From 9aff83cfdc117610e5203f74f7641808927256cf Mon Sep 17 00:00:00 2001
From: "alexey.lysiuk" <alexey.lysiuk@gmail.com>
Date: Sun, 20 Oct 2019 12:59:20 +0300
Subject: [PATCH] - implicitly clear local dynamic arrays

https://forum.zdoom.org/viewtopic.php?t=62710
---
 src/scripting/backend/codegen.cpp | 38 +++++++++++++++++++------------
 src/scripting/backend/codegen.h   |  7 +++++-
 2 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/src/scripting/backend/codegen.cpp b/src/scripting/backend/codegen.cpp
index 004764b3d..360b7c4f3 100644
--- a/src/scripting/backend/codegen.cpp
+++ b/src/scripting/backend/codegen.cpp
@@ -11276,6 +11276,7 @@ FxLocalVariableDeclaration::FxLocalVariableDeclaration(PType *type, FName name,
 	Name = name;
 	RegCount = type == TypeVector2 ? 2 : type == TypeVector3 ? 3 : 1;
 	Init = initval;
+	clearExpr = nullptr;
 }
 
 FxLocalVariableDeclaration::~FxLocalVariableDeclaration()
@@ -11286,6 +11287,15 @@ FxLocalVariableDeclaration::~FxLocalVariableDeclaration()
 FxExpression *FxLocalVariableDeclaration::Resolve(FCompileContext &ctx)
 {
 	CHECKRESOLVED();
+
+	if (IsDynamicArray())
+	{
+		auto stackVar = new FxStackVariable(ValueType, StackOffset, ScriptPosition);
+		FArgumentList argsList;
+		clearExpr = new FxMemberFunctionCall(stackVar, "Clear", argsList, ScriptPosition);
+		SAFE_RESOLVE(clearExpr, ctx);
+	}
+
 	if (ctx.Block == nullptr)
 	{
 		ScriptPosition.Message(MSG_ERROR, "Variable declaration outside compound statement");
@@ -11480,6 +11490,10 @@ ExpEmit FxLocalVariableDeclaration::Emit(VMFunctionBuilder *build)
 			}
 			if (pstr->mDestructor != nullptr) build->ConstructedStructs.Push(this);
 		}
+		else if (ValueType->isDynArray())
+		{
+			ClearDynamicArray(build);
+		}
 	}
 	return ExpEmit();
 }
@@ -11511,6 +11525,11 @@ void FxLocalVariableDeclaration::Release(VMFunctionBuilder *build)
 	// For that all local stack variables need to live for the entire execution of a function.
 }
 
+void FxLocalVariableDeclaration::ClearDynamicArray(VMFunctionBuilder *build)
+{
+	assert(clearExpr != nullptr);
+	clearExpr->Emit(build);
+}
 
 FxStaticArray::FxStaticArray(PType *type, FName name, FArgumentList &args, const FScriptPosition &pos)
 	: FxLocalVariableDeclaration(NewArray(type, args.Size()), name, nullptr, VARF_Static|VARF_ReadOnly, pos)
@@ -11595,7 +11614,6 @@ FxLocalArrayDeclaration::FxLocalArrayDeclaration(PType *type, FName name, FArgum
 {
 	ExprType = EFX_LocalArrayDeclaration;
 	values = std::move(args);
-	clearExpr = nullptr;
 }
 
 FxExpression *FxLocalArrayDeclaration::Resolve(FCompileContext &ctx)
@@ -11611,16 +11629,6 @@ FxExpression *FxLocalArrayDeclaration::Resolve(FCompileContext &ctx)
 	auto elementType = (static_cast<PArray *> (ValueType))->ElementType;
 	auto elementCount = (static_cast<PArray *> (ValueType))->ElementCount;
 
-	// We HAVE to clear dynamic arrays before initializing them
-	if (IsDynamicArray())
-	{
-		FArgumentList argsList;
-		argsList.Clear();
-
-		clearExpr = new FxMemberFunctionCall(stackVar, "Clear", argsList, (const FScriptPosition) ScriptPosition);
-		SAFE_RESOLVE(clearExpr, ctx);
-	}
-
 	if (values.Size() > elementCount)
 	{
 		ScriptPosition.Message(MSG_ERROR, "Initializer contains more elements than the array can contain");
@@ -11677,9 +11685,11 @@ ExpEmit FxLocalArrayDeclaration::Emit(VMFunctionBuilder *build)
 {
 	assert(!(VarFlags & VARF_Out));	// 'out' variables should never be initialized, they can only exist as function parameters.
 
-	if (IsDynamicArray() && clearExpr != nullptr)
+	const bool isDynamicArray = IsDynamicArray();
+
+	if (isDynamicArray)
 	{
-		clearExpr->Emit(build);
+		ClearDynamicArray(build);
 	}
 
 	auto elementSizeConst = build->GetConstantInt(static_cast<PArray *>(ValueType)->ElementSize);
@@ -11690,7 +11700,7 @@ ExpEmit FxLocalArrayDeclaration::Emit(VMFunctionBuilder *build)
 	{
 		ExpEmit emitval = v->Emit(build);
 
-		if (IsDynamicArray())
+		if (isDynamicArray)
 		{
 			continue;
 		}
diff --git a/src/scripting/backend/codegen.h b/src/scripting/backend/codegen.h
index aa05c7d06..26f2011b2 100644
--- a/src/scripting/backend/codegen.h
+++ b/src/scripting/backend/codegen.h
@@ -2131,6 +2131,12 @@ class FxLocalVariableDeclaration : public FxExpression
 	FxExpression *Init;
 	int VarFlags;
 	int RegCount;
+
+protected:
+	FxExpression *clearExpr;
+
+	void ClearDynamicArray(VMFunctionBuilder *build);
+
 public:
 	int StackOffset = -1;
 	int RegNum = -1;
@@ -2194,7 +2200,6 @@ class FxLocalArrayDeclaration : public FxLocalVariableDeclaration
 {
 	PType *ElementType;
 	FArgumentList values;
-	FxExpression *clearExpr;
 
 public: