Garbage collection:

Moved from reference counting over to a mark and sweep method.  Objects
are now required to implement an allRefs method which returns a pointer
to a list of all other referenced objects.  How the list is maintained
is up to each object.  The retain/release mechanism still works; objects
with any references will not be garbage collected, even if the collector
thinks they should be.

include/QF/classes/ArrayList.h

@@ -37,6 +37,7 @@
 classDecl (ArrayList, List,
 	unsigned int realsize;
 	Object **elements;
+	ObjRefs_t allrefs;
 );
 #define ARRAYLIST(o) ((ArrayList *)(o))
 
@@ -45,6 +46,7 @@ classDecl (ArrayListIterator, Iterator,
 	unsigned int pos;
 	unsigned int smods;
 	qboolean alive;
+	ObjRefs_t allrefs;
 );
 #define ARRAYLISTITERATOR(o) ((ArrayListIterator *)(o))
 

include/QF/object.h

@@ -61,6 +61,12 @@
 
 #define instanceOf(obj, cl) (Object_InstaceOf((Object *)obj, cl##_class))
 
+typedef struct ObjRefs_s {
+	struct Object_s **objs;
+	unsigned int count;
+	struct ObjRefs_s *next;
+} ObjRefs_t;
+
 struct Object_s;
 struct Class_s;
 struct List_s;
@@ -70,10 +76,10 @@ typedef void (*ReplyHandler_t) (struct Object_s *retValue);
 typedef struct Object_s {
 	struct Class_s *cl;
 	int refs;
-	qboolean junked;
+	qboolean marked;
 	struct Object_s *next;
 	struct String_s * methodDecl(Object, toString);
-	void methodDecl(Object, message, const char *name, struct List_s *args, struct Object_s *sender, ReplyHandler_t *reply);
+	ObjRefs_t * methodDecl(Object, allRefs);
 	void *data;
 
 } Object;
@@ -99,6 +105,8 @@ void Object_Delete (Object *obj);
 Object *Object_Retain (Object *obj);
 Object *Object_Release (Object *obj);
 qboolean Object_InstanceOf (Object *obj, Class *cl);
+void Object_AddToRoot (Object *obj);
+void Object_RemoveFromRoot (Object *obj);
 void Object_Init (void);
 void Object_Garbage_Collect (void);
 

include/garbage.h

@@ -32,8 +32,9 @@
 #ifndef __garbage_h
 #define __garbage_h
 
-void Garbage_Junk_Object (Object *o);
-unsigned int Garbage_Amount (void);
-void Garbage_Collect (unsigned int amount);
+void Garbage_Do_Mark (Object *root);
+void Garbage_Do_Sweep (Object **allobjs);
+unsigned int Garbage_Pending (void);
+void Garbage_Dispose (unsigned int amount);
 
 #endif

libs/object/ArrayList.c

@@ -46,6 +46,12 @@ static __attribute__ ((unused)) const char rcsid[] =
 
 #include "QF/classes/ArrayList.h"
 
+static ObjRefs_t *
+ArrayListIterator_AllRefs_f (Object *self)
+{
+	return &ARRAYLISTITERATOR(self)->allrefs;
+}
+
 static Object *
 ArrayListIterator_Next_f (Iterator *self)
 {
@@ -75,9 +81,13 @@ static Object *
 ArrayListIterator_Init_f (Object *self, ArrayList *list)
 {
 	superInit (ArrayListIterator, self);
+	self->allRefs = ArrayListIterator_AllRefs_f;
 	ITERATOR(self)->next = ArrayListIterator_Next_f;
 	ITERATOR(self)->hasNext = ArrayListIterator_HasNext_f;
-	ARRAYLISTITERATOR(self)->list = ARRAYLIST(retain(list));
+	ARRAYLISTITERATOR(self)->list = ARRAYLIST(list);
+	ARRAYLISTITERATOR(self)->allrefs.objs = (Object **)&ARRAYLISTITERATOR(self)->list;
+	ARRAYLISTITERATOR(self)->allrefs.count = 1;
+	ARRAYLISTITERATOR(self)->allrefs.next = NULL;
 	ARRAYLISTITERATOR(self)->smods = LIST(list)->smods;
 	ARRAYLISTITERATOR(self)->pos = 0;
 	ARRAYLISTITERATOR(self)->alive = COLLECTION(list)->count ? true : false;
@@ -87,7 +97,15 @@ ArrayListIterator_Init_f (Object *self, ArrayList *list)
 static void
 ArrayListIterator_Deinit_f (Object *self)
 {
-	release(ARRAYLISTITERATOR(self)->list);
+}
+
+static ObjRefs_t *
+ArrayList_AllRefs_f (Object *self)
+{
+	ARRAYLIST(self)->allrefs.objs = ARRAYLIST(self)->elements;
+	ARRAYLIST(self)->allrefs.count = COLLECTION(self)->count;
+	ARRAYLIST(self)->allrefs.next = NULL;
+	return &ARRAYLIST(self)->allrefs;
 }
 
