You probably don’t like memory leaks. I don’t. But, if you have one object that needs to pass between two languages — C++ and JavaScript — each of which may keep that object indefinitely, it can become tricky to make sure that any given object is destroyed, and that it is destroyed at the right time.

There are two things that can happen: an object can be deleted two soon, while it is still being used elsewhere — causing some particularly delicious crashes — or, an object can be deleted too late (or not at all), causing memory leaks.

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So, a problem arose.

I wanted to account for two possibilities in the Script Engine: Passing existing objects from C++ to JavaScript, and creating new C++ objects from JavaScript. The act of passing a native object into scripting languages is usually referred to as wrapping (although, at one point inside the engine, I actually refer to a part of the process as unwrapping).

The code I would like to be able to use is:

//create a point
Point *point = new Point(.42, 42);
 
//pass it to some JavaScript function
myJavaScriptFunction->Call(pointWrap(point), 0, NULL);

//create a Point
var point = new Point();
 
//set its X value
point.x = 4.2;
 
//call some C++ function using it
myCPPFunction(point);

So how did I manage this in the engine? Well, as I am prone do, I overcomplicated it.

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