Don't leak static proplists with cyclic references

If a local variable in a definition was set to a proplist inside the
Definition() callback, and that proplist contained cyclic references
then those references were leaked. Typically cyclic references for
script-created proplists are broken in
C4PropListScript::ClearScriptPropLists, however definition proplists
are changed to be static proplists in
C4PropList::FreezeAndMakeStaticRecursively.

To fix this, each script host maintains a list of proplists made static
by FreezeAndMakeStaticRecursively, and explicitly deletes all of these
proplists on Clear().

This leak also leads to an assertion failure inside
C4PropListScript::ClearScriptPropLists in debug mode, and can also be
observed by C4PropList::PropLists not being empty after game clear.

The definition in Objects.ocd/Helpers.ocd/UserAction.ocd constructs
cyclic proplists in its Definition() call. A simpler, more minimal way
to provoke the leak is the following (it provokes the leak but not the
assertion failure):

    local bla;

    func Definition(def)
    {
        bla = {};
        bla.test = { Name="Test222" , Options = { Name="Test333" } };
        bla.test.Options.Link = { Name="Test444", Blub=bla.test };
    }

src/script/C4Aul.cpp

@@ -86,6 +86,18 @@ void C4AulScriptEngine::Clear()
 	GlobalNamed.SetNameList(&GlobalNamedNames);
 	delete pGlobalEffects; pGlobalEffects=NULL;
 	UserFiles.clear();
+	// Delete all global proplists made static (breaks
+	// cyclic references).
+	for (C4Value& value: OwnedPropLists)
+	{
+		C4PropList* plist = value.getPropList();
+		if (plist)
+		{
+			if (plist->Delete()) delete plist;
+			else plist->Clear();
+		}
+	}
+	OwnedPropLists.clear();
 }
 
 void C4AulScriptEngine::RegisterGlobalConstant(const char *szName, const C4Value &rValue)

src/script/C4Aul.h

@@ -109,6 +109,7 @@ protected:
 	// all open user files
 	// user files aren't saved - they are just open temporary e.g. during game saving
 	std::list<C4AulUserFile> UserFiles;
+	std::vector<C4Value> OwnedPropLists;
 
 public:
 	int warnCnt, errCnt; // number of warnings/errors

src/script/C4AulLink.cpp

@@ -136,6 +136,9 @@ void C4ScriptHost::UnLink()
 		p->SetProperty(P_Prototype, C4VPropList(Engine->GetPropList()));
 	}
 
+	// Delete cyclic references of owned proplists
+	DeleteOwnedPropLists();
+
 	// includes will have to be re-resolved now
 	IncludesResolved = false;
 
@@ -179,8 +182,9 @@ void C4AulScriptEngine::Link(C4DefList *rDefs)
 
 		// Done modifying the proplists now
 		for (C4ScriptHost *s = Child0; s; s = s->Next)
-			s->GetPropList()->FreezeAndMakeStaticRecursively();
-		GetPropList()->FreezeAndMakeStaticRecursively();
+			s->GetPropList()->FreezeAndMakeStaticRecursively(&s->ownedPropLists);
+
+		GetPropList()->FreezeAndMakeStaticRecursively(&OwnedPropLists);
 	}
 	catch (C4AulError &err)
 	{

