1# ===========================================================================
2#   Modified from https://www.gnu.org/software/autoconf-archive/ax_add_fortify_source.html
3# ===========================================================================
4#
5# SYNOPSIS
6#
7#   AX_ADD_FORTIFY_SOURCE
8#
9# DESCRIPTION
10#
11#   Check whether -D_FORTIFY_SOURCE=2 can be added to CFLAGS without macro
12#   redefinition warnings. Some distributions (such as Gentoo Linux) enable
13#   _FORTIFY_SOURCE globally in their compilers, leading to unnecessary
14#   warnings in the form of
15#
16#     <command-line>:0:0: error: "_FORTIFY_SOURCE" redefined [-Werror]
17#     <built-in>: note: this is the location of the previous definition
18#
19#   which is a problem if -Werror is enabled. This macro checks whether
20#   _FORTIFY_SOURCE is already defined, and if not, adds -D_FORTIFY_SOURCE=2
21#   to CFLAGS.
22#
23# LICENSE
24#
25#   Copyright (c) 2017 David Seifert <soap@gentoo.org>
26#
27#   Copying and distribution of this file, with or without modification, are
28#   permitted in any medium without royalty provided the copyright notice
29#   and this notice are preserved.  This file is offered as-is, without any
30#   warranty.
31
32#serial 1
33
34AC_DEFUN([AX_ADD_FORTIFY_SOURCE],[
35    AC_MSG_CHECKING([whether to add -D_FORTIFY_SOURCE=2 to CFLAGS])
36    AC_LINK_IFELSE([
37        AC_LANG_SOURCE(
38            [[
39                int main() {
40                #ifndef _FORTIFY_SOURCE
41                    return 0;
42                #else
43                    this_is_an_error;
44                #endif
45                }
46            ]]
47        )], [
48            AC_MSG_RESULT([yes])
49            CFLAGS="$CFLAGS -D_FORTIFY_SOURCE=2"
50        ], [
51            AC_MSG_RESULT([no])
52    ])
53])
54