added garbage collector draft

samples/makegarbage.noja

@@ -0,0 +1,10 @@
+
+i = 0;
+n = 10000000;
+
+while i < n:
+	{
+		1 + 1 * 1;
+		i = i + 1;
+		print('\r', 100.0 * i / n, '% ');
+	}

src/main.c

@@ -237,6 +237,8 @@ int main(int argc, char **argv)
 
 					Object *result = run(runtime, (Error*) &error, exe, 0, NULL, NULL, 0);
 
+					// NOTE: The `builtins` pointer is invalidated now.
+
 					if(result == NULL)
 						{
 							fprintf(stderr, "RUNTIME ERROR: %s.\n", error.base.message);

src/o_builtins.c

@@ -21,7 +21,7 @@ typedef struct {
 	Runtime *runtime;
 } BuiltinsMapOjbect;
 
-static const Type t_builtins_map = {
+static TypeObject t_builtins_map = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "builtins map",
 	.size = sizeof(BuiltinsMapOjbect),

src/o_net_builtins.c

@@ -32,7 +32,7 @@ typedef struct {
 	Runtime *runtime;
 } NetworkBuiltinsMapOjbect;
 
-static const Type t_builtins_map = {
+static TypeObject t_builtins_map = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "network builtins map",
 	.size = sizeof(NetworkBuiltinsMapOjbect),

src/objects/heap.c

@@ -17,8 +17,17 @@ struct OflowAlloc {
 struct xHeap {
 	int   size;
 	int   used;
+	int   total;
 	void *body;
 	OflowAlloc *oflow;
+
+	_Bool collecting;
+	_Bool collection_failed;
+	void *old_body;
+	int   old_used;
+	int   old_total;
+	OflowAlloc *old_oflow;
+	Error *error;
 };
 
 Heap *Heap_New(int size)
@@ -31,10 +40,12 @@ Heap *Heap_New(int size)
 	if(heap == NULL)
 		return NULL;
 
+	heap->total = 0;
 	heap->size = size;
 	heap->used = 0;
 	heap->body = malloc(size);
 	heap->oflow = 0;
+	heap->collecting = 0;
 
 	if(heap->body == NULL)
 		{
@@ -67,7 +78,12 @@ void Heap_Free(Heap *heap)
 	free(heap);
 }
 
-void *Heap_Malloc(Heap *heap, const Type *type, Error *err)
+float Heap_GetUsagePercentage(Heap *heap)
+{
+	return 100.0 * heap->total / heap->size;
+}
+
+void *Heap_Malloc(Heap *heap, TypeObject *type, Error *err)
 {
 	void *addr = Heap_RawMalloc(heap, type->size, err);
 
@@ -107,14 +123,20 @@ void *Heap_RawMalloc(Heap *heap, int size, Error *err)
 			heap->oflow = oflow;
 
 			addr = oflow->body;
+
+			heap->total += size;
 		}
 	else
 		{
+			int prev_used = heap->used;
+
 			if(heap->used & 7)
 				heap->used = (heap->used & ~7) + 8;
 
 			addr = heap->body + heap->used;
+
 			heap->used += size;
+			heap->total += heap->used - prev_used;
 		}
 
 	assert(((intptr_t) addr) % 8 == 0);
@@ -125,3 +147,149 @@ void *Heap_RawMalloc(Heap *heap, int size, Error *err)
 
 	return addr;
 }
+
+_Bool Heap_StartCollection(Heap *heap, Error *error)
+{
+	assert(heap->collecting == 0);
+
+	void *new_body = malloc(heap->size);
+
+	if(new_body == NULL)
+		{
+			Error_Report(error, 1, "No memory");
+			return 0;
+		}
+
+	heap->old_body = heap->body;
+	heap->old_used = heap->used;
+	heap->old_total = heap->total;
+	heap->old_oflow = heap->oflow;
+	heap->total = 0;
+	heap->body = new_body;
+	heap->used = 0;
+	heap->oflow = NULL;
+	heap->collecting = 1;
+	heap->collection_failed = 0;
+	heap->error = error;
+	return 1;
+}
+
+_Bool Heap_StopCollection(Heap *heap)
+{
+	assert(heap->collecting == 1);
+
+	if(heap->collection_failed)
+		{
+			free(heap->old_body);
+			return 0;
+		}
+
+	/* Call destructors here */
+
+	while(heap->old_oflow)
+		{
+			OflowAlloc *prev = heap->old_oflow->prev;
+			free(heap->old_oflow);
+			heap->old_oflow = prev;
+		}
+
+	free(heap->old_body);
+
+	heap->collecting = 0;
+	return 1;
+}
+
+void Heap_CollectExtension(void **referer, int size, Heap *heap)
+{
+	assert(referer != NULL);
+	assert(heap->collecting);
+
+	void *old_location = *referer;
+
+	if(heap->collection_failed || old_location == NULL)
+		return;
+
+	void *new_location = Heap_RawMalloc(heap, size, heap->error);
+
+	if(new_location == NULL)
+		{
+			heap->collection_failed = 1;
+			return;
+		}
+
+	memcpy(new_location, old_location, size);
+
+	*referer = new_location;
+}
+
+void Heap_CollectReference(Object **referer, Heap *heap)
+{
+	assert(referer != NULL);
+	assert(heap->collecting);
+
+	Object *old_location = *referer;
+
+	if(heap->collection_failed || old_location == NULL)
+		return;
+
+	Object *new_location;
+
+	if(old_location->flags & Object_STATIC)
+	
+		// The object doesn't need to be moved
+		// since it was statically allocated.
+		new_location = old_location;
+
+	else if(old_location->flags & Object_MOVED)
+	
+		// The object was already moved.
+		new_location = ((MovedObject*) old_location)->new_location;
+
+	else
+		{
+			// This object wasn't moved to
+			// the new heap yet.
+
+			// Get some information.
+			TypeObject *type = old_location->type;
+			int size         = type->size;
+
+			// Copy the object to a new location.
+			{
+				new_location = Heap_RawMalloc(heap, size, heap->error);
+
+				if(new_location == NULL)
+					{
+						heap->collection_failed = 1;
+						return;
+					}
+
+				memcpy(new_location, old_location, size);
+			}
+
+			// Set the old location as moved and
+			// leave the reference to the new
+			// location.
+			{
+				old_location->flags |= Object_MOVED;
+
+				assert((int) sizeof(MovedObject) <= size);
+				((MovedObject*) old_location)->new_location = new_location;
+			}
+		}
+
+	// Update the referer
+	*referer = new_location;
+
+	// Collect the reference to the type.
+	if((Object*) new_location->type != new_location)
+		Heap_CollectReference((Object**) &new_location->type, heap);
+
+	// Collect all of the references to
+	// extensions allocate using the GC'd
+	// heap.
+	Object_WalkExtensions(new_location, Heap_CollectExtension, heap);
+
+	// Now collect all of the children.
+	Object_WalkReferences(new_location, Heap_CollectReference, heap);
+}

src/objects/o_bool.c

@@ -5,7 +5,7 @@
 static _Bool to_bool(Object *obj, Error *err);
 static void print(Object *obj, FILE *fp);
 
-static const Type t_bool = {
+static TypeObject t_bool = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "bool",
 	.size = sizeof (Object),

src/objects/o_buffer.c

@@ -20,7 +20,7 @@ static _Bool   insert(Object *self, Object *key, Object *val, Heap *heap, Error
 static int     count(Object *self);
 static void	   print(Object *obj, FILE *fp);
 
-static const Type t_buffer = {
+static TypeObject t_buffer = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "buffer",
 	.size = sizeof (BufferObject),

src/objects/o_closure.c

@@ -9,13 +9,15 @@ struct ClosureObject {
 	Object        *vars;
 };
 
