- added readonly pointers. They need to be defined with 'readonly<classtype>'. These are significantly different from declaring a field readonly in that they do not disallow modification of the variable itself but what it points to. For the actor defaults this is necessary to prevent accidental modification. A readonly pointer is actually a different type than a regular pointer.

- fixed code generation for dynamic cast. It was missing the jump instruction after the compare.

src/dobjtype.cpp

@@ -1467,7 +1467,7 @@ END_POINTERS
 //==========================================================================
 
 PPointer::PPointer()
-: PBasicType(sizeof(void *), __alignof(void *)), PointedType(NULL)
+: PBasicType(sizeof(void *), __alignof(void *)), PointedType(NULL), IsConst(false)
 {
 	mDescriptiveName = "NullPointer";
 	SetOps();
@@ -1479,10 +1479,10 @@ PPointer::PPointer()
 //
 //==========================================================================
 
-PPointer::PPointer(PType *pointsat)
-: PBasicType(sizeof(void *), __alignof(void *)), PointedType(pointsat)
+PPointer::PPointer(PType *pointsat, bool isconst)
+: PBasicType(sizeof(void *), __alignof(void *)), PointedType(pointsat), IsConst(isconst)
 {
-	mDescriptiveName.Format("Pointer<%s>", pointsat->DescriptiveName());
+	mDescriptiveName.Format("Pointer<%s%s>", pointsat->DescriptiveName(), isconst? "readonly " : "");
 	SetOps();
 }
 
@@ -1570,14 +1570,14 @@ bool PPointer::ReadValue(FSerializer &ar, const char *key, void *addr) const
 //
 //==========================================================================
 
-PPointer *NewPointer(PType *type)
+PPointer *NewPointer(PType *type, bool isconst)
 {
 	size_t bucket;
-	PType *ptype = TypeTable.FindType(RUNTIME_CLASS(PPointer), (intptr_t)type, 0, &bucket);
+	PType *ptype = TypeTable.FindType(RUNTIME_CLASS(PPointer), (intptr_t)type, isconst ? 1 : 0, &bucket);
 	if (ptype == NULL)
 	{
 		ptype = new PPointer(type);
-		TypeTable.AddType(ptype, RUNTIME_CLASS(PPointer), (intptr_t)type, 0, bucket);
+		TypeTable.AddType(ptype, RUNTIME_CLASS(PPointer), (intptr_t)type, isconst ? 1 : 0, bucket);
 	}
 	return static_cast<PPointer *>(ptype);
 }

src/dobjtype.h

@@ -535,9 +535,10 @@ class PPointer : public PBasicType
 	HAS_OBJECT_POINTERS;
 public:
 	PPointer();
-	PPointer(PType *pointsat);
+	PPointer(PType *pointsat, bool isconst = false);
 
 	PType *PointedType;
+	bool IsConst;
 
 	virtual bool IsMatch(intptr_t id1, intptr_t id2) const;
 	virtual void GetTypeIDs(intptr_t &id1, intptr_t &id2) const;
@@ -877,7 +878,7 @@ PVector *NewVector(unsigned int size);
 PMap *NewMap(PType *keytype, PType *valuetype);
 PArray *NewArray(PType *type, unsigned int count);
 PDynArray *NewDynArray(PType *type);
-PPointer *NewPointer(PType *type);
+PPointer *NewPointer(PType *type, bool isconst = false);
 PClassPointer *NewClassPointer(PClass *restrict);
 PEnum *NewEnum(FName name, PTypeBase *outer);
 PStruct *NewStruct(FName name, PTypeBase *outer);

src/scripting/codegeneration/codegen.cpp

@@ -241,6 +241,7 @@ static bool AreCompatiblePointerTypes(PType *dest, PType *source)
 		auto fromtype = static_cast<PPointer *>(source);
 		auto totype = static_cast<PPointer *>(dest);
 		if (fromtype == nullptr) return true;
+		if (totype->IsConst && !fromtype->IsConst) return false;
 		if (fromtype == totype) return true;
 		if (fromtype->PointedType->IsKindOf(RUNTIME_CLASS(PClass)) && totype->PointedType->IsKindOf(RUNTIME_CLASS(PClass)))
 		{
@@ -3852,8 +3853,7 @@ ExpEmit FxTypeCheck::Emit(VMFunctionBuilder *build)
 FxDynamicCast::FxDynamicCast(PClass * cls, FxExpression *r)
 	: FxExpression(EFX_DynamicCast, r->ScriptPosition)
 {
-	expr = new FxTypeCast(r, NewPointer(RUNTIME_CLASS(DObject)), true, true);
-	ValueType = NewPointer(cls);
+	expr = r;
 	CastType = cls;
 }
 
@@ -3878,6 +3878,15 @@ FxExpression *FxDynamicCast::Resolve(FCompileContext& ctx)
 {
 	CHECKRESOLVED();
 	SAFE_RESOLVE(expr, ctx);
+	bool constflag = expr->ValueType->IsKindOf(RUNTIME_CLASS(PPointer)) && static_cast<PPointer *>(expr->ValueType)->IsConst;
+	expr = new FxTypeCast(expr, NewPointer(RUNTIME_CLASS(DObject), constflag), true, true);
+	expr = expr->Resolve(ctx);
+	if (expr == nullptr)
+	{
+		delete this;
+		return nullptr;
+	}
+	ValueType = NewPointer(CastType, constflag);
 	return this;
 }
 
