Fix "t->c->value.argSize == func->parmTotal" Assertion in Scripts, #303

If a "class" (object) in a Script has multiple member function
prototypes, and one function implementation later calls another before
that is implemented, there was an assertion when the script was parsed
(at map start), because the size of function arguments at the call-site
didn't match what the function expected - because the function hadn't
calculated that size yet, that only happened once its own
implementation was parsed.
Now it's calculated (and stored) when the prototype/declaration is
parsed to prevent this issue, which seems to be kinda common with Mods,
esp. Script-only mods, as the release game DLLs had Assertions disabled.

d3xp/script/Script_Compiler.cpp

@@ -2144,15 +2144,18 @@ void idCompiler::ParseFunctionDef( idTypeDef *returnType, const char *name ) {
 		}
 	}
 
-	// check if this is a prototype or declaration
+	// DG: make sure parmSize gets calculated when parsing prototype (not just when parsing
-	if ( !CheckToken( "{" ) ) {
+	//     implementation) so calling this function/method before implementation has been parsed
-		// it's just a prototype, so get the ; and move on
+	//     works without getting Assertions in IdInterpreter::Execute() and ::LeaveFunction()
-		ExpectToken( ";" );
+	//     ("st->c->value.argSize == func->parmTotal", "localstackUsed == localstackBase", see #303)
-		return;
-	}
 
 	// calculate stack space used by parms
 	numParms = type->NumParameters();
+	if( numParms != func->parmSize.Num() ) { // DG: make sure not to do this twice
+
+		// if it hasn't been parsed yet, parmSize.Num() should be 0..
+		assert( func->parmSize.Num() == 0 && "function had different number of arguments before?!" );
+
 		func->parmSize.SetNum( numParms );
 		for( i = 0; i < numParms; i++ ) {
 			parmType = type->GetParmType( i );
@@ -2171,6 +2174,16 @@ void idCompiler::ParseFunctionDef( idTypeDef *returnType, const char *name ) {
 			}
 			gameLocal.program.AllocDef( type->GetParmType( i ), type->GetParmName( i ), def, false );
 		}
+	}
+
+	// DG: moved this down here so parmSize also gets calculated when parsing prototype
+	// check if this is a prototype or declaration
+	if ( !CheckToken( "{" ) ) {
+		// it's just a prototype, so get the ; and move on
+		ExpectToken( ";" );
+		return;
+	}
+	// DG end
 
 	oldscope = scope;
 	scope = def;

game/script/Script_Compiler.cpp

@@ -2144,15 +2144,18 @@ void idCompiler::ParseFunctionDef( idTypeDef *returnType, const char *name ) {
 		}
 	}
 
-	// check if this is a prototype or declaration
+	// DG: make sure parmSize gets calculated when parsing prototype (not just when parsing
-	if ( !CheckToken( "{" ) ) {
+	//     implementation) so calling this function/method before implementation has been parsed
-		// it's just a prototype, so get the ; and move on
+	//     works without getting Assertions in IdInterpreter::Execute() and ::LeaveFunction()
-		ExpectToken( ";" );
+	//     ("st->c->value.argSize == func->parmTotal", "localstackUsed == localstackBase", see #303)
-		return;
-	}
 
 	// calculate stack space used by parms
 	numParms = type->NumParameters();
+	if( numParms != func->parmSize.Num() ) { // DG: make sure not to do this twice
+
+		// if it hasn't been parsed yet, parmSize.Num() should be 0..
+		assert( func->parmSize.Num() == 0 && "function had different number of arguments before?!" );
+
 		func->parmSize.SetNum( numParms );
 		for( i = 0; i < numParms; i++ ) {
 			parmType = type->GetParmType( i );
@@ -2171,6 +2174,16 @@ void idCompiler::ParseFunctionDef( idTypeDef *returnType, const char *name ) {
 			}
 			gameLocal.program.AllocDef( type->GetParmType( i ), type->GetParmName( i ), def, false );
 		}
+	}
+
+	// DG: moved this down here so parmSize also gets calculated when parsing prototype
+	// check if this is a prototype or declaration
+	if ( !CheckToken( "{" ) ) {
+		// it's just a prototype, so get the ; and move on
+		ExpectToken( ";" );
+		return;
+	}
+	// DG end
 
 	oldscope = scope;
 	scope = def;