Fix #7513: recursive garbage collection caused stack overflow

src/3rdparty/squirrel/squirrel/sqarray.h

@@ -17,7 +17,7 @@ struct SQArray : public CHAINABLE_OBJ
 		return newarray;
 	}
 #ifndef NO_GARBAGE_COLLECTOR
-	void Mark(SQCollectable **chain);
+	void EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue);
 #endif
 	void Finalize(){
 		_values.resize(0);

src/3rdparty/squirrel/squirrel/sqclass.h

@@ -59,7 +59,7 @@ struct SQClass : public CHAINABLE_OBJ
 	}
 	void Finalize();
 #ifndef NO_GARBAGE_COLLECTOR
-	void Mark(SQCollectable ** );
+	void EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue);
 #endif
 	SQInteger Next(const SQObjectPtr &refpos, SQObjectPtr &outkey, SQObjectPtr &outval);
 	SQInstance *CreateInstance();
@@ -147,7 +147,7 @@ struct SQInstance : public SQDelegable
 	}
 	void Finalize();
 #ifndef NO_GARBAGE_COLLECTOR
-	void Mark(SQCollectable ** );
+	void EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue);
 #endif
 	bool InstanceOf(SQClass *trg);
 	bool GetMetaMethod(SQVM *v,SQMetaMethod mm,SQObjectPtr &res);

src/3rdparty/squirrel/squirrel/sqclosure.h

@@ -32,7 +32,7 @@ struct SQClosure : public CHAINABLE_OBJ
 	bool Save(SQVM *v,SQUserPointer up,SQWRITEFUNC write);
 	static bool Load(SQVM *v,SQUserPointer up,SQREADFUNC read,SQObjectPtr &ret);
 #ifndef NO_GARBAGE_COLLECTOR
-	void Mark(SQCollectable **chain);
+	void EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue);
 	void Finalize(){_outervalues.resize(0); }
 #endif
 	SQObjectPtr _env;
@@ -66,7 +66,7 @@ struct SQGenerator : public CHAINABLE_OBJ
 	bool Yield(SQVM *v);
 	bool Resume(SQVM *v,SQInteger target);
 #ifndef NO_GARBAGE_COLLECTOR
-	void Mark(SQCollectable **chain);
+	void EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue);
 	void Finalize(){_stack.resize(0);_closure=_null_;}
 #endif
 	SQObjectPtr _closure;
@@ -106,7 +106,7 @@ struct SQNativeClosure : public CHAINABLE_OBJ
 		sq_delete(this,SQNativeClosure);
 	}
 #ifndef NO_GARBAGE_COLLECTOR
-	void Mark(SQCollectable **chain);
+	void EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue);
 	void Finalize(){_outervalues.resize(0);}
 #endif
 	SQInteger _nparamscheck;

src/3rdparty/squirrel/squirrel/sqobject.cpp

@@ -486,104 +486,81 @@ bool SQFunctionProto::Load(SQVM *v,SQUserPointer up,SQREADFUNC read,SQObjectPtr
 