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp);
 static Object *select(Object *self, Object *key, Heap *heap, Error *err);
 
-static const Type t_closure = {
+static TypeObject t_closure = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "closure",
 	.size = sizeof(ClosureObject),
 	.select = select,
+	.walk = walk,
 };
 
 Object *Object_NewClosure(Object *parent, Object *new_map, Heap *heap, Error *error)
@@ -55,3 +57,11 @@ static Object *select(Object *self, Object *key, Heap *heap, Error *err)
 
 	return selected;
 }
+
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp)
+{
+	ClosureObject *closure = (ClosureObject*) self;
+
+	callback((Object**) &closure->prev, userp);
+	callback(&closure->vars, userp);
+}

src/objects/o_float.c

@@ -9,7 +9,7 @@ typedef struct {
 	double val;
 } FloatObject;
 
-static const Type t_float = {
+static TypeObject t_float = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "float",
 	.size = sizeof (FloatObject),

src/objects/o_int.c

@@ -11,7 +11,7 @@ typedef struct {
 	long long int val;
 } IntObject;
 
-static const Type t_int = {
+static TypeObject t_int = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "int",
 	.size = sizeof (IntObject),

src/objects/o_list.c

@@ -12,8 +12,10 @@ static Object *select(Object *self, Object *key, Heap *heap, Error *err);
 static _Bool   insert(Object *self, Object *key, Object *val, Heap *heap, Error *err);
 static int     count(Object *self);
 static void	   print(Object *obj, FILE *fp);
+static void    walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp);
+static void    walkexts(Object *self, void (*callback)(void   **referer, unsigned int size, void *userp), void *userp);
 
-static const Type t_list = {
+static TypeObject t_list = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "list",
 	.size = sizeof (ListObject),
@@ -21,6 +23,8 @@ static const Type t_list = {
 	.insert = insert,
 	.count = count,
 	.print = print,
+	.walk = walk,
+	.walkexts = walkexts,
 };
 
 static inline int calc_capacity(int mapper_size)
@@ -53,6 +57,21 @@ Object *Object_NewList(int capacity, Heap *heap, Error *error)
 	return (Object*) obj;
 }
 
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp)
+{
+	ListObject *list = (ListObject*) self;
+
+	for(int i = 0; i < list->count; i += 1)
+		callback(&list->vals[i], userp);
+}
+
+static void walkexts(Object *self, void (*callback)(void **referer, unsigned int size, void *userp), void *userp)
+{
+	ListObject *list = (ListObject*) self;
+	
+	callback((void**) &list->vals, sizeof(Object) * list->capacity, userp);
+}
+
 static Object *select(Object *self, Object *key, Heap *heap, Error *error)
 {
 	assert(self != NULL);

src/objects/o_map.c

@@ -14,8 +14,10 @@ static Object *select(Object *self, Object *key, Heap *heap, Error *err);
 static _Bool   insert(Object *self, Object *key, Object *val, Heap *heap, Error *err);
 static int     count(Object *self);
 static void	print(Object *self, FILE *fp);
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp);
+static void walkexts(Object *self, void (*callback)(void **referer, unsigned int size, void *userp), void *userp);
 
-static const Type t_map = {
+static TypeObject t_map = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "map",
 	.size = sizeof (MapObject),
@@ -23,6 +25,8 @@ static const Type t_map = {
 	.insert = insert,
 	.count = count,
 	.print = print,
+	.walk = walk,
+	.walkexts = walkexts,
 };
 
 static inline int calc_capacity(int mapper_size)
@@ -68,6 +72,26 @@ Object *Object_NewMap(int num, Heap *heap, Error *error)
 	return (Object*) obj;
 }
 
