From 5bbe8b009d6daa809f679fd1d25c270abba468b4 Mon Sep 17 00:00:00 2001
From: Robbie Harwood <rharwood@redhat.com>
Date: Wed, 31 Jan 2018 17:52:39 +0100
Subject: [PATCH] Verify flags prior to adding them to CFLAGS, not after

---
 configure.ac | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index b7b5908..4084965 100644
--- a/configure.ac
+++ b/configure.ac
@@ -8,8 +8,11 @@ m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],
     [AC_GNU_SOURCE])
 
 AC_PROG_CC_C99
+
 for flag in -Wall -Wextra; do
-  AC_TRY_COMPILE([], [return 0;], [CFLAGS="$CFLAGS $flag"],)
+  OLD_CFLAGS=$CFLAGS
+  CFLAGS="$CFLAGS $flag"
+  AC_TRY_COMPILE(, [return 0;], [], [CFLAGS=$OLD_CFLAGS])
 done
 
 AC_CANONICAL_SYSTEM