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# ===========================================================================
# https://www.gnu.org/software/autoconf-archive/ax_add_fortify_source.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_ADD_FORTIFY_SOURCE
#
# DESCRIPTION
#
# Check whether -D_FORTIFY_SOURCE=2 can be added to CPPFLAGS without macro
# redefinition warnings, other cpp warnings or linker. Some distributions
# (such as Gentoo Linux) enable _FORTIFY_SOURCE globally in their
# compilers, leading to unnecessary warnings in the form of
#
# <command-line>:0:0: error: "_FORTIFY_SOURCE" redefined [-Werror]
# <built-in>: note: this is the location of the previous definition
#
# which is a problem if -Werror is enabled. This macro checks whether
# _FORTIFY_SOURCE is already defined, and if not, adds -D_FORTIFY_SOURCE=2
# to CPPFLAGS.
#
# Newer mingw-w64 msys2 package comes with a bug in
# headers-git-7.0.0.5546.d200317d-1. It broke -D_FORTIFY_SOURCE support,
# and would need -lssp or -fstack-protector. See
# https://github.com/msys2/MINGW-packages/issues/5803. Try to actually
# link it.
#
# LICENSE
#
# Copyright (c) 2017 David Seifert <soap@gentoo.org>
# Copyright (c) 2019 Reini Urban <rurban@cpan.org>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 4
AC_DEFUN([AX_ADD_FORTIFY_SOURCE],[
ac_save_cflags=$CFLAGS
ac_cwerror_flag=yes
AX_CHECK_COMPILE_FLAG([-Werror],[CFLAGS="$CFLAGS -Werror"])
AC_MSG_CHECKING([whether to add -D_FORTIFY_SOURCE=2 to CPPFLAGS])
AC_LINK_IFELSE([
AC_LANG_PROGRAM([],
[[
#ifndef _FORTIFY_SOURCE
return 0;
#else
this_is_an_error;
#endif
]]
)],
AC_LINK_IFELSE([
AC_LANG_SOURCE([[
#define _FORTIFY_SOURCE 2
#include <string.h>
int main() {
char *s = " ";
strcpy(s, "x");
return strlen(s)-1;
}
]]
)],
[
AC_MSG_RESULT([yes])
CFLAGS=$ac_save_cflags
CPPFLAGS="$CPPFLAGS -D_FORTIFY_SOURCE=2"
], [
AC_MSG_RESULT([no])
CFLAGS=$ac_save_cflags
],
),
[
AC_MSG_RESULT([no])
CFLAGS=$ac_save_cflags
])
])
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