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp)
+{
+	MapObject *map = (MapObject*) self;
+
+	for(int i = 0; i < map->count; i += 1)
+		{
+			callback(&map->keys[i], userp);
+			callback(&map->vals[i], userp);
+		}
+}
+
+static void walkexts(Object *self, void (*callback)(void **referer, unsigned int size, void *userp), void *userp)
+{
+	MapObject *map = (MapObject*) self;
+	
+	callback((void**) &map->mapper, sizeof(int) * map->mapper_size, userp);
+	callback((void**) &map->keys, sizeof(Object) * calc_capacity(map->mapper_size), userp);
+	callback((void**) &map->vals, sizeof(Object) * calc_capacity(map->mapper_size), userp);
+}
+
 static Object *select(Object *self, Object *key, Heap *heap, Error *error)
 {
 	assert(self != NULL);

src/objects/o_none.c

@@ -5,7 +5,7 @@
 static _Bool op_eql(Object *self, Object *other);
 static void print(Object *obj, FILE *fp);
 
-static const Type t_none = {
+static TypeObject t_none = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "none",
 	.size = sizeof (Object),

src/objects/o_string.c

@@ -16,8 +16,9 @@ static Object *copy(Object *self, Heap *heap, Error *err);
 static void print(Object *obj, FILE *fp);
 static char *to_string(Object *self, int *size, Heap *heap, Error *err);
 static _Bool op_eql(Object *self, Object *other);
+static void walkexts(Object *self, void (*callback)(void **referer, unsigned int size, void *userp), void *userp);
 
-static const Type t_string = {
+static TypeObject t_string = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "string",
 	.atomic = ATMTP_STRING,
@@ -28,6 +29,7 @@ static const Type t_string = {
 	.print = print,
 	.to_string = to_string,
 	.op_eql = op_eql,
+	.walkexts = walkexts,
 };
 
 static char *to_string(Object *self, int *size, Heap *heap, Error *err)
@@ -128,3 +130,10 @@ static void print(Object *obj, FILE *fp)
 
 	fprintf(fp, "%.*s", str->size, str->body);
 }
+
+static void walkexts(Object *self, void (*callback)(void **referer, unsigned int size, void *userp), void *userp)
+{
+	StringObject *str = (StringObject*) self;
+	
+	callback((void**) &str->body, str->size+1, userp);
+}

src/objects/objects.c

@@ -2,17 +2,17 @@
 #include "../utils/defs.h"
 #include "objects.h"
 
-const Type t_type = {
+TypeObject t_type = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "type",
-	.size = sizeof (Type),
+	.size = sizeof (TypeObject),
 };
 
 const char *Object_GetName(const Object *obj)
 {
 	assert(obj != NULL);
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	const char *name = type->name;
@@ -21,7 +21,7 @@ const char *Object_GetName(const Object *obj)
 	return name;
 }
 
-const Type *Object_GetType(const Object *obj)
+const TypeObject *Object_GetType(const Object *obj)
 {
 	assert(obj != NULL);
 	assert(obj->type != NULL);
@@ -33,7 +33,7 @@ unsigned int Object_GetSize(const Object *obj, Error *err)
 	assert(err != NULL);
 	assert(obj != NULL);
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	return type->size;
@@ -44,7 +44,7 @@ unsigned int Object_GetDeepSize(const Object *obj, Error *err)
 	assert(err != NULL);
 	assert(obj != NULL);
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	if(type->deepsize == NULL)
@@ -60,7 +60,7 @@ int Object_Hash(Object *obj, Error *err)
 {
 	assert(obj != NULL);
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type != NULL);
 
 	if(type->hash == NULL)
@@ -77,7 +77,7 @@ Object *Object_Copy(Object *obj, Heap *heap, Error *err)
 	assert(err != NULL);
 	assert(obj != NULL);
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type != NULL);
 
 	if(type->copy == NULL)
@@ -94,7 +94,7 @@ Object *Object_Call(Object *obj, Object **argv, unsigned int argc, Heap *heap, E
 	assert(err);
 	assert(obj);
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	if(type->call == NULL)
@@ -110,7 +110,7 @@ void Object_Print(Object *obj, FILE *fp)
 {
 	assert(obj != NULL);
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	if(type->print == NULL)
@@ -125,7 +125,7 @@ Object *Object_Select(Object *coll, Object *key, Heap *heap, Error *err)
 	assert(key);
 	assert(coll);
 
