Don't leak references to Strings on script errors (#583)

src/script/C4AulParse.cpp

@@ -1075,7 +1075,7 @@ C4V_Type C4AulParse::GetLastRetType(C4V_Type to)
 
 C4AulBCC C4AulParse::MakeSetter(bool fLeaveValue)
 {
-	if(Type != PARSER) { C4AulBCC Dummy; Dummy.bccType = AB_ERR; return Dummy; }
+	if(Type != PARSER) { return C4AulBCC(AB_ERR, 0); }
 	C4AulBCC Value = *(Fn->GetLastCode()), Setter = Value;
 	// Check type
 	switch (Value.bccType)
@@ -1090,11 +1090,9 @@ C4AulBCC C4AulParse::MakeSetter(bool fLeaveValue)
 	case AB_STACK_SET: Setter.bccType = AB_STACK_SET; break;
 	case AB_LOCALN:
 		Setter.bccType = AB_LOCALN_SET;
-		Setter.Par.s->IncRef(); // so string isn't dropped by RemoveLastBCC, see also C4AulScript::AddBCC
 		break;
 	case AB_PROP:
 		Setter.bccType = AB_PROP_SET;
-		Setter.Par.s->IncRef(); // so string isn't dropped by RemoveLastBCC, see also C4AulScript::AddBCC
 		break;
 	case AB_GLOBALN: Setter.bccType = AB_GLOBALN_SET; break;
 	default: 
@@ -2391,15 +2389,17 @@ void C4AulParse::Parse_Expression(int iParentPrio)
 				Fn->GetLastCode()->Par.i = - Fn->GetLastCode()->Par.i;
 				break;
 			}
-		// changer? make a setter BCC, leave value for operator
-		C4AulBCC Changer;
-		if(op->Changer)
-			Changer = MakeSetter(true);
-		// write byte code
-		AddBCC(op->Code, 0);
-		// writter setter
-		if(op->Changer)
-			AddBCC(Changer.bccType, Changer.Par.X);
+		{
+			// changer? make a setter BCC, leave value for operator
+			C4AulBCC Changer;
+			if(op->Changer)
+				Changer = MakeSetter(true);
+			// write byte code
+			AddBCC(op->Code, 0);
+			// writter setter
+			if(op->Changer)
+				AddBCC(Changer.bccType, Changer.Par.X);
+		}
 		break;
 	case ATT_BOPEN:
 		Shift();

src/script/C4AulScriptFunc.cpp

@@ -62,38 +62,12 @@ void C4AulScriptFunc::SetOverloaded(C4AulFunc * f)
 void C4AulScriptFunc::AddBCC(C4AulBCCType eType, intptr_t X, const char * SPos)
 {
 	// store chunk
-	C4AulBCC bcc;
-	bcc.bccType = eType;
-	bcc.Par.X = X;
-	Code.push_back(bcc);
+	Code.emplace_back(eType, X);
 	PosForCode.push_back(SPos);
-
-	switch (eType)
-	{
-	case AB_STRING: case AB_CALL: case AB_CALLFS: case AB_LOCALN: case AB_PROP:
-	/* case AB_LOCALN_SET/AB_PROP_SET: -- expected to already have a reference upon creation, see MakeSetter */
-		bcc.Par.s->IncRef();
-		break;
-	case AB_CARRAY:
-		bcc.Par.a->IncRef();
-		break;
-	default: break;
-	}
 }
 
 void C4AulScriptFunc::RemoveLastBCC()
 {
-	C4AulBCC *pBCC = &Code.back();
-	switch (pBCC->bccType)
-	{
-	case AB_STRING: case AB_CALL: case AB_CALLFS: case AB_LOCALN: case AB_LOCALN_SET: case AB_PROP: case AB_PROP_SET:
-		pBCC->Par.s->DecRef();
-		break;
-	case AB_CARRAY:
-		pBCC->Par.a->DecRef();
-		break;
-	default: break;
-	}
 	Code.pop_back();
 	PosForCode.pop_back();
 }

src/script/C4AulScriptFunc.h

@@ -93,18 +93,76 @@ enum C4AulBCCType
 };
 
 // byte code chunk
-struct C4AulBCC
+class C4AulBCC
 {
+public:
 	C4AulBCCType bccType; // chunk type
 	union
 	{
+		intptr_t X;
 		int32_t i;
 		C4String * s;
 		C4PropList * p;
 		C4ValueArray * a;
 		C4AulFunc * f;
-		intptr_t X;
 	} Par;    // extra info
+	C4AulBCC(): bccType(AB_ERR) { }
+	C4AulBCC(C4AulBCCType bccType, intptr_t X): bccType(bccType), Par{X}
+	{
+		IncRef();
+	}
+	C4AulBCC(const C4AulBCC & from): C4AulBCC(from.bccType, from.Par.X) { }
+	C4AulBCC & operator = (const C4AulBCC & from)
+	{
+		DecRef();
+		bccType = from.bccType;
+		Par = from.Par;
+		IncRef();
+		return *this;
+	}
+	C4AulBCC(C4AulBCC && from): bccType(from.bccType), Par(from.Par)
+	{
+		from.bccType = AB_ERR;
+	}
+	C4AulBCC & operator = (C4AulBCC && from)
+	{
+		DecRef();
+		bccType = from.bccType;
+		Par = from.Par;
+		from.bccType = AB_ERR;
+		return *this;
+	}
+	~C4AulBCC()
+	{
+		DecRef();
+	}
+private:
+	void IncRef()
+	{
+		switch (bccType)
+		{
+		case AB_STRING: case AB_CALL: case AB_CALLFS: case AB_LOCALN: case AB_LOCALN_SET: case AB_PROP: case AB_PROP_SET:
+			Par.s->IncRef();
+			break;
+		case AB_CARRAY:
+			Par.a->IncRef();
+			break;
+		default: break;
+		}
+	}
+	void DecRef()
+	{
+		switch (bccType)
+		{
+		case AB_STRING: case AB_CALL: case AB_CALLFS: case AB_LOCALN: case AB_LOCALN_SET: case AB_PROP: case AB_PROP_SET:
+			Par.s->DecRef();
+			break;
+		case AB_CARRAY:
+			Par.a->DecRef();
+			break;
+		default: break;
+		}
+	}
 };
 
 // script function class