 static void
@@ -109,13 +127,8 @@ ArrayList_Set_f (List *self, unsigned int index, Object *o)
 		if (!Object_InstanceOf (o, COLLECTION(list)->type))
 			return false;
 		ArrayList_EnsureCapacity (list, index+1);
-		retain(o);
-		if (list->elements[index])
-			release (list->elements[index]);
 		list->elements[index] = o;
 	} else if (index < COLLECTION(list)->count) {
-		if (list->elements[index])
-			release (list->elements[index]);
 		list->elements[index] = NULL;
 	}
 	if (COLLECTION(list)->count < index+1)
@@ -151,7 +164,6 @@ ArrayList_InsertAt_f (List *self, unsigned int index, Object *o)
 		return false;
 	else {
 		ArrayList_MakeRoomAt (list, index);
-		retain(o);
 		list->elements[index] = o;
 		return true;
 	}
@@ -165,8 +177,6 @@ ArrayList_RemoveAt_f (List *self, unsigned int index)
 		return NULL;
 	else {
 		Object *o = list->elements[index];
-		if (o)
-			release(o);
 		COLLECTION(list)->count--;
 		memmove(list->elements+index, list->elements+index+1, sizeof(Object *) * (COLLECTION(list)->count-index));
 		LIST(list)->smods++;
@@ -183,8 +193,6 @@ ArrayList_Add_f (Collection *self, Object *o)
 	else {
 		ArrayList_EnsureCapacity (list, ++COLLECTION(list)->count);
 		list->elements[COLLECTION(list)->count-1] = o;
-		if (o)
-			retain(o);
 		return true;
 	}
 }
@@ -207,16 +215,13 @@ ArrayList_Init_f (Object *self, Class *type, Collection *source)
 	COLLECTION(self)->add = ArrayList_Add_f;
 	COLLECTION(self)->iterator = ArrayList_Iterator_f;
 	superInit(List, self, type, source);
+	self->allRefs = ArrayList_AllRefs_f;
 	return self;
 }
 
 static void
 ArrayList_Deinit_f (Object *self)
 {
-	unsigned int i;
-	for (i = 0; i < COLLECTION(self)->count; i++)
-		if (ARRAYLIST(self)->elements[i])
-			release(ARRAYLIST(self)->elements[i]);
 	free(ARRAYLIST(self)->elements);
 }
 

libs/object/Double.c

@@ -43,7 +43,7 @@ static __attribute__ ((unused)) const char rcsid[] =
 static String *
 Double_ToString_f (Object *self)
 {
-	return new (String, va("%f", DOUBLE(self)->value));
+	return newFloat(String, va("%f", DOUBLE(self)->value));
 }
 
 static int

libs/object/garbage.c

@@ -42,48 +42,61 @@ static __attribute__ ((unused)) const char rcsid[] =
 
 #include "garbage.h"
 
-unsigned int junked = 0;
 Object *junk = NULL;
+unsigned int junked = 0;
 
 void
-Garbage_Junk_Object (Object *o)
+Garbage_Do_Mark (Object *root)
 {
-	Sys_DPrintf ("GC: %s@%p ready for collection.\n", o->cl->name, o);
-	if (!o->junked && !o->refs) {
-		o->next = junk;
-		junk = o;
-		o->junked = true;
-		junked++;
+	if (!root->marked) {
+		ObjRefs_t *allrefs;
+		root->marked = true;
+		Sys_DPrintf ("GC: Marked %s@%p.\n", root->cl->name, root);
+		if (root->allRefs)
+			for (allrefs = methodCall(root, allRefs); allrefs; allrefs = allrefs->next) {
+				unsigned int i;
+				for (i = 0; i < allrefs->count; i++)
+					Garbage_Do_Mark (allrefs->objs[i]);
+			}
+	}
+}
+
+void
+Garbage_Do_Sweep (Object **allobjs)
+{
+	Object **prevNext;
+	Object *obj;
+
+	for (prevNext = allobjs, obj = *allobjs; obj; obj = *prevNext) {
+		if (obj->marked) {
+			obj->marked = false;
+			prevNext = &obj->next;
+		} else if (!obj->refs) {
+			*prevNext = obj->next;
+			obj->next = junk;
+			junk = obj;
+			junked++;
+			Sys_DPrintf ("GC: %s@%p is ready for disposal...\n", obj->cl->name, obj);
+		} else
+			*prevNext = obj->next;
 	}
 }
 
 unsigned int
-Garbage_Amount (void)
+Garbage_Pending (void)
 {
 	return junked;
 }
 
-
 void
-Garbage_Collect (unsigned int amount)
+Garbage_Dispose (unsigned int amount)
 {
-	Object *o;
+	Object *next;
 