-	const Type *type = Object_GetType(coll);
+	const TypeObject *type = Object_GetType(coll);
 	assert(type);
 
 	if(type->select == NULL)
@@ -143,7 +143,7 @@ Object *Object_Delete(Object *coll, Object *key, Heap *heap, Error *err)
 	assert(key);
 	assert(coll);
 
-	const Type *type = Object_GetType(coll);
+	const TypeObject *type = Object_GetType(coll);
 	assert(type);
 
 	if(type->delete == NULL)
@@ -161,7 +161,7 @@ _Bool Object_Insert(Object *coll, Object *key, Object *val, Heap *heap, Error *e
 	assert(key);
 	assert(coll);
 
-	const Type *type = Object_GetType(coll);
+	const TypeObject *type = Object_GetType(coll);
 	assert(type);
 
 	if(type->insert == NULL)
@@ -178,7 +178,7 @@ int	Object_Count(Object *coll, Error *err)
 	assert(err);
 	assert(coll);
 
-	const Type *type = Object_GetType(coll);
+	const TypeObject *type = Object_GetType(coll);
 	assert(type);
 
 	if(type->count == NULL)
@@ -195,7 +195,7 @@ Object *Object_Next(Object *iter, Heap *heap, Error *err)
 	assert(err);
 	assert(iter);
 
-	const Type *type = Object_GetType(iter);
+	const TypeObject *type = Object_GetType(iter);
 	assert(type);
 
 	if(type->next == NULL)
@@ -212,7 +212,7 @@ Object *Object_Prev(Object *iter, Heap *heap, Error *err)
 	assert(err);
 	assert(iter);
 
-	const Type *type = Object_GetType(iter);
+	const TypeObject *type = Object_GetType(iter);
 	assert(type);
 
 	if(type->prev == NULL)
@@ -263,7 +263,7 @@ long long int Object_ToInt(Object *obj, Error *err)
 			return 0;
 		}
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	if(type->to_int == NULL)
@@ -286,7 +286,7 @@ _Bool Object_ToBool(Object *obj, Error *err)
 			return 0;
 		}
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	if(type->to_bool == NULL)
@@ -309,7 +309,7 @@ double Object_ToFloat(Object *obj, Error *err)
 			return 0;
 		}
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	if(type->to_float == NULL)
@@ -332,7 +332,7 @@ const char *Object_ToString(Object *obj, int *size, Heap *heap, Error *err)
 			return NULL;
 		}
 
-	const Type *type = Object_GetType(obj);
+	const TypeObject *type = Object_GetType(obj);
 	assert(type);
 
 	if(type->to_string == NULL)
@@ -361,3 +361,15 @@ _Bool Object_Compare(Object *obj1, Object *obj2, Error *error)
 
 	return obj1->type->op_eql(obj1, obj2);
 }
+
+void Object_WalkReferences(Object *parent, void (*callback)(Object **referer, void *userp), void *userp)
+{
+	if(parent->type->walk != NULL)
+		parent->type->walk(parent, callback, userp);
+}
+
+void Object_WalkExtensions(Object *parent, void (*callback)(void **referer, unsigned int size, void *userp), void *userp)
+{
+	if(parent->type->walkexts != NULL)
+		parent->type->walkexts(parent, callback, userp);
+}

src/objects/objects.h

@@ -4,15 +4,20 @@
 #include <stdio.h>
 #include "../utils/error.h"
 
