Don't do hidden-class transforms for classes, just dangle the look-aside data off the class structure.

Individually lock classes so that +initialize can be sent concurrently to two different classes in two different threads.

associate.m

@@ -181,12 +181,12 @@ static Class allocateHiddenClass(Class superclass)
 	// Set the superclass pointer to the name.  The runtime will fix this when
 	// the class links are resolved.
 	newClass->name = superclass->name;
-	newClass->info = objc_class_flag_resolved | objc_class_flag_initialized |
+	newClass->info = objc_class_flag_resolved | 
 		objc_class_flag_class | objc_class_flag_user_created |
 		objc_class_flag_new_abi | objc_class_flag_hidden_class |
 		objc_class_flag_assoc_class;
 	newClass->super_class = superclass;
-	newClass->dtable = objc_copy_dtable_for_class(superclass->dtable, newClass);
+	newClass->dtable = uninstalled_dtable;
 	newClass->instance_size = superclass->instance_size;
 	if (objc_test_class_flag(superclass, objc_class_flag_meta))
 	{
@@ -235,13 +235,25 @@ static void deallocHiddenClass(id obj, SEL _cmd)
 	free(hiddenClass);
 }
 
-void objc_setAssociatedObject(id object,
-                              void *key,
-                              id value,
-                              objc_AssociationPolicy policy)
+static struct reference_list* referenceListForObject(id object, BOOL create)
 {
+	if (class_isMetaClass(object->isa))
+	{
+		Class cls = (Class)object;
+		if ((NULL == cls->extra_data) && create)
+		{
+			int *lock = lock_for_pointer(cls);
+			lock_spinlock(lock);
+			if (NULL == cls->extra_data)
+			{
+				cls->extra_data = calloc(1, sizeof(struct reference_list));
+			}
+			unlock_spinlock(lock);
+		}
+		return cls->extra_data;
+	}
 	Class hiddenClass = findHiddenClass(object);
-	if (NULL == hiddenClass)
+	if ((NULL == hiddenClass) && create)
 	{
 		int *lock = lock_for_pointer(object);
 		lock_spinlock(lock);
@@ -252,15 +264,22 @@ void objc_setAssociatedObject(id object,
 		}
 		unlock_spinlock(lock);
 	}
-	struct reference_list *list = object_getIndexedIvars(hiddenClass);
+	return hiddenClass ? object_getIndexedIvars(hiddenClass) : NULL;
+}
+
+void objc_setAssociatedObject(id object,
+                              void *key,
+                              id value,
+                              objc_AssociationPolicy policy)
+{
+	struct reference_list *list = referenceListForObject(object, YES);
 	setReference(list, key, value, policy);
 }
 
 id objc_getAssociatedObject(id object, void *key)
 {
-	Class hiddenClass = findHiddenClass(object);
-	if (NULL == hiddenClass) { return nil; }
-	struct reference_list *list = object_getIndexedIvars(hiddenClass);
+	struct reference_list *list = referenceListForObject(object, NO);
+	if (NULL == list) { return nil; }
 	struct reference *r = findReference(list, key);
 	return r ? r->object : nil;
 }
@@ -268,8 +287,5 @@ id objc_getAssociatedObject(id object, void *key)
 
 void objc_removeAssociatedObjects(id object)
 {
-	Class hiddenClass = findHiddenClass(object);
-	if (NULL == hiddenClass) { return; }
-	struct reference_list *list = object_getIndexedIvars(hiddenClass);
-	cleanupReferenceList(list);
+	cleanupReferenceList(referenceListForObject(object, NO));
 }

class.h

@@ -76,7 +76,7 @@ struct objc_class
 	/**
 	 * Linked list of extra data attached to this class.
 	 */
-	struct class_annotation  *extra_data;
+	struct reference_list      *extra_data;
 	/**
 	* New ABI.  The following fields are only available with classes compiled to
 	* support the new ABI.  You may test whether any given class supports this

dtable.c

@@ -28,7 +28,6 @@ static void collectMethodsForMethodListToSparseArray(
 	}
 	for (unsigned i=0 ; i<list->count ; i++)
 	{
-		//fprintf(stderr, "Adding method %s (%d)\n", sel_getName(list->methods[i].selector), PTR_TO_IDX(list->methods[i].selector->name));
 		SparseArrayInsert(sarray, list->methods[i].selector->index,
 				(void*)&list->methods[i]);
 	}
@@ -74,7 +73,7 @@ PRIVATE void update_dispatch_table_for_class(Class cls)
 	}
 }
 
