Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -2008,10 +2008,12 @@
 		AS_HELP_STRING([--disable-werror], [do not build with -Werror]))
 	AS_IF([test x"$enable_werror" != x"no"], [
 		OBJCFLAGS="$OBJCFLAGS -Werror"
 	])
 
+	old_OBJCFLAGS="$OBJCFLAGS"
+	OBJCFLAGS="$OBJCFLAGS -Werror"
 	AC_MSG_CHECKING(whether we need -Wno-strict-aliasing due to GCC bugs)
 	AC_COMPILE_IFELSE([
 		AC_LANG_PROGRAM([
 			#ifdef __has_attribute
 			# if __has_attribute(objc_root_class)
@@ -2031,15 +2033,18 @@
 			Foo *test = (Foo *)&object;
 			(void)test; /* Get rid of unused variable warning */
 		])
 	], [
 		AC_MSG_RESULT(no)
+		OBJCFLAGS="$old_OBJCFLAGS"
 	], [
 		AC_MSG_RESULT(yes)
-		OBJCFLAGS="$OBJCFLAGS -Wno-strict-aliasing"
+		OBJCFLAGS="$old_OBJCFLAGS -Wno-strict-aliasing"
 	])
 
+	old_OBJCFLAGS="$OBJCFLAGS"
+	OBJCFLAGS="$OBJCFLAGS -Werror"
 	AC_MSG_CHECKING(
 	    whether we need -Wno-unused-property-ivar due to Clang bugs)
 	AC_COMPILE_IFELSE([
 		AC_LANG_SOURCE([
 			#ifdef __has_attribute
@@ -2067,17 +2072,18 @@
 			}
 			@end
 		])
 	], [
 		AC_MSG_RESULT(no)
+		OBJCFLAGS="$old_OBJCFLAGS"
 	], [
 		AC_MSG_RESULT(yes)
-		OBJCFLAGS="$OBJCFLAGS -Wno-unused-property-ivar"
+		OBJCFLAGS="$old_OBJCFLAGS -Wno-unused-property-ivar"
 	])
 
 	old_OBJCFLAGS="$OBJCFLAGS"
-	OBJCFLAGS="$OBJCFLAGS -Wcast-align"
+	OBJCFLAGS="$OBJCFLAGS -Wcast-align -Werror"
 	AC_MSG_CHECKING(whether -Wcast-align is buggy)
 	AC_COMPILE_IFELSE([
 		AC_LANG_SOURCE([
 			#ifdef __has_attribute
 			# if __has_attribute(objc_root_class)
@@ -2098,17 +2104,18 @@
 			}
 			@end
 		])
 	], [
 		AC_MSG_RESULT(no)
+		OBJCFLAGS="$old_OBJCFLAGS -Wcast-align"
 	], [
 		AC_MSG_RESULT(yes)
 		OBJCFLAGS="$old_OBJCFLAGS"
 	])
 
 	old_OBJCFLAGS="$OBJCFLAGS"
-	OBJCFLAGS="$OBJCFLAGS -Wunreachable-code"
+	OBJCFLAGS="$OBJCFLAGS -Wunreachable-code -Werror"
 	AC_MSG_CHECKING(whether -Wunreachable-code can be used)
 	AC_COMPILE_IFELSE([
 		AC_LANG_SOURCE([[
 			#include <stdlib.h>
 
@@ -2174,17 +2181,18 @@
 			}
 			@end
 		]])
 	], [
 		AC_MSG_RESULT(yes)
+		OBJCFLAGS="$old_OBJCFLAGS -Wunreachable-code"
 	], [
 		AC_MSG_RESULT(no)
 		OBJCFLAGS="$old_OBJCFLAGS"
 	])
 
 	old_OBJCFLAGS="$OBJCFLAGS"
-	OBJCFLAGS="$OBJCFLAGS -Wdocumentation"
+	OBJCFLAGS="$OBJCFLAGS -Wdocumentation -Werror"
 	AC_MSG_CHECKING(whether -Wdocumentation works correctly)
 	AC_COMPILE_IFELSE([
 		AC_LANG_SOURCE([
 			/**
 			 * @class Test conftest.m conftest.m
@@ -2202,18 +2210,19 @@
 			 */
 			typedef struct {} Foo;
 		])
 	], [
 		AC_MSG_RESULT(yes)
+		OBJCFLAGS="$old_OBJCFLAGS -Wdocumentation"
 	], [
 		AC_MSG_RESULT(no)
 		OBJCFLAGS="$old_OBJCFLAGS"
 	])
 
 	AS_IF([test x"$check_pedantic" = x"yes"], [
 		old_OBJCFLAGS="$OBJCFLAGS"
-		OBJCFLAGS="$OBJCFLAGS -pedantic"
+		OBJCFLAGS="$OBJCFLAGS -pedantic -Werror"
 		AC_MSG_CHECKING(whether -pedantic is buggy)
 		AC_COMPILE_IFELSE([
 			AC_LANG_SOURCE([
 				#include <stdlib.h>
 
@@ -2245,31 +2254,37 @@
 				}
 				@end
 			])
 		], [
 			AC_MSG_RESULT(no)
+			OBJCFLAGS="$old_OBJCFLAGS -pedantic"
 		], [
 			AC_MSG_RESULT(yes)
 			OBJCFLAGS="$old_OBJCFLAGS"
 		])
 	])
 
+	old_OBJCFLAGS="$OBJCFLAGS"
+	OBJCFLAGS="$OBJCFLAGS -Werror"
 	AC_MSG_CHECKING(whether we need -Wno-strict-prototypes)
 	AC_COMPILE_IFELSE([
 		AC_LANG_PROGRAM([
 			#include <signal.h>
 		], [
 			signal(SIGINT, SIG_DFL);
 		])
 	], [
 		AC_MSG_RESULT(no)
+		OBJCFLAGS="$old_OBJCFLAGS"
 	], [
 		AC_MSG_RESULT(yes)
-		OBJCFLAGS="$OBJCFLAGS -Wno-strict-prototypes"
+		OBJCFLAGS="$old_OBJCFLAGS -Wno-strict-prototypes"
 	])
 
 	AS_IF([test x"$ac_cv_header_complex_h" = x"yes"], [
+		old_OBJCFLAGS="$OBJCFLAGS"
+		OBJCFLAGS="$OBJCFLAGS -Werror"
 		AC_MSG_CHECKING(whether we need -Wno-gnu-imaginary-constant)
 		AC_COMPILE_IFELSE([
 			AC_LANG_PROGRAM([
 				#include <complex.h>
 			], [
@@ -2276,13 +2291,14 @@
 				complex float f = 0.5 + 0.5 * I;
 				(void)f;
 			])
 		], [
 			AC_MSG_RESULT(no)
+			OBJCFLAGS="$old_OBJCFLAGS"
 		], [
 			AC_MSG_RESULT(yes)
-			OBJCFLAGS="$OBJCFLAGS -Wno-gnu-imaginary-constant"
+			OBJCFLAGS="$old_OBJCFLAGS -Wno-gnu-imaginary-constant"
 		])
 	])
 ])
 
 AS_IF([test x"$cross_compiling" = x"yes"], [