-typedef struct Type Type;
+typedef struct TypeObject TypeObject;
 typedef struct Object Object;
 typedef struct xHeap Heap;
 
 struct Object {
-	const Type *type;
+	TypeObject *type;
 	unsigned int flags;
 };
 
+typedef struct {
+	Object base;
+	Object *new_location;
+} MovedObject;
+
 typedef enum {
 	ATMTP_NOTATOMIC = 0,
 	ATMTP_INT,
@@ -21,7 +26,7 @@ typedef enum {
 	ATMTP_STRING,
 } AtomicType;
 
-struct Type {
+struct TypeObject {
 
 	Object base;
 	
@@ -57,18 +62,27 @@ struct Type {
 	};
 
 	_Bool (*op_eql)(Object *self, Object *other);
+
+	// All.
+	void (*walk)    (Object *self, void (*callback)(Object **referer,                    void *userp), void *userp);
+	void (*walkexts)(Object *self, void (*callback)(void   **referer, unsigned int size, void *userp), void *userp);
 };
 
 enum {
 	Object_STATIC = 1,
+	Object_MOVED  = 2,
 };
 
 Heap*		 Heap_New(int size);
 void		 Heap_Free(Heap *heap);
-void*		 Heap_Malloc   (Heap *heap, const Type *type, Error *err);
+void*		 Heap_Malloc   (Heap *heap, TypeObject *type, Error *err);
 void*		 Heap_RawMalloc(Heap *heap, int size, Error *err);
+_Bool 	 	 Heap_StartCollection(Heap *heap, Error *error);
+_Bool 	  	 Heap_StopCollection(Heap *heap);
+void  	 	 Heap_CollectReference(Object **referer, Heap *heap);
+float 		 Heap_GetUsagePercentage(Heap *heap);
 
-const Type*	 Object_GetType(const Object *obj);
+const TypeObject* Object_GetType(const Object *obj);
 const char*	 Object_GetName(const Object *obj);
 unsigned int Object_GetSize(const Object *obj, Error *err);
 unsigned int Object_GetDeepSize(const Object *obj, Error *err);
@@ -83,6 +97,8 @@ _Bool		 Object_Insert(Object *coll, Object *key, Object *val, Heap *heap, Error
 int 		 Object_Count (Object *coll, Error *err);
 Object*		 Object_Next  (Object *iter, Heap *heap, Error *err);
 Object*		 Object_Prev  (Object *iter, Heap *heap, Error *err);
+void 		 Object_WalkReferences(Object *parent, void (*callback)(Object **referer,                    void *userp), void *userp);
+void 		 Object_WalkExtensions(Object *parent, void (*callback)(void   **referer, unsigned int size, void *userp), void *userp);
 
 Object*		 Object_NewMap(int num, Heap *heap, Error *error);
 Object*		 Object_NewList(int capacity, Heap *heap, Error *error);
@@ -108,5 +124,5 @@ const char	 *Object_ToString(Object *obj, int *size, Heap *heap, Error *err);
 
 _Bool 		  Object_Compare(Object *obj1, Object *obj2, Error *error);
 
-extern const Type t_type;
+extern TypeObject t_type;
 #endif

src/runtime/o_func.c

@@ -13,14 +13,22 @@ typedef struct {
 } FunctionObject;
 
 static Object *call(Object *self, Object **argv, unsigned int argc, Heap *heap, Error *error);
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp);
 
-static const Type t_func = {
+static TypeObject t_func = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "function",
 	.size = sizeof (FunctionObject),
 	.call = call,
+	.walk = walk,
 };
 
+static void walk(Object *self, void (*callback)(Object **referer, void *userp), void *userp)
+{
+	FunctionObject *func = (FunctionObject*) self;
+	callback(&func->closure, userp);
+}
+
 static Object *call(Object *self, Object **argv, unsigned int argc, Heap *heap, Error *error)
 {
 	assert(self != NULL);

src/runtime/o_nfunc.c

@@ -13,7 +13,7 @@ typedef struct {
 
 static Object *call(Object *self, Object **argv, unsigned int argc, Heap *heap, Error *error);
 