-	if (!amount)
-		return;
-	Sys_DPrintf ("GC: Collecting %u objects...\n", amount);
-
-	for (o = junk; o && amount; o = junk) {
-		junk = o->next;
-		if (!o->refs) {
-			Sys_DPrintf("GC: Collecting %s@%p...\n", o->cl->name, o);
-			Object_Delete (o);
-			amount--;
-		} else {
-			Sys_DPrintf("GC: %s@%p gained references, not collecting...\n", o->cl->name, o);
-			o->junked = false;
-		}
+	for (; junk && amount; junk = next, amount--) {
+		next = junk->next;
+		Sys_DPrintf ("GC: Disposing of %s@%p...\n", junk->cl->name, junk);
+		Object_Delete (junk);
 		junked--;
 	}
-	junk = o;
 }

libs/object/object.c

@@ -58,6 +58,9 @@ static __attribute__ ((unused)) const char rcsid[] =
 #include "QF/classes/Integer.h"
 #include "QF/classes/Double.h"
 
+Object *allObjs = NULL;
+ArrayList *rootObj = NULL;
+
 static String *
 Object_ToString_f (Object *self) 
 {
@@ -67,6 +70,7 @@ Object_ToString_f (Object *self)
 static void
 Object_Init_f (Object *self) 
 {
+	self->allRefs = NULL;
 	self->toString = Object_ToString_f;
 	Sys_DPrintf("%s@%p initing...\n", self->cl->name, self);
 }
@@ -108,12 +112,13 @@ Object_Create (Class *cl, qboolean floating)
 {
 	Object *new = malloc (cl->size);
 	new->cl = cl;
-	new->junked = false;
 	if (floating) {
 		new->refs = 0;
-		Garbage_Junk_Object (new);
 	} else
 		new->refs = 1;
+	new->marked = false;
+	new->next = allObjs;
+	allObjs = new;
 	return new;
 }
 
@@ -135,8 +140,8 @@ Object_Retain (Object *obj)
 Object *
 Object_Release (Object *obj)
 {
-	if (obj->refs && --obj->refs == 0)
-		Garbage_Junk_Object (obj);
+	if (obj->refs)
+		obj->refs--;
 	return obj;
 }
 
@@ -150,6 +155,18 @@ Object_InstanceOf (Object *obj, Class *cl)
 	return false;
 }
 
+void
+Object_AddToRoot (Object *obj)
+{
+	methodCall(COLLECTION(rootObj), add, obj);
+}
+
+void
+Object_RemoveFromRoot (Object *obj)
+{
+	methodCall(COLLECTION(rootObj), remove, obj);
+}
+
 static void
 Object_Test (void)
 {
@@ -169,6 +186,12 @@ Object_Test (void)
 	methodCall(LIST(list), insertAt, 2, newFloat(String, "Mr. Two!"));
 	liststr = methodCall(OBJECT(list), toString);
 	Sys_DPrintf("List: %s\n", liststr->str);
+
+	list = newFloat(ArrayList, classObj(Object), NULL);
+	methodCall(list, add, newFloat(String, "Don't free me!"));
+	methodCall(list, add, newFloat(Integer, 5));
+	methodCall(list, add, newFloat(Double, 3.14));
+	Object_AddToRoot (OBJECT(methodCall(list, iterator)));
 }
 
 Class *Object_class;
@@ -206,7 +229,7 @@ Object_Init (void)
 		classInit(List);
 			classInit(ArrayList);
 	
-		
+	rootObj = new(ArrayList, classObj(Object), NULL);
 
 	/* Run test */
 	Object_Test();
@@ -215,7 +238,18 @@ Object_Init (void)
 void
 Object_Garbage_Collect (void)
 {
-	unsigned int amount;
-	if ((amount = Garbage_Amount()))
-		Garbage_Collect (amount / 2 + 1);
+	static unsigned int frames = 0;
+
+	frames++;
+
+	if (frames % 2000 == 0) {
+		Sys_DPrintf("GC: Marking...\n");
+		Garbage_Do_Mark (OBJECT(rootObj));
+		Sys_DPrintf("GC: Sweeping...\n");
+		Garbage_Do_Sweep (&allObjs);
+	}
+	if (frames % 50 == 0 && Garbage_Pending()) {
+		Sys_DPrintf("GC: Disposing...\n");
+		Garbage_Dispose (Garbage_Pending()/2 + 1);
+	}
 }

qw/source/sv_main.c

@@ -1907,13 +1907,13 @@ SV_GarbageCollect (void)
 		if (pr_gc_count >= pr_gc_interval->int_val) {
 			pr_gc_count = 0;
 			PR_GarbageCollect (&sv_pr_state);
-			Object_Garbage_Collect ();
 		}
 	} else {
 		// Make sure the count gets reset if the gc is disabled.  I
 		// could use a callback, but I'm lazy
 		pr_gc_count = 0;
 	}
+	Object_Garbage_Collect ();
 }
 
 void