From 05609d5b4b02e87c17c01a0ebb9fc2e05b799d90 Mon Sep 17 00:00:00 2001
From: Erik de Castro Lopo <erikd@mega-nerd.com>
Date: Tue, 5 Mar 2013 21:53:18 +1100
Subject: [PATCH] configure.ac : Add hardening compile options.

Extra compile options are detected at configure time with new
XIPH_ADD_*FLAGS m4 macros.

Options enabled include -Wextra, -D_FORTIFY_SOURCE=2 and stack
protection.
---
 configure.ac       |  4 ++++
 m4/add_cflags.m4   | 18 ++++++++++++++++++
 m4/add_cxxflags.m4 | 19 +++++++++++++++++++
 3 files changed, 41 insertions(+)
 create mode 100644 m4/add_cflags.m4
 create mode 100644 m4/add_cxxflags.m4

diff --git a/configure.ac b/configure.ac
index ac35de22..b99f4027 100644
--- a/configure.ac
+++ b/configure.ac
@@ -356,6 +356,10 @@ fi
 
 XIPH_GCC_VERSION
 
+XIPH_ADD_CFLAGS([-Wextra])
+XIPH_ADD_CFLAGS([-D_FORTIFY_SOURCE=2])
+XIPH_ADD_CFLAGS([-fstack-protector --param ssp-buffer-size=4])
+
 if test x$ac_cv_c_compiler_gnu = xyes ; then
 	if test x$enable_gcc_werror = "xyes" ; then
 		CFLAGS="-Wall -Wextra -Werror $CFLAGS"
diff --git a/m4/add_cflags.m4 b/m4/add_cflags.m4
new file mode 100644
index 00000000..08f4a409
--- /dev/null
+++ b/m4/add_cflags.m4
@@ -0,0 +1,18 @@
+dnl @synopsis XIPH_ADD_CFLAGS
+dnl
+dnl Add the given option to CFLAGS, if it doesn't break the compiler
+
+AC_DEFUN([XIPH_ADD_CFLAGS],
+[AC_MSG_CHECKING([if $CC accepts $1])
+	ac_add_cflags__old_cflags="$CFLAGS"
+	CFLAGS="$1"
+	AC_TRY_LINK([
+			#include <stdio.h>
+			],
+		[puts("Hello, World!"); return 0;],
+		AC_MSG_RESULT([yes])
+			CFLAGS="$ac_add_cflags__old_cflags $1",
+		AC_MSG_RESULT([no])
+			CFLAGS="$ac_add_cflags__old_cflags"
+		)
+])# XIPH_ADD_CFLAGS
diff --git a/m4/add_cxxflags.m4 b/m4/add_cxxflags.m4
new file mode 100644
index 00000000..8197dc2d
--- /dev/null
+++ b/m4/add_cxxflags.m4
@@ -0,0 +1,19 @@
+dnl @synopsis XIPH_ADD_CXXFLAGS
+dnl
+dnl Add the given option to CXXFLAGS, if it doesn't break the compiler
+
+AC_DEFUN([XIPH_ADD_CXXFLAGS],
+[AC_MSG_CHECKING([if $CXX accepts $1])
+	AC_LANG_ASSERT([C++])
+	ac_add_cxxflags__old_cxxflags="$CXXFLAGS"
+	CXXFLAGS="$1"
+	AC_TRY_LINK([
+			#include <cstdio>
+			],
+		[puts("Hello, World!"); return 0;],
+		AC_MSG_RESULT([yes])
+			CXXFLAGS="$ac_add_cxxflags__old_cxxflags $1",
+		AC_MSG_RESULT([no])
+			CXXFLAGS="$ac_add_cxxflags__old_cxxflags"
+		)
+])# XIPH_ADD_CXXFLAGS