 #ifndef NO_GARBAGE_COLLECTOR
 
-#define START_MARK() 	if(!(_uiRef&MARK_FLAG)){ \
-		_uiRef|=MARK_FLAG;
-
-#define END_MARK() RemoveFromChain(&_sharedstate->_gc_chain, this); \
-		AddToChain(chain, this); }
-
-void SQVM::Mark(SQCollectable **chain)
+void SQVM::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue)
 {
-	START_MARK()
-		SQSharedState::MarkObject(_lasterror,chain);
-		SQSharedState::MarkObject(_errorhandler,chain);
-		SQSharedState::MarkObject(_debughook,chain);
-		SQSharedState::MarkObject(_roottable, chain);
-		SQSharedState::MarkObject(temp_reg, chain);
-		for(SQUnsignedInteger i = 0; i < _stack.size(); i++) SQSharedState::MarkObject(_stack[i], chain);
-		for(SQUnsignedInteger j = 0; j < _vargsstack.size(); j++) SQSharedState::MarkObject(_vargsstack[j], chain);
-		for(SQInteger k = 0; k < _callsstacksize; k++) SQSharedState::MarkObject(_callsstack[k]._closure, chain);
-	END_MARK()
-}
-
-void SQArray::Mark(SQCollectable **chain)
+	SQSharedState::EnqueueMarkObject(_lasterror,queue);
+	SQSharedState::EnqueueMarkObject(_errorhandler,queue);
+	SQSharedState::EnqueueMarkObject(_debughook,queue);
+	SQSharedState::EnqueueMarkObject(_roottable, queue);
+	SQSharedState::EnqueueMarkObject(temp_reg, queue);
+	for(SQUnsignedInteger i = 0; i < _stack.size(); i++) SQSharedState::EnqueueMarkObject(_stack[i], queue);
+	for(SQUnsignedInteger j = 0; j < _vargsstack.size(); j++) SQSharedState::EnqueueMarkObject(_vargsstack[j], queue);
+	for(SQInteger k = 0; k < _callsstacksize; k++) SQSharedState::EnqueueMarkObject(_callsstack[k]._closure, queue);
+}
+
+void SQArray::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue)
 {
-	START_MARK()
-		SQInteger len = _values.size();
-		for(SQInteger i = 0;i < len; i++) SQSharedState::MarkObject(_values[i], chain);
-	END_MARK()
+	SQInteger len = _values.size();
+	for(SQInteger i = 0;i < len; i++) SQSharedState::EnqueueMarkObject(_values[i], queue);
 }
-void SQTable::Mark(SQCollectable **chain)
+
+void SQTable::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue)
 {
-	START_MARK()
-		if(_delegate) _delegate->Mark(chain);
-		SQInteger len = _numofnodes;
-		for(SQInteger i = 0; i < len; i++){
-			SQSharedState::MarkObject(_nodes[i].key, chain);
-			SQSharedState::MarkObject(_nodes[i].val, chain);
-		}
-	END_MARK()
+	if(_delegate) queue.Enqueue(_delegate);
+	SQInteger len = _numofnodes;
+	for(SQInteger i = 0; i < len; i++){
+		SQSharedState::EnqueueMarkObject(_nodes[i].key, queue);
+		SQSharedState::EnqueueMarkObject(_nodes[i].val, queue);
+	}
 }
 
-void SQClass::Mark(SQCollectable **chain)
+void SQClass::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue)
 {
-	START_MARK()
-		_members->Mark(chain);
-		if(_base) _base->Mark(chain);
-		SQSharedState::MarkObject(_attributes, chain);
-		for(SQUnsignedInteger i =0; i< _defaultvalues.size(); i++) {
-			SQSharedState::MarkObject(_defaultvalues[i].val, chain);
-			SQSharedState::MarkObject(_defaultvalues[i].attrs, chain);
-		}
-		for(SQUnsignedInteger j =0; j< _methods.size(); j++) {
-			SQSharedState::MarkObject(_methods[j].val, chain);
-			SQSharedState::MarkObject(_methods[j].attrs, chain);
-		}
-		for(SQUnsignedInteger k =0; k< _metamethods.size(); k++) {
-			SQSharedState::MarkObject(_metamethods[k], chain);
-		}
-	END_MARK()
+	queue.Enqueue(_members);
+	if(_base) queue.Enqueue(_base);
+	SQSharedState::EnqueueMarkObject(_attributes, queue);
+	for(SQUnsignedInteger i =0; i< _defaultvalues.size(); i++) {
+		SQSharedState::EnqueueMarkObject(_defaultvalues[i].val, queue);
+		SQSharedState::EnqueueMarkObject(_defaultvalues[i].attrs, queue);
+	}
+	for(SQUnsignedInteger j =0; j< _methods.size(); j++) {
+		SQSharedState::EnqueueMarkObject(_methods[j].val, queue);
+		SQSharedState::EnqueueMarkObject(_methods[j].attrs, queue);
+	}
+	for(SQUnsignedInteger k =0; k< _metamethods.size(); k++) {
+		SQSharedState::EnqueueMarkObject(_metamethods[k], queue);
+	}
 }
 