@@ -3903,7 +3912,8 @@ ExpEmit FxDynamicCast::Emit(VMFunctionBuilder *build)
 
 	build->Emit(OP_CALL_K, build->GetConstantAddress(callfunc, ATAG_OBJECT), 2, 1);
 	build->Emit(OP_RESULT, 0, REGT_INT, check.RegNum);
-	auto patch = build->Emit(OP_EQ_K, 0, check.RegNum, build->GetConstantInt(0));
+	build->Emit(OP_EQ_K, 0, check.RegNum, build->GetConstantInt(0));
+	auto patch = build->Emit(OP_JMP, 0);
 	build->Emit(OP_LKP, out.RegNum, build->GetConstantAddress(nullptr, ATAG_OBJECT));
 	build->BackpatchToHere(patch);
 	return out;
@@ -5439,7 +5449,8 @@ FxStructMember::~FxStructMember()
 bool FxStructMember::RequestAddress(bool *writable)
 {
 	AddressRequested = true;
-	if (writable != nullptr) *writable = AddressWritable && !(membervar->Flags & VARF_ReadOnly);
+	if (writable != nullptr) *writable = (AddressWritable && !(membervar->Flags & VARF_ReadOnly) &&
+											(!classx->ValueType->IsKindOf(RUNTIME_CLASS(PPointer)) || !static_cast<PPointer*>(classx->ValueType)->IsConst));
 	return true;
 }
 

src/scripting/zscript/zcc-parse.lemon

@@ -668,6 +668,7 @@ type_name(X) ::= type_name1(A).
 	NEW_AST_NODE(BasicType, type, A);
 	type->Type = (EZCCBuiltinType)A.Int;
 	type->UserType = NULL;
+	type->isconst = false;
 	X = type;
 }
 type_name(X) ::= IDENTIFIER(A).			/* User-defined type (struct, enum, or class) */
@@ -676,14 +677,27 @@ type_name(X) ::= IDENTIFIER(A).			/* User-defined type (struct, enum, or class)
 	NEW_AST_NODE(Identifier, id, A);
 	type->Type = ZCC_UserType;
 	type->UserType = id;
+	type->isconst = false;
 	id->Id = A.Name();
 	X = type;
 }
+type_name(X) ::= READONLY LT IDENTIFIER(A) GT.
+{
+	NEW_AST_NODE(BasicType, type, A);
+	NEW_AST_NODE(Identifier, id, A);
+	type->Type = ZCC_UserType;
+	type->UserType = id;
+	type->isconst = true;
+	id->Id = A.Name();
+	X = type;
+}
+
 type_name(X) ::= DOT dottable_id(A).
 {
 	NEW_AST_NODE(BasicType, type, A);
 	type->Type = ZCC_UserType;
 	type->UserType = A;
+	type->isconst = false;
 	X = type;
 }
 

src/scripting/zscript/zcc_compile.cpp

@@ -1481,16 +1481,16 @@ PType *ZCCCompiler::ResolveUserType(ZCC_BasicType *type, PSymbolTable *symt)
 	if (sym == nullptr && symt != &GlobalSymbols) sym = GlobalSymbols.FindSymbolInTable(type->UserType->Id, table);
 	if (sym != nullptr && sym->IsKindOf(RUNTIME_CLASS(PSymbolType)))
 	{
-		auto type = static_cast<PSymbolType *>(sym)->Type;
-		if (type->IsKindOf(RUNTIME_CLASS(PEnum)))
+		auto ptype = static_cast<PSymbolType *>(sym)->Type;
+		if (ptype->IsKindOf(RUNTIME_CLASS(PEnum)))
 		{
 			return TypeSInt32;	// hack this to an integer until we can resolve the enum mess.
 		}
-		if (type->IsKindOf(RUNTIME_CLASS(PClass)))
+		if (ptype->IsKindOf(RUNTIME_CLASS(PClass)))
 		{
-			return NewPointer(type);
+			return NewPointer(ptype, type->isconst);
 		}
-		return type;
+		return ptype;
 	}
 	Error(type, "Unable to resolve %s as type.", FName(type->UserType->Id).GetChars());
 	return TypeError;

src/scripting/zscript/zcc_parser.h

@@ -310,6 +310,7 @@ struct ZCC_BasicType : ZCC_Type
 {
 	EZCCBuiltinType	Type;
 	ZCC_Identifier *UserType;
+	bool isconst;
 };
 
 struct ZCC_MapType : ZCC_Type

wadsrc/static/zscript/actor.txt

@@ -53,7 +53,7 @@ class Actor : Thinker native
 		return GetPointer(ptr_select1) == GetPointer(ptr_select2);
 	}
 
-	native static /*readonly*/ Actor GetDefaultByType(class<Actor> cls);
+	native static readonly<Actor> GetDefaultByType(class<Actor> cls);
 	native void SetDamage(int dmg);
 	native static bool isDehState(state st);
 	native void SetOrigin(vector3 newpos, bool moving);