[PATCH 1/3] build: deal with newer glibc vs. FORTIFY_SOURCE

[Eric Blake]

Recent glibc (for whatever stupid reason) decided to issue a #warning
when FORTIFY_SOURCE is requested but not possible, due to compilation
without optimization.  But when debugging sources, we don't want our
use of -Werror to kill compilation just because glibc wants to be
chatty; when debugging, we don't care about source fortification.

* configure.ac (FORTIFY_SOURCE): Make conditional on optimization.

Signed-off-by: Eric Blake <address@hidden>
---
 ChangeLog    |    7 ++++++-
 configure.ac |   11 ++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 4908b5e..c8e1a72 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2012-06-25  Eric Blake  <address@hidden>
+
+       build: deal with newer glibc vs. FORTIFY_SOURCE
+       * configure.ac (FORTIFY_SOURCE): Make conditional on optimization.
+
 2011-05-02  Eric Blake  <address@hidden>

        build: pick up latest gnulib fixes
@@ -5316,7 +5321,7 @@ Mon Jan 22 21:08:52 1990  Rene' Seindal (seindal at 
diku.dk)
        coding: utf-8
        End:

-       Copyright (C) 1990-1994, 2000-2001, 2003, 2005-2011 Free Software
+       Copyright (C) 1990-1994, 2000-2001, 2003, 2005-2012 Free Software
        Foundation, Inc.

        Copying and distribution of this file, with or without
diff --git a/configure.ac b/configure.ac
index 17f23e7..8eecef3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,5 +1,5 @@
 # Configure template for GNU M4.           -*-Autoconf-*-
-# Copyright (C) 1991, 1993-1994, 2004-2011 Free Software Foundation,
+# Copyright (C) 1991, 1993-1994, 2004-2012 Free Software Foundation,
 # Inc.
 #
 # This file is part of GNU M4.
@@ -85,8 +85,13 @@ if test "$gl_gcc_warnings" = yes; then

   AC_SUBST([WARN_CFLAGS])

-  AC_DEFINE([_FORTIFY_SOURCE], [2],
-    [enable compile-time and run-time bounds-checking, and some warnings])
+  AH_VERBATIM([FORTIFY_SOURCE],
+  [/* Enable compile-time and run-time bounds-checking, and some warnings,
+      without upsetting newer glibc. */
+   #if defined __OPTIMIZE__ && __OPTIMIZE__
+   # define _FORTIFY_SOURCE 2
+   #endif
+  ])
 fi

 # Tandem/NSK is broken - it has 'long long int' but not
-- 
1.7.10.2