Index: src/OFApplication.h
==================================================================
--- src/OFApplication.h
+++ src/OFApplication.h
@@ -162,18 +162,18 @@
 + (OFDictionary*)environment;
 
 /*!
  * @brief Terminates the application.
  */
-+ (void)terminate;
++ (void)terminate OF_NO_RETURN;
 
 /*!
  * @brief Terminates the application with the specified status.
  *
  * @param status The status with which the application will terminate
  */
-+ (void)terminateWithStatus: (int)status;
++ (void)terminateWithStatus: (int)status OF_NO_RETURN;
 
 /*!
  * @brief Gets args and argv.
  *
  * @param argc A pointer where a pointer to argc should be stored

Index: src/OFDeflateStream.m
==================================================================
--- src/OFDeflateStream.m
+++ src/OFDeflateStream.m
@@ -743,14 +743,13 @@
 
 		break;
 #undef CTX
 	}
 
-	/* Get rid of a warning, never reached anyway */
-	OF_ENSURE(0);
+	OF_UNREACHABLE
 }
 
 - (bool)lowlevelIsAtEndOfStream
 {
 	return _atEndOfStream;
 }
 @end

Index: src/OFMutableString_UTF8.m
==================================================================
--- src/OFMutableString_UTF8.m
+++ src/OFMutableString_UTF8.m
@@ -265,12 +265,11 @@
 			    resizeMemory: _s->cString
 				    size: _s->cStringLength + 1];
 		} @catch (OFOutOfMemoryException *e) {
 			/* We don't really care, as we only made it smaller */
 		}
-	} else
-		assert(0);
+	}
 }
 
 - (void)appendUTF8String: (const char*)UTF8String
 {
 	size_t UTF8StringLength = strlen(UTF8String);

Index: src/OFObject.h
==================================================================
--- src/OFObject.h
+++ src/OFObject.h
@@ -91,12 +91,14 @@
 # endif
 #endif
 
 #if defined(__clang__) || __GCC_VERSION__ >= 406
 # define OF_SENTINEL __attribute__((sentinel))
+# define OF_NO_RETURN __attribute__((noreturn))
 #else
 # define OF_SENTINEL
+# define OF_NO_RETURN
 #endif
 
 #if __has_attribute(objc_requires_super)
 # define OF_REQUIRES_SUPER __attribute__((objc_requires_super))
 #else
@@ -944,11 +946,11 @@
  * @warning If you override this method, you must make sure that it never
  *	    returns.
  *
  * @param selector The selector not understood by the receiver
  */
-- (void)doesNotRecognizeSelector: (SEL)selector;
+- (void)doesNotRecognizeSelector: (SEL)selector OF_NO_RETURN;
 @end
 
 /*!
  * @protocol OFCopying OFObject.h ObjFW/OFObject.h
  *

Index: src/OFThread.h
==================================================================
--- src/OFThread.h
+++ src/OFThread.h
@@ -143,18 +143,18 @@
 
 #ifdef OF_HAVE_THREADS
 /*!
  * @brief Terminates the current thread, letting it return nil.
  */
-+ (void)terminate;
++ (void)terminate OF_NO_RETURN;
 
 /*!
  * @brief Terminates the current thread, letting it return the specified object.
  *
  * @param object The object which the terminated thread will return
  */
-+ (void)terminateWithObject: (id)object;
++ (void)terminateWithObject: (id)object OF_NO_RETURN;
 
 # ifdef OF_HAVE_BLOCKS
 /*!
  * @brief Initializes an already allocated thread with the specified block.
  *

Index: src/OFThread.m
==================================================================
--- src/OFThread.m
+++ src/OFThread.m
@@ -236,10 +236,17 @@
 
 #ifdef OF_HAVE_THREADS
 + (void)terminate
 {
 	[self terminateWithObject: nil];
+
+	/*
+	 * For some reason, Clang thinks terminateWithObject: can return - even
+	 * though it is declared noreturn - and warns that terminate returns
+	 * while being declared noreturn.
+	 */
+	OF_UNREACHABLE
 }
 
 + (void)terminateWithObject: (id)object
 {
 	OFThread *thread = of_tlskey_get(threadSelfKey);

Index: src/macros.h
==================================================================
--- src/macros.h
+++ src/macros.h
@@ -145,14 +145,20 @@
 #define OF_IVAR_OFFSET(ivar) ((intptr_t)&ivar - (intptr_t)self)
 #define OF_GETTER(ivar, atomic) \
 	return objc_getProperty(self, _cmd, OF_IVAR_OFFSET(ivar), atomic);
 #define OF_SETTER(ivar, value, atomic, copy) \
 	objc_setProperty(self, _cmd, OF_IVAR_OFFSET(ivar), value, atomic, copy);
+
+#if defined(__clang__) || __GCC_VERSION__ >= 405
+# define OF_UNREACHABLE __builtin_unreachable();
+#else
+# define OF_UNREACHABLE abort();
+#endif
 
 #define OF_UNRECOGNIZED_SELECTOR		\
 	[self doesNotRecognizeSelector: _cmd];	\
-	abort();
+	OF_UNREACHABLE
 #define OF_INVALID_INIT_METHOD				\
 	@try {						\
 		[self doesNotRecognizeSelector: _cmd];	\
 	} @catch (id e) {				\
 		[self release];				\

Index: src/threading.h
==================================================================
--- src/threading.h
+++ src/threading.h
@@ -141,11 +141,11 @@
 #else
 # error of_thread_detach not implemented!
 #endif
 }
 
-static OF_INLINE void
+static OF_INLINE void OF_NO_RETURN
 of_thread_exit(void)
 {
 #if defined(OF_HAVE_PTHREADS)
 	pthread_exit(NULL);
 #elif defined(_WIN32)