ax_tls_keyword  int bar;]
60            )],
61            [ac_cv_tls=$ax_tls_keyword ; break],
62            [ac_cv_tls=none]
63          )]
64        )
65    done ]
66  )
67  AC_MSG_RESULT([$ac_cv_tls])
68
69  AS_IF([test "$ac_cv_tls" != "none"],
70    [AC_DEFINE_UNQUOTED([TLS],[$ac_cv_tls],[If the compiler supports a TLS storage class, define it to that here])
71     m4_ifnblank([$1],[$1],[[:]])],
72    [m4_ifnblank([$2],[$2],[[:]])])
73])
74