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I'm working on some simple script language and I need a help in understanding how garbage collector works. As far as I understand it, garbage collector has two things:

  1. Object pool - contains all allocated objects, can be represented as simple array. When VM creates an object (Number, String and etc) it creates appropriate instance and pushes it into the object pool:

    // init object pool
var objectPool = [];
// create new Number
var numberObj = new Number(123);
// push numberObj into objectPool
objectPool.push(numberObj);
// create new String
var stringObj = new String("foo");
// push stringObj into objectPool
objectPool.push(stringObj);

  2. Frame (not sure if it's right term) - contains references to the objects in objectPool. When we create a variable and assign a value to it, VM creates entry in the Frame. When we need to get variable value we look it in the frame. Frame can be represented as hash map:

    // init frame
var frame = {};
// create new String
var stringObj = new String("bar");
// push stringObj into objectPool
objectPool.push(stringObj);
// write stringObj into the frame
frame["foo"] = stringObj;

Garbage collection (at least mark & sweep implementation), contains two steps:

  1. Mark: walk through the objects that is contained in frame and mark them:

    for (var varName in frame)
  frame[varName].marked = true;

  2. Sweep: walk through the objects that is contained in objectPool and remove (free) all unmarked ones:

    for (var c = 0; c < objectPool.length; c++) {
  if (!objectPool[c].marked) {
    free(objectPool[c]);
    remove(objectPool[c]);
  }
}

Am I missing anything? Is this all looks correct?

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