Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -20,14 +20,11 @@
 CPP="$OBJCPP"
 CPPFLAGS="$CPPFLAGS $OBJCPPFLAGS"
 OBJCFLAGS="$OBJCFLAGS -Wall -fexceptions -fobjc-exceptions"
 OBJCFLAGS="$OBJCFLAGS -fconstant-string-class=OFConstantString"
 
-AX_CHECK_COMPILER_FLAGS(-std=gnu99, [
-	OBJCFLAGS="$OBJCFLAGS -std=gnu99"
-	AC_SUBST(GNU99, "-std=gnu99")
-])
+AX_CHECK_COMPILER_FLAGS(-std=gnu99, [OBJCFLAGS="$OBJCFLAGS -std=gnu99"])
 AX_CHECK_COMPILER_FLAGS([-fgnu89-inline -Werror],
 	[OBJCFLAGS="$OBJCFLAGS -fgnu89-inline"])
 AX_CHECK_COMPILER_FLAGS(-pipe, [OBJCFLAGS="$OBJCFLAGS -pipe"])
 AX_CHECK_COMPILER_FLAGS(-fno-common, [OBJCFLAGS="$OBJCFLAGS -fno-common"])
 AX_CHECK_COMPILER_FLAGS(-fno-constant-cfstrings, [

Index: src/OFString.h
==================================================================
--- src/OFString.h
+++ src/OFString.h
@@ -18,10 +18,12 @@
 #include <stdarg.h>
 #include <inttypes.h>
 
 #import "OFObject.h"
 #import "OFSerialization.h"
+
+#import "macros.h"
 
 @class OFConstantString;
 
 typedef uint32_t of_unichar_t;
 

Index: src/macros.h
==================================================================
--- src/macros.h
+++ src/macros.h
@@ -39,10 +39,16 @@
 # define OF_INLINE inline
 # define OF_LIKELY(cond) cond
 # define OF_UNLIKELY(cond) cond
 # define OF_CONST_FUNC
 #endif
+
+#if defined(__GNUC__)
+# define restrict __restrict__
+#elif __STDC_VERSION__ < 199901L
+# define restrict
+#endif
 
 /* Required to build universal binaries on OS X */
 #if __BIG_ENDIAN__ || __LITTLE_ENDIAN__
 # if __BIG_ENDIAN__ && __LITTLE_ENDIAN__
 #  error __BIG_ENDIAN__ and __LITTLE_ENDIAN__ defined!

Index: utils/objfw-config.in
==================================================================
--- utils/objfw-config.in
+++ utils/objfw-config.in
@@ -20,11 +20,11 @@
 libdir="@libdir@"
 CFLAGS=""
 CPPFLAGS="-I@includedir@"
 CXXFLAGS=""
 OBJC="@OBJC@"
-OBJCFLAGS="@GNU99@ @GNU_RUNTIME@ -fexceptions -fobjc-exceptions"
+OBJCFLAGS="@GNU_RUNTIME@ -fexceptions -fobjc-exceptions"
 OBJCFLAGS="$OBJCFLAGS -fconstant-string-class=OFConstantString"
 OBJCFLAGS="$OBJCFLAGS @NO_CONST_CFSTRINGS@ @BLOCKS_FLAGS@ @NO_WARN_UNUSED@"
 LIB_CFLAGS="@LIB_CFLAGS@"
 LIB_LDFLAGS="@LIB_LDFLAGS@"
 LIB_PREFIX="@LIB_PREFIX@"