-void SQInstance::Mark(SQCollectable **chain)
+void SQInstance::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue)
 {
-	START_MARK()
-		_class->Mark(chain);
-		SQUnsignedInteger nvalues = _class->_defaultvalues.size();
-		for(SQUnsignedInteger i =0; i< nvalues; i++) {
-			SQSharedState::MarkObject(_values[i], chain);
-		}
-	END_MARK()
+	queue.Enqueue(_class);
+	SQUnsignedInteger nvalues = _class->_defaultvalues.size();
+	for(SQUnsignedInteger i =0; i< nvalues; i++) {
+		SQSharedState::EnqueueMarkObject(_values[i], queue);
+	}
 }
 
-void SQGenerator::Mark(SQCollectable **chain)
+void SQGenerator::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue)
 {
-	START_MARK()
-		for(SQUnsignedInteger i = 0; i < _stack.size(); i++) SQSharedState::MarkObject(_stack[i], chain);
-		for(SQUnsignedInteger j = 0; j < _vargsstack.size(); j++) SQSharedState::MarkObject(_vargsstack[j], chain);
-		SQSharedState::MarkObject(_closure, chain);
-	END_MARK()
+	for(SQUnsignedInteger i = 0; i < _stack.size(); i++) SQSharedState::EnqueueMarkObject(_stack[i], queue);
+	for(SQUnsignedInteger j = 0; j < _vargsstack.size(); j++) SQSharedState::EnqueueMarkObject(_vargsstack[j], queue);
+	SQSharedState::EnqueueMarkObject(_closure, queue);
 }
 
-void SQClosure::Mark(SQCollectable **chain)
+void SQClosure::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue)
 {
-	START_MARK()
-		for(SQUnsignedInteger i = 0; i < _outervalues.size(); i++) SQSharedState::MarkObject(_outervalues[i], chain);
-		for(SQUnsignedInteger i = 0; i < _defaultparams.size(); i++) SQSharedState::MarkObject(_defaultparams[i], chain);
-	END_MARK()
+	for(SQUnsignedInteger i = 0; i < _outervalues.size(); i++) SQSharedState::EnqueueMarkObject(_outervalues[i], queue);
+	for(SQUnsignedInteger i = 0; i < _defaultparams.size(); i++) SQSharedState::EnqueueMarkObject(_defaultparams[i], queue);
 }
 
-void SQNativeClosure::Mark(SQCollectable **chain)
+void SQNativeClosure::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue)
 {
-	START_MARK()
-		for(SQUnsignedInteger i = 0; i < _outervalues.size(); i++) SQSharedState::MarkObject(_outervalues[i], chain);
-	END_MARK()
+	for(SQUnsignedInteger i = 0; i < _outervalues.size(); i++) SQSharedState::EnqueueMarkObject(_outervalues[i], queue);
 }
 
-void SQUserData::Mark(SQCollectable **chain){
-	START_MARK()
-		if(_delegate) _delegate->Mark(chain);
-	END_MARK()
+void SQUserData::EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue){
+	if(_delegate) queue.Enqueue(_delegate);
 }
 
 void SQCollectable::UnMark() { _uiRef&=~MARK_FLAG; }

src/3rdparty/squirrel/squirrel/sqobject.h

@@ -2,6 +2,7 @@
 #ifndef _SQOBJECT_H_
 #define _SQOBJECT_H_
 
+#include <forward_list>
 #include "squtils.h"
 
 #define SQ_CLOSURESTREAM_HEAD (('S'<<24)|('Q'<<16)|('I'<<8)|('R'))
@@ -344,13 +345,48 @@ struct SQCollectable : public SQRefCounted {
 	SQCollectable *_prev;
 	SQSharedState *_sharedstate;
 	virtual void Release()=0;
-	virtual void Mark(SQCollectable **chain)=0;
+	virtual void EnqueueMarkObjectForChildren(class SQGCMarkerQueue &queue)=0;
 	void UnMark();
 	virtual void Finalize()=0;
 	static void AddToChain(SQCollectable **chain,SQCollectable *c);
 	static void RemoveFromChain(SQCollectable **chain,SQCollectable *c);
 };
 
