From 804e6190d75f7f0f8eb251c21d05a55ff0f35c12 Mon Sep 17 00:00:00 2001
From: Reinhard Urban <reinhard.urban@nubix.de>
Date: Fri, 6 Jan 2023 10:51:34 +0100
Subject: AX_ADD_FORTIFY_SOURCE: add -D_FORTIFY_SOURCE=3 check

---
 m4/ax_add_fortify_source.m4 | 47 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 3 deletions(-)

(limited to 'm4')

diff --git a/m4/ax_add_fortify_source.m4 b/m4/ax_add_fortify_source.m4
index 7e15312..1266048 100644
--- a/m4/ax_add_fortify_source.m4
+++ b/m4/ax_add_fortify_source.m4
@@ -10,7 +10,7 @@
 #
 #   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
+#   (such as Ubuntu or 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]
@@ -29,7 +29,7 @@
 # LICENSE
 #
 #   Copyright (c) 2017 David Seifert <soap@gentoo.org>
-#   Copyright (c) 2019 Reini Urban <rurban@cpan.org>
+#   Copyright (c) 2019, 2023 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
@@ -42,6 +42,46 @@ AC_DEFUN([AX_ADD_FORTIFY_SOURCE],[
     ac_save_cflags=$CFLAGS
     ac_cwerror_flag=yes
     AX_CHECK_COMPILE_FLAG([-Werror],[CFLAGS="$CFLAGS -Werror"])
+    ax_add_fortify_3_failed=
+    AC_MSG_CHECKING([whether to add -D_FORTIFY_SOURCE=3 to CPPFLAGS])
+    AC_LINK_IFELSE([
+        AC_LANG_PROGRAM([],
+            [[
+                #ifndef _FORTIFY_SOURCE
+                    return 0;
+                #else
+                    _FORTIFY_SOURCE_already_defined;
+                #endif
+            ]]
+        )],
+        AC_LINK_IFELSE([
+            AC_LANG_SOURCE([[
+                #define _FORTIFY_SOURCE 3
+                #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=3"
+            ], [
+              AC_MSG_RESULT([no])
+              CFLAGS=$ac_save_cflags
+              ax_add_fortify_3_failed=1
+            ],
+        ),
+        [
+          AC_MSG_RESULT([no])
+          CFLAGS=$ac_save_cflags
+          ax_add_fortify_3_failed=1
+        ])
+    if test -n "$ax_add_fortify_3_failed"
+    then
     AC_MSG_CHECKING([whether to add -D_FORTIFY_SOURCE=2 to CPPFLAGS])
     AC_LINK_IFELSE([
         AC_LANG_PROGRAM([],
@@ -49,7 +89,7 @@ AC_DEFUN([AX_ADD_FORTIFY_SOURCE],[
                 #ifndef _FORTIFY_SOURCE
                     return 0;
                 #else
-                    this_is_an_error;
+                    _FORTIFY_SOURCE_already_defined;
                 #endif
             ]]
         )],
@@ -77,4 +117,5 @@ AC_DEFUN([AX_ADD_FORTIFY_SOURCE],[
           AC_MSG_RESULT([no])
           CFLAGS=$ac_save_cflags
         ])
+    fi
 ])
-- 
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