From d5636dc17a6a5a11e2d98316c8e5951c804475c2 Mon Sep 17 00:00:00 2001
From: Thomas Goyne <plorkyeran@aegisub.org>
Date: Thu, 2 Jan 2014 15:17:49 -0800
Subject: [PATCH] Use -Werror for compiler flag support checks so that they
 actually work

---
 aegisub/m4macros/ac_flag.m4 | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/aegisub/m4macros/ac_flag.m4 b/aegisub/m4macros/ac_flag.m4
index cf3248a4e..7b22ccad0 100644
--- a/aegisub/m4macros/ac_flag.m4
+++ b/aegisub/m4macros/ac_flag.m4
@@ -1,12 +1,14 @@
 AC_DEFUN([AC_C_FLAG], [{
 	AC_LANG_PUSH(C)
 	ac_c_flag_save="$CFLAGS"
-	CFLAGS="$CFLAGS $1"
+	CFLAGS="$CFLAGS -Werror $1"
 	AC_MSG_CHECKING([[whether $CC supports $1]])
 	AC_COMPILE_IFELSE(
 		[AC_LANG_PROGRAM([[]])],
-		[AC_MSG_RESULT([yes])],
 		[
+			CFLAGS="$ac_c_flag_save $1"
+			AC_MSG_RESULT([yes])
+		], [
 			CFLAGS="$ac_c_flag_save"
 			AC_MSG_RESULT([no])
 			$2
@@ -16,11 +18,14 @@ AC_DEFUN([AC_C_FLAG], [{
 AC_DEFUN([AC_CXX_FLAG], [{
 	AC_LANG_PUSH(C++)
 	ac_cxx_flag_save="$CXXFLAGS"
-	CXXFLAGS="$CXXFLAGS $1"
+	CXXFLAGS="$CXXFLAGS -Werror $1"
 	AC_MSG_CHECKING([[whether $CXX supports $1]])
 	AC_COMPILE_IFELSE(
 		[AC_LANG_PROGRAM([[]])],
-		[AC_MSG_RESULT([yes])],
+		[
+			CXXFLAGS="$ac_cxx_flag_save $1"
+			AC_MSG_RESULT([yes])
+		],
 		[
 			CXXFLAGS="$ac_cxx_flag_save"
 			AC_MSG_RESULT([no])