+/**
+ * Helper container for state to change the garbage collection from a recursive to an iterative approach.
+ * The iterative approach provides effectively a depth first search approach.
+ */
+class SQGCMarkerQueue {
+	std::forward_list<SQCollectable*> queue; ///< The queue of elements to still process.
+public:
+	/** Whether there are any elements left to process. */
+	bool IsEmpty() { return this->queue.empty(); }
+
+	/**
+	 * Remove the first element from the queue.
+	 * Removal when the queue is empty results in undefined behaviour.
+	 */
+	SQCollectable *Pop()
+	{
+		SQCollectable *collectable = this->queue.front();
+		this->queue.pop_front();
+		return collectable;
+	}
+
+	/**
+	 * Add a collectable to the queue, but only when it has not been marked yet.
+	 * When adding it to the queue, the collectable will be marked, so subsequent calls
+	 * will not add it again.
+	 */
+	void Enqueue(SQCollectable *collectable)
+	{
+		if ((collectable->_uiRef & MARK_FLAG) == 0) {
+			collectable->_uiRef |= MARK_FLAG;
+			this->queue.push_front(collectable);
+		}
+	}
+};
+
 
 #define ADD_TO_CHAIN(chain,obj) AddToChain(chain,obj)
 #define REMOVE_FROM_CHAIN(chain,obj) {if(!(_uiRef&MARK_FLAG))RemoveFromChain(chain,obj);}

src/3rdparty/squirrel/squirrel/sqstate.cpp

@@ -228,18 +228,18 @@ SQInteger SQSharedState::GetMetaMethodIdxByName(const SQObjectPtr &name)
 
 #ifndef NO_GARBAGE_COLLECTOR
 
-void SQSharedState::MarkObject(SQObjectPtr &o,SQCollectable **chain)
+void SQSharedState::EnqueueMarkObject(SQObjectPtr &o,SQGCMarkerQueue &queue)
 {
 	switch(type(o)){
-	case OT_TABLE:_table(o)->Mark(chain);break;
-	case OT_ARRAY:_array(o)->Mark(chain);break;
-	case OT_USERDATA:_userdata(o)->Mark(chain);break;
-	case OT_CLOSURE:_closure(o)->Mark(chain);break;
-	case OT_NATIVECLOSURE:_nativeclosure(o)->Mark(chain);break;
-	case OT_GENERATOR:_generator(o)->Mark(chain);break;
-	case OT_THREAD:_thread(o)->Mark(chain);break;
-	case OT_CLASS:_class(o)->Mark(chain);break;
-	case OT_INSTANCE:_instance(o)->Mark(chain);break;
+	case OT_TABLE:queue.Enqueue(_table(o));break;
+	case OT_ARRAY:queue.Enqueue(_array(o));break;
+	case OT_USERDATA:queue.Enqueue(_userdata(o));break;
+	case OT_CLOSURE:queue.Enqueue(_closure(o));break;
+	case OT_NATIVECLOSURE:queue.Enqueue(_nativeclosure(o));break;
+	case OT_GENERATOR:queue.Enqueue(_generator(o));break;
+	case OT_THREAD:queue.Enqueue(_thread(o));break;
+	case OT_CLASS:queue.Enqueue(_class(o));break;
+	case OT_INSTANCE:queue.Enqueue(_instance(o));break;
 	default: break; //shutup compiler
 	}
 }
@@ -248,27 +248,36 @@ void SQSharedState::MarkObject(SQObjectPtr &o,SQCollectable **chain)
 SQInteger SQSharedState::CollectGarbage(SQVM *vm)
 {
 	SQInteger n=0;
-	SQCollectable *tchain=NULL;
 	SQVM *vms = _thread(_root_vm);
 