src/script/C4PropList.cpp

@@ -283,7 +283,7 @@ C4PropList::C4PropList(C4PropList * prototype):
 #endif
 }
 
-C4PropListStatic *C4PropList::FreezeAndMakeStaticRecursively(const C4PropListStatic *parent, C4String * key)
+C4PropListStatic *C4PropList::FreezeAndMakeStaticRecursively(std::vector<C4Value>* prop_lists, const C4PropListStatic *parent, C4String * key)
 {
 	Freeze();
 	// Already static?
@@ -301,6 +301,9 @@ C4PropListStatic *C4PropList::FreezeAndMakeStaticRecursively(const C4PropListSta
 			if (ref == &holder) ref = ref->NextRef;
 			ref->SetPropList(this_static);
 		}
+		// store reference
+		if (prop_lists)
+			prop_lists->push_back(C4VPropList(this_static));
 		// "this" should be deleted as holder goes out of scope
 	}
 	// Iterate over sorted list of elements to make static
@@ -318,7 +321,7 @@ C4PropListStatic *C4PropList::FreezeAndMakeStaticRecursively(const C4PropListSta
 			C4PropListStatic *child_static = child_proplist->IsStatic();
 			if (!child_static || (child_static->GetParent() == this_static && child_static->GetParentKeyName() == prop_name))
 			{
-				child_proplist->FreezeAndMakeStaticRecursively(this_static, prop_name);
+				child_proplist->FreezeAndMakeStaticRecursively(prop_lists, this_static, prop_name);
 			}
 		}
 	}

src/script/C4PropList.h

@@ -133,7 +133,8 @@ public:
 
 	// Freeze this and all proplist in properties and ensure they are static proplists
 	// If a proplist is not static, replace it with a static proplist and replace all instances
-	C4PropListStatic *FreezeAndMakeStaticRecursively(const C4PropListStatic *parent = nullptr, C4String * key = nullptr);
+	// Place references to all proplists made static in the given value array
+	C4PropListStatic *FreezeAndMakeStaticRecursively(std::vector<C4Value>* prop_lists, const C4PropListStatic *parent = nullptr, C4String * key = nullptr);
 
 	virtual void Denumerate(C4ValueNumbers *);
 	virtual ~C4PropList();

src/script/C4ScriptHost.cpp

@@ -53,6 +53,7 @@ void C4ScriptHost::Clear()
 	C4ComponentHost::Clear();
 	Script.Clear();
 	LocalValues.Clear();
+	DeleteOwnedPropLists();
 	SourceScripts.clear();
 	SourceScripts.push_back(this);
 	if (stringTable)
@@ -67,6 +68,23 @@ void C4ScriptHost::Clear()
 	State = ASS_NONE;
 }
 
+void C4ScriptHost::DeleteOwnedPropLists()
+{
+	// delete all static proplists associated to this script host.
+	// Note that just clearing the vector is not enough in case of
+	// cyclic references.
+	for (C4Value& value: ownedPropLists)
+	{
+		C4PropList* plist = value.getPropList();
+		if (plist)
+		{
+			if (plist->Delete()) delete plist;
+			else plist->Clear();
+		}
+	}
+	ownedPropLists.clear();
+}
+
 void C4ScriptHost::UnlinkOwnedFunctions()
 {
 	// Remove owned functions from their parents. This solves a problem

src/script/C4ScriptHost.h

@@ -53,8 +53,6 @@ public:
 	std::list<C4ScriptHost *> SourceScripts;
 	StdCopyStrBuf ScriptName; // script name
 
-	void UnlinkOwnedFunctions();
-
 protected:
 	C4ScriptHost();
 	void Unreg(); // remove from list
@@ -65,6 +63,9 @@ protected:
 	virtual bool Parse(); // parse preparsed script; return if successfull
 	virtual void UnLink(); // reset to unlinked state
 
+	void UnlinkOwnedFunctions();
+	void DeleteOwnedPropLists();
+
 	void Warn(const char *pMsg, ...) GNUC_FORMAT_ATTRIBUTE_O;
 
 	C4AulScriptEngine *Engine; //owning engine
@@ -89,6 +90,11 @@ protected:
 	// list of all functions generated from code in this script host
 	std::set<C4AulScriptFunc*> ownedFunctions;
 
+	// list of all static proplists that refer to this script host
+	// filled in at link time and used to delete all proplists
+	// in Clear() even in case of cyclic references.
+	std::vector<C4Value> ownedPropLists;
+
 	friend class C4AulParse;
 	friend class C4AulProfiler;
 	friend class C4AulScriptEngine;