-static dtable_t create_dtable_for_class(Class class)
+static SparseArray *create_dtable_for_class(Class class, dtable_t root_dtable)
 {
 	// Don't create a dtable for a class that already has one
 	if (classHasDtable(class)) { return dtable_for_class(class); }
@@ -85,8 +84,6 @@ static dtable_t create_dtable_for_class(Class class)
 	// waiting on the lock.
 	if (classHasDtable(class)) { return dtable_for_class(class); }
 
-	Class super = class_getSuperclass(class);
-
 	/* Allocate dtable if necessary */
 	dtable_t dtable = calloc(1, sizeof(struct objc_dtable));
 	dtable->cls = class;
@@ -179,7 +176,6 @@ static void insert_slot(dtable_t dtable, struct objc_slot *slot, uint32_t idx)
 
 static void update_dtable(dtable_t dtable)
 {
-	//fprintf(stderr, "Updating dtable for %s! %d\n", dtable->cls->name, dtable_depth);
 	Class cls = dtable->cls;
 
 	if (NULL == cls->methods) { return; }
@@ -253,7 +249,6 @@ PRIVATE struct objc_slot* objc_dtable_lookup(dtable_t dtable, uint32_t uid)
 	{
 		update_dtable(dtable);
 	}
-	//fprintf(stderr, "Using slow path: %d entries in table for %s\n", dtable->slot_count, dtable->cls->name);
 	struct slots_list *s = find_slot(uid, dtable->slots, dtable->slot_count);
 	if (NULL != s)
 	{
@@ -302,7 +297,6 @@ static BOOL installMethodInDtable(Class class,
 	struct objc_slot *slot = SparseArrayLookup(dtable, sel_id);
 	if (NULL != slot)
 	{
-		//fprintf(stderr, "Slot already exists...\n");
 		// If this method is the one already installed, pretend to install it again.
 		if (slot->method == method->imp) { return NO; }
 
@@ -314,7 +308,6 @@ static BOOL installMethodInDtable(Class class,
 			// Don't replace methods if we're not meant to (if they're from
 			// later in a method list, for example)
 			if (!replaceExisting) { return NO; }
-			//fprintf(stderr, "Replacing method %p %s in %s with %p\n", slot->method, sel_getName(method->selector), class->name, method->imp);
 			slot->method = method->imp;
 			return YES;
 		}
@@ -328,13 +321,11 @@ static BOOL installMethodInDtable(Class class,
 		{
 			if (installedFor == owner)
 			{
-		//fprintf(stderr, "Not installing %s from %s in %s - already overridden from %s\n", sel_getName(method->selector), owner->name, class->name, slot->owner->name);
 				return NO;
 			}
 		}
 	}
 	struct objc_slot *oldSlot = slot;
-	//fprintf(stderr, "Installing method %p (%d) %s in %s (previous slot owned by %s)\n", method->imp, sel_id, sel_getName(method->selector), class->name, slot? oldSlot->owner->name: "(no one)");
 	slot = new_slot_for_method_in_class((void*)method, owner);
 	SparseArrayInsert(dtable, sel_id, slot);
 	// In TDD mode, we also register the first typed method that we
@@ -345,7 +336,6 @@ static BOOL installMethodInDtable(Class class,
 	// Invalidate the old slot, if there is one.
 	if (NULL != oldSlot)
 	{
-		//fprintf(stderr, "Overriding method %p %s from %s in %s with %x\n", slot->method, sel_getName(method->selector), oldSlot->owner->name, class->name, method->imp);
 		oldSlot->version++;
 	}
 	return YES;
@@ -398,11 +388,9 @@ PRIVATE void objc_update_dtable_for_class(Class cls)
 {
 	// Only update real dtables
 	if (!classHasDtable(cls)) { return; }
-	//fprintf(stderr, "Updating dtable for %s\n", cls->name);
 
 	LOCK_RUNTIME_FOR_SCOPE();
 
-	//fprintf(stderr, "Adding methods to %s\n", cls->name);
 	SparseArray *methods = SparseArrayNewWithDepth(dtable_depth);
 	collectMethodsForMethodListToSparseArray((void*)cls->methods, methods);
 	installMethodsInClass(cls, cls, methods, YES);
@@ -422,7 +410,7 @@ PRIVATE void update_dispatch_table_for_class(Class cls)
 	objc_update_dtable_for_class(cls);
 }
 