-	vms->Mark(&tchain);
+	SQGCMarkerQueue queue;
+	queue.Enqueue(vms);
 #ifdef WITH_ASSERT
 	SQInteger x = _table(_thread(_root_vm)->_roottable)->CountUsed();
 #endif
-	_refs_table.Mark(&tchain);
-	MarkObject(_registry,&tchain);
-	MarkObject(_consts,&tchain);
-	MarkObject(_metamethodsmap,&tchain);
-	MarkObject(_table_default_delegate,&tchain);
-	MarkObject(_array_default_delegate,&tchain);
-	MarkObject(_string_default_delegate,&tchain);
-	MarkObject(_number_default_delegate,&tchain);
-	MarkObject(_generator_default_delegate,&tchain);
-	MarkObject(_thread_default_delegate,&tchain);
-	MarkObject(_closure_default_delegate,&tchain);
-	MarkObject(_class_default_delegate,&tchain);
-	MarkObject(_instance_default_delegate,&tchain);
-	MarkObject(_weakref_default_delegate,&tchain);
+	_refs_table.EnqueueMarkObject(queue);
+	EnqueueMarkObject(_registry,queue);
+	EnqueueMarkObject(_consts,queue);
+	EnqueueMarkObject(_metamethodsmap,queue);
+	EnqueueMarkObject(_table_default_delegate,queue);
+	EnqueueMarkObject(_array_default_delegate,queue);
+	EnqueueMarkObject(_string_default_delegate,queue);
+	EnqueueMarkObject(_number_default_delegate,queue);
+	EnqueueMarkObject(_generator_default_delegate,queue);
+	EnqueueMarkObject(_thread_default_delegate,queue);
+	EnqueueMarkObject(_closure_default_delegate,queue);
+	EnqueueMarkObject(_class_default_delegate,queue);
+	EnqueueMarkObject(_instance_default_delegate,queue);
+	EnqueueMarkObject(_weakref_default_delegate,queue);
+
+	SQCollectable *tchain=NULL;
+
+	while (!queue.IsEmpty()) {
+		SQCollectable *q = queue.Pop();
+		q->EnqueueMarkObjectForChildren(queue);
+		SQCollectable::RemoveFromChain(&_gc_chain, q);
+		SQCollectable::AddToChain(&tchain, q);
+	}
 
 	SQCollectable *t = _gc_chain;
 	SQCollectable *nx = NULL;
@@ -357,12 +366,12 @@ RefTable::~RefTable()
 }
 
 #ifndef NO_GARBAGE_COLLECTOR
-void RefTable::Mark(SQCollectable **chain)
+void RefTable::EnqueueMarkObject(SQGCMarkerQueue &queue)
 {
 	RefNode *nodes = (RefNode *)_nodes;
 	for(SQUnsignedInteger n = 0; n < _numofslots; n++) {
 		if(type(nodes->obj) != OT_NULL) {
-			SQSharedState::MarkObject(nodes->obj,chain);
+			SQSharedState::EnqueueMarkObject(nodes->obj,queue);
 		}
 		nodes++;
 	}

src/3rdparty/squirrel/squirrel/sqstate.h

@@ -34,7 +34,7 @@ struct RefTable {
 	void AddRef(SQObject &obj);
 	SQBool Release(SQObject &obj);
 #ifndef NO_GARBAGE_COLLECTOR
-	void Mark(SQCollectable **chain);
+	void EnqueueMarkObject(SQGCMarkerQueue &queue);
 #endif
 	void Finalize();
 private:
@@ -63,7 +63,7 @@ struct SQSharedState
 	SQInteger GetMetaMethodIdxByName(const SQObjectPtr &name);
 #ifndef NO_GARBAGE_COLLECTOR
 	SQInteger CollectGarbage(SQVM *vm);
-	static void MarkObject(SQObjectPtr &o,SQCollectable **chain);
+	static void EnqueueMarkObject(SQObjectPtr &o,SQGCMarkerQueue &queue);
 #endif
 	SQObjectPtrVec *_metamethods;
 	SQObjectPtr _metamethodsmap;

src/3rdparty/squirrel/squirrel/sqtable.h

@@ -60,7 +60,7 @@ struct SQTable : public SQDelegable
 		SQ_FREE(_nodes, _numofnodes * sizeof(_HashNode));
 	}
 #ifndef NO_GARBAGE_COLLECTOR
-	void Mark(SQCollectable **chain);
+	void EnqueueMarkObjectForChildren(SQGCMarkerQueue &queue);
 #endif
 	inline _HashNode *_Get(const SQObjectPtr &key,SQHash hash)
 	{