-static const Type t_nfunc = {
+static TypeObject t_nfunc = {
 	.base = (Object) { .type = &t_type, .flags = Object_STATIC },
 	.name = "native function",
 	.size = sizeof (NativeFunctionObject),

src/runtime/runtime.c

@@ -1032,6 +1032,33 @@ static _Bool step(Runtime *runtime, Error *error)
 	return 1;
 }
 
+static _Bool collect(Runtime *runtime, Error *error)
+{
+	Frame *frame = runtime->frame;
+
+	if(!Heap_StartCollection(runtime->heap, error))
+		return 0;
+
+	Heap_CollectReference(&runtime->builtins,  runtime->heap);
+
+	while(frame)
+		{
+			Heap_CollectReference(&frame->locals,  runtime->heap);
+			Heap_CollectReference(&frame->closure, runtime->heap);
+			frame = frame->prev;
+		}
+
+	for(unsigned int i = 0; i < Stack_Size(runtime->stack); i += 1)
+		{
+			Object **ref = (Object**) Stack_TopRef(runtime->stack, -i);
+			assert(ref != NULL);
+
+			Heap_CollectReference(ref, runtime->heap);
+		}
+
+	return Heap_StopCollection(runtime->heap);
+}
+
 Object *run(Runtime *runtime, Error *error, Executable *exe, int index, Object *closure, Object **argv, int argc)
 {
 	assert(runtime != NULL);
@@ -1086,14 +1113,29 @@ Object *run(Runtime *runtime, Error *error, Executable *exe, int index, Object *
 				Error_Report(error, 0, "Forced abortion");
 			else
 				while(step(runtime, error))
+					{
 						if(!runtime->callback_addr(runtime, runtime->callback_userp))
 							{
 								Error_Report(error, 0, "Forced abortion");
 								break;
 							}
+
+						//printf("%2.2f%% percent.\n", Heap_GetUsagePercentage(runtime->heap));
+
+						if(Heap_GetUsagePercentage(runtime->heap) > 100)
+							if(!collect(runtime, error))
+								break;
+					}
 		}
 	else
-		while(step(runtime, error));
+		while(step(runtime, error))
+			{
+				if(Heap_GetUsagePercentage(runtime->heap) > 100)
+					if(!collect(runtime, error))
+						break;
+
+				//printf("%2.2f%% percent.\n", Heap_GetUsagePercentage(runtime->heap));
+			}
 
 	// This is what the function will return.
 	Object *result = NULL;

src/utils/stack.c

@@ -54,6 +54,26 @@ void *Stack_Top(Stack *s, int n)
 	return s->body[s->used + n - 1];
 }
 
+void **Stack_TopRef(Stack *s, int n)
+{
+	assert(n <= 0);
+
+	if(Stack_IsReadOnlyCopy(s))
+		return NULL;
+
+	// Remove readonly bit.
+	s = unmark(s);
+
+	if(s->used == 0)
+		return NULL;
+
+	if((int) s->used + n - 1 < 0)
+		return NULL;
+
+	return &s->body[s->used + n - 1];
+}
+
+
 _Bool Stack_Pop(Stack *s, unsigned int n)
 {
 	if(Stack_IsReadOnlyCopy(s))

src/utils/stack.h

@@ -8,6 +8,7 @@ _Bool 		 Stack_Push(Stack *s, void *item);
 void 		 Stack_Free(Stack *s);
 unsigned int Stack_Size(Stack *s);
 Stack 		*Stack_Copy(Stack *s, _Bool readonly);
+void       **Stack_TopRef(Stack *s, int n);
 unsigned int Stack_Capacity(Stack *s);
 _Bool		 Stack_IsReadOnlyCopy(Stack *s);
 #endif