-static SparseArray *create_dtable_for_class(Class class)
+static SparseArray *create_dtable_for_class(Class class, dtable_t root_dtable)
 {
 	// Don't create a dtable for a class that already has one
 	if (classHasDtable(class)) { return dtable_for_class(class); }
@@ -446,9 +434,16 @@ static SparseArray *create_dtable_for_class(Class class)
 		dtable_t super_dtable = dtable_for_class(super);
 		if (super_dtable == uninstalled_dtable)
 		{
-			super_dtable = create_dtable_for_class(super);
+			if (super->isa == class)
+			{
+				super_dtable = root_dtable;
+			}
+			else
+			{
+				abort();
+			}
 		}
-		dtable = SparseArrayCopy(dtable_for_class(super));
+		dtable = SparseArrayCopy(super_dtable);
 	}
 
 	// When constructing the initial dtable for a class, we iterate along the
@@ -508,6 +503,19 @@ PRIVATE dtable_t objc_copy_dtable_for_class(dtable_t old, Class cls)
 
 void objc_resolve_class(Class);
 
+int objc_sync_enter(id);
+int objc_sync_exit(id);
+
+__attribute__((unused)) static void objc_release_object_lock(id *x)
+{
+	objc_sync_exit(*x);
+}
+#define LOCK_OBJECT_FOR_SCOPE(obj) \
+	__attribute__((cleanup(objc_release_object_lock)))\
+	__attribute__((unused)) id lock_object_pointer = obj;\
+	objc_sync_enter(obj);
+
+
 /**
  * Send a +initialize message to the receiver, if required.  
  */
@@ -532,7 +540,6 @@ PRIVATE void objc_send_initialize(id object)
 	// NOTE: Ideally, we would actually lock on the class object using
 	// objc_sync_enter().  This should be fixed once sync.m contains a (fast)
 	// special case for classes.
-	LOCK_FOR_SCOPE(&initialize_lock);
 
 	// Make sure that the class is resolved.
 	objc_resolve_class(class);
@@ -543,19 +550,48 @@ PRIVATE void objc_send_initialize(id object)
 		objc_send_initialize((id)class->super_class);
 	}
 
+	LOCK(&initialize_lock);
+
 	// Superclass +initialize might possibly send a message to this class, in
 	// which case this method would be called again.  See NSObject and
 	// NSAutoreleasePool +initialize interaction in GNUstep.
-	if (objc_test_class_flag(class, objc_class_flag_initialized)) { return; }
+	if (objc_test_class_flag(class, objc_class_flag_initialized))
+	{
+		UNLOCK(&initialize_lock);
+		return;
+	}
 
 	// Set the initialized flag on both this class and its metaclass, to make
 	// sure that +initialize is only ever sent once.
 	objc_set_class_flag(class, objc_class_flag_initialized);
 	objc_set_class_flag(meta, objc_class_flag_initialized);
 
+	dtable_t class_dtable = create_dtable_for_class(class, uninstalled_dtable);
+	dtable_t dtable = create_dtable_for_class(meta, class_dtable);
+
+	static SEL initializeSel = 0;
+	if (0 == initializeSel)
+	{
+		initializeSel = sel_registerName("initialize");
+	}
+
+	struct objc_slot *initializeSlot = 
+		objc_dtable_lookup(dtable, initializeSel->index);
+
+	// If there's no initialize method, then don't bother installing and
+	// removing the initialize dtable, just install both dtables correctly now
+	if (0 == initializeSlot || initializeSlot->owner != meta)
+	{
+		meta->dtable = dtable;
+		class->dtable = class_dtable;
+		UNLOCK(&initialize_lock);
+		return;
+	}
+
+	LOCK_OBJECT_FOR_SCOPE((id)class);
+
 
 	// Create a temporary dtable, to be installed later.
-	dtable_t class_dtable = create_dtable_for_class(class);
 	InitializingDtable buffer = { class, class_dtable, temporary_dtables };
 	temporary_dtables = &buffer;
 
@@ -563,9 +599,9 @@ PRIVATE void objc_send_initialize(id object)
 	// a message to this class in future, the lookup function will check this
 	// buffer if the receiver's dtable is not installed, and block if
 	// attempting to send a message to this class.
-	dtable_t dtable = create_dtable_for_class(meta);
 	InitializingDtable meta_buffer = { meta, dtable, temporary_dtables };
 	temporary_dtables = &meta_buffer;
+	UNLOCK(&initialize_lock);
 
 	// Store the buffer in the temporary dtables list.  Note that it is safe to
 	// insert it into a global list, even though it's a temporary variable,
@@ -573,44 +609,15 @@ PRIVATE void objc_send_initialize(id object)
 	//
 	// FIXME: This will actually break if +initialize throws an exception...
 
