- implemented VMCallWithDefaults and used it for all calls with variable arguments.

This isn't used for the 3 action function calls because it requires an array allocation which would be a bit too costly for something as frequently called as action functions.
They will need a different approach.

src/info.cpp

@@ -175,13 +175,13 @@ bool FState::CallAction(AActor *self, AActor *stateowner, FStateParamInfo *info,
 			
 			if (stateret == nullptr)
 			{
-				VMCallWithDefaults(ActionFunc, params, ActionFunc->ImplicitArgs, nullptr, 0);
+				VMCallAction(ActionFunc, params, ActionFunc->ImplicitArgs, nullptr, 0);
 			}
 			else
 			{
 				VMReturn ret;
 				ret.PointerAt((void **)stateret);
-				VMCallWithDefaults(ActionFunc, params, ActionFunc->ImplicitArgs, &ret, 1);
+				VMCallAction(ActionFunc, params, ActionFunc->ImplicitArgs, &ret, 1);
 			}
 		}
 		catch (CVMAbortException &err)

src/menu/menudef.cpp

@@ -477,7 +477,7 @@ static void ParseListMenuBody(FScanner &sc, DListMenuDescriptor *desc)
 					}
 					DMenuItemBase *item = (DMenuItemBase*)cls->CreateNew();
 					params[0] = item;
-					VMCallWithDefaults(func->Variants[0].Implementation, &params[0], params.Size(), nullptr, 0);
+					VMCallWithDefaults(func->Variants[0].Implementation, params, nullptr, 0);
 					desc->mItems.Push((DMenuItemBase*)item);
 
 					if (cls->IsDescendantOf("ListMenuItemSelectable"))
@@ -917,7 +917,7 @@ static void ParseOptionMenuBody(FScanner &sc, DOptionMenuDescriptor *desc)
 
 					DMenuItemBase *item = (DMenuItemBase*)cls->CreateNew();
 					params[0] = item;
-					VMCallWithDefaults(func->Variants[0].Implementation, &params[0], params.Size(), nullptr, 0);
+					VMCallWithDefaults(func->Variants[0].Implementation, params, nullptr, 0);
 					desc->mItems.Push((DMenuItemBase*)item);
 
 					success = true;

src/p_acs.cpp

@@ -5448,7 +5448,7 @@ static int ScriptCall(AActor *activator, unsigned argc, int32_t *args)
 		// The return value can be the same types as the parameter types, plus void
 		if (func->Proto->ReturnTypes.Size() == 0)
 		{
-			VMCallWithDefaults(func, &params[0], params.Size(), nullptr, 0);
+			VMCallWithDefaults(func, params, nullptr, 0);
 		}
 		else
 		{
@@ -5470,20 +5470,20 @@ static int ScriptCall(AActor *activator, unsigned argc, int32_t *args)
 			{
 				double d;
 				VMReturn ret(&d);
-				VMCallWithDefaults(func, &params[0], params.Size(), &ret, 1);
+				VMCallWithDefaults(func, params, &ret, 1);
 				retval = DoubleToACS(d);
 			}
 			else if (rettype == TypeString)
 			{
 				FString d;
 				VMReturn ret(&d);
-				VMCallWithDefaults(func, &params[0], params.Size(), &ret, 1);
+				VMCallWithDefaults(func, params, &ret, 1);
 				retval = GlobalACSStrings.AddString(d);
 			}
 			else
 			{
 				// All other return values can not be handled so ignore them.
-				VMCallWithDefaults(func, &params[0], params.Size(), nullptr, 0);
+				VMCallWithDefaults(func, params, nullptr, 0);
 			}
 		}
 	}

src/p_actionfunctions.cpp

@@ -170,7 +170,7 @@ bool AStateProvider::CallStateChain (AActor *actor, FState *state)
 			try
 			{
                 state->CheckCallerType(actor, this);
-				VMCallWithDefaults(state->ActionFunc, params, state->ActionFunc->ImplicitArgs, wantret, numret);
+				VMCallAction(state->ActionFunc, params, state->ActionFunc->ImplicitArgs, wantret, numret);
 			}
 			catch (CVMAbortException &err)
 			{

src/scripting/vm/vm.h

@@ -209,8 +209,6 @@ struct VMValue
 		const FString *sp;
 	};
 
-	// Unfortunately, FString cannot be used directly.
-	// Fortunately, it is relatively simple.
 	const FString &s() const { return *sp; }
 
 	VMValue()
@@ -376,8 +374,9 @@ private:
 };
 
 int VMCall(VMFunction *func, VMValue *params, int numparams, VMReturn *results, int numresults/*, VMException **trap = NULL*/);
+int VMCallWithDefaults(VMFunction *func, TArray<VMValue> &params, VMReturn *results, int numresults/*, VMException **trap = NULL*/);
 
-inline int VMCallWithDefaults(VMFunction *func, VMValue *params, int numparams, VMReturn *results, int numresults/*, VMException **trap = NULL*/)
+inline int VMCallAction(VMFunction *func, VMValue *params, int numparams, VMReturn *results, int numresults/*, VMException **trap = NULL*/)
 {
 	return VMCall(func, params, numparams, results, numresults);
 }

src/scripting/vm/vmframe.cpp

@@ -577,6 +577,18 @@ int VMCall(VMFunction *func, VMValue *params, int numparams, VMReturn *results,
 #endif
 }
 
+int VMCallWithDefaults(VMFunction *func, TArray<VMValue> &params, VMReturn *results, int numresults/*, VMException **trap = NULL*/)
+{
+	if (func->DefaultArgs.Size() > params.Size())
+	{
+		auto oldp = params.Size();
+		params.Resize(func->DefaultArgs.Size());
+		memcpy(&params[oldp], &func->DefaultArgs[oldp], (params.Size() - oldp) * sizeof(VMValue));
+	}
+	return VMCall(func, params.Data(), params.Size(), results, numresults);
+}
+
+
 // Exception stuff for the VM is intentionally placed there, because having this in vmexec.cpp would subject it to inlining
 // which we do not want because it increases the local stack requirements of Exec which are already too high.
 FString CVMAbortException::stacktrace;