Index: configure.ac
==================================================================
--- configure.ac
+++ configure.ac
@@ -170,10 +170,14 @@
 
 	AC_CHECK_FUNC(objc_sync_enter,, [
 		AC_SUBST(OBJC_SYNC_M, "objc_sync.m")
 		AC_DEFINE(NEED_OBJC_SYNC_INIT, 1,
 			[Whether objc_sync_init needs to be called])])
+
+	AC_CHECK_HEADER(libkern/OSAtomic.h, [
+		AC_DEFINE(OF_HAVE_LIBKERN_OSATOMIC_H, 1,
+			[Whether we have libkern/OSAtomic.h])])
 fi
 
 AC_CHECK_LIB(socket, socket, LIBS="$LIBS -lsocket")
 AC_CHECK_LIB(ws2_32, main, LIBS="$LIBS -lws2_32")
 

Index: src/Makefile
==================================================================
--- src/Makefile
+++ src/Makefile
@@ -33,10 +33,11 @@
 INCLUDES := ${SRCS:.m=.h}	\
 	    OFFastEnumeration.h	\
 	    OFMacros.h		\
 	    ObjFW.h		\
 	    asprintf.h		\
+	    atomic.h		\
 	    objfw-defs.h	\
 	    ${THREADING_H}
 
 SRCS += ${AS_PRINTF_M} 		\
 	iso_8859_15.m		\

Index: src/OFObject.m
==================================================================
--- src/OFObject.m
+++ src/OFObject.m
@@ -28,10 +28,12 @@
 #endif
 #ifdef OF_GNU_RUNTIME
 # import <objc/sarray.h>
 #endif
 
+#import "atomic.h"
+
 struct pre_ivar {
 	void   **memchunks;
 	size_t memchunks_size;
 	size_t retain_count;
 };
@@ -471,11 +473,11 @@
 						      pointer: ptr];
 }
 
 - retain
 {
-	PRE_IVAR->retain_count++;
+	of_atomic_inc32(&PRE_IVAR->retain_count);
 
 	return self;
 }
 
 - (size_t)retainCount
@@ -483,11 +485,11 @@
 	return PRE_IVAR->retain_count;
 }
 
 - (void)release
 {
-	if (!--PRE_IVAR->retain_count)
+	if (!of_atomic_dec32(&PRE_IVAR->retain_count))
 		[self dealloc];
 }
 
 - autorelease
 {

ADDED   src/atomic.h
Index: src/atomic.h
==================================================================
--- src/atomic.h
+++ src/atomic.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2008 - 2009
+ *   Jonathan Schleifer <js@webkeks.org>
+ *
+ * All rights reserved.
+ *
+ * This file is part of ObjFW. It may be distributed under the terms of the
+ * Q Public License 1.0, which can be found in the file LICENSE included in
+ * the packaging of this file.
+ */
+
+#import "objfw-defs.h"
+
+#if !defined(OF_THREADS)
+# define of_atomic_inc32(p) ++(*p)
+# define of_atomic_dec32(p) --(*p)
+#elif __GNUC_MINOR__ >= 1
+# define of_atomic_inc32(p) __sync_add_and_fetch(p, 1)
+# define of_atomic_dec32(p) __sync_sub_and_fetch(p, 1)
+#elif OF_HAVE_LIBKERN_OSATOMIC_H
+# include <libkern/OSAtomic.h>
+# define of_atomic_inc32(p) OSAtomicIncrement32Barrier((int32_t*)(p))
+# define of_atomic_dec32(p) OSAtomicDecrement32Barrier((int32_t*)(p))
+#else
+# error No atomic operations available!
+#endif

Index: src/objfw-defs.h.in
==================================================================
--- src/objfw-defs.h.in
+++ src/objfw-defs.h.in
@@ -1,7 +1,8 @@
 #undef OF_APPLE_RUNTIME
 #undef OF_BIG_ENDIAN
 #undef OF_GNU_RUNTIME
 #undef OF_HAVE_ASPRINTF
+#undef OF_HAVE_LIBKERN_OSATOMIC_H
 #undef OF_PLUGINS
 #undef OF_THREADS
 #undef SIZE_MAX