-	static SEL initializeSel = 0;
-	if (0 == initializeSel)
-	{
-		initializeSel = sel_registerName("initialize");
-	}
-	struct objc_slot *initializeSlot = 
-		objc_dtable_lookup(dtable, initializeSel->index);
-
-	if (0 != initializeSlot)
-	{
-		if (Nil != class->super_class)
-		{
-			// The dtable to use for sending messages to the superclass.  This
-			// is the superclass's metaclass' dtable.
-			dtable_t super_dtable = dtable_for_class(class->super_class->isa);
-			struct objc_slot *superSlot = objc_dtable_lookup(super_dtable,
-					initializeSel->index);
-			// Check that this IMP comes from the class, not from its
-			// superclass.  We still have to use dtable_for_class() here
-			// because our +initialize call might be in response to a message
-			// sent from a subclass (e.g. NSObject +initialize sending a
-			// message to NSAutoreleasePool: NSObject's dtable won't have been
-			// installed at this point.
-			if (0 == superSlot || superSlot->method != initializeSlot->method)
-			{
-				initializeSlot->method((id)class, initializeSel);
-			}
-		}
-		else
-		{
 	initializeSlot->method((id)class, initializeSel);
-		}
-	}
 
-	// Install the real dtable for both the class and the metaclass.
+	// Install the real dtable for both the class and the metaclass.  We can do
+	// this without the lock, because now both ways of accessing the dtable are
+	// safe.  We only need the lock when we remove the cached version.
 	meta->dtable = dtable;
 	class->dtable = class_dtable;
 
+	LOCK(&initialize_lock);
 	// Remove the look-aside buffer entry.
 	if (temporary_dtables == &meta_buffer)
 	{
@@ -625,4 +632,5 @@ PRIVATE void objc_send_initialize(id object)
 		}
 		prev->next = buffer.next;
 	}
+	UNLOCK(&initialize_lock);
 }

dtable.h

@@ -4,6 +4,7 @@
 #include "objc/slot.h"
 #include "visibility.h"
 #include <stdint.h>
+#include <stdio.h>
 
 #ifdef __OBJC_LOW_MEMORY__
 typedef struct objc_dtable* dtable_t;
@@ -56,6 +57,7 @@ static inline dtable_t dtable_for_class(Class cls)
 	{
 		return cls->dtable;
 	}
+
 	LOCK_FOR_SCOPE(&initialize_lock);
 	if (classHasInstalledDtable(cls))
 	{

sendmsg2.c

@@ -116,7 +116,6 @@ Slot_t (*objc_plane_lookup)(id *receiver, SEL op, id sender) =
  */
 Slot_t objc_msg_lookup_sender(id *receiver, SEL selector, id sender)
 {
-	//fprintf(stderr, "Looking up slot %s\n", sel_get_name(selector));
 	// Returning a nil slot allows the caller to cache the lookup for nil too,
 	// although this is not particularly useful because the nil method can be
 	// inlined trivially.
@@ -140,7 +139,6 @@ Slot_t objc_msg_lookup_sender(id *receiver, SEL selector, id sender)
 	void *receiverPlaneID = *((void**)receiver - 1);
 	if (senderPlaneID == receiverPlaneID)
 	{
-		//fprintf(stderr, "Intraplane message\n");
 		return objc_msg_lookup_internal(receiver, selector, sender);
 	}
 	return objc_plane_lookup(receiver, selector, sender);
@@ -260,7 +258,6 @@ Slot_t objc_get_slot(Class cls, SEL selector)
 		/* Install the dtable if it hasn't already been initialized. */
 		if (dtable == uninstalled_dtable)
 		{
-			//objc_send_initialize((id)cls);
 			dtable = dtable_for_class(cls);
 			result = objc_dtable_lookup(dtable, selector->index);
 		}
@@ -270,6 +267,7 @@ Slot_t objc_get_slot(Class cls, SEL selector)
 			// weren't looking
 			result = objc_dtable_lookup(dtable, selector->index);
 		}
+		Class class = cls;
 		if (NULL == result)
 		{
 			if (!isSelRegistered(selector))