Native Code and Monkey's Garbage Collection
Monkey Archive Forums/Monkey Tutorials/Native Code and Monkey's Garbage Collection
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| This is a loose set of notes, and is current for Monkey V66 (and 67). Some of these notes may be incorrect, use at your own risk. --------------- Preface: Most modern languages tend to have garbage collection (GC) built-in, so this is really only needed in C++. Also be aware that this GC does not work with multiple threads at this time. Here's how the GC works: It's a mark-sweep algorithm, called every cycle (about once a frame). Say you have an object, and you want monkey to manage the object's GC, then you will need to extend the object's class with Monkey's native built-in Object Class (ie: class MyClass : public Object {} ....etc). Any data types within the class are managed, as are classes using "new" (that extend Object), but not dynamically allocated memory (malloc). wxWidgets example:
class wxMonkeyTimer : public Object, public wxTimer {
public:
wxMonkeyTimer() {};
~wxMonkeyTimer() {};
void mark() {
Object::mark();
};
};
By extending from the base monkey class "Object", the class's "new" is overloaded and added to the GC's main mark_roots function, which is called once per update cycle. You really only need "Object::mark()" if you want to extend that class with another one, in monkey or natively, and have it managed as well. I also discovered order is important for extending the base Object, it should be first before other extensions. (c++ experts probably already know this) If you are allocating your own memory in your class, then you need to use gc_mark or gc_mark_q. I *think* the difference between the two is that gc_mark is managed memory collection, gc_mark_q is unmanaged, you collect it in your own class. ( i need to test and confirm this. ) You will also need to gc_assign() your managed variables upon creation since you are not using the constructor. |
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| Good question was brought up: do I need to gc_mark pointers? No, the class treats pointers as an address type so it is kept locally in the class, which is managed. I think it's ULONG on 64-bit (correct me if im wrong). So if the pointer points to a memory block, monkey's GC won't see the memory, only the pointer. Therefore, your class will need to malloc() and free() it manually before releasing the pointer. |
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| Good question was brought up: do I need to gc_mark pointers? No, the class treats pointers as an address type so it is kept locally in the class, which is managed. I think it's ULONG on 64-bit (correct me if im wrong). So if the pointer points to a memory block, monkey's GC won't see the memory, only the pointer. Therefore, your class will need to malloc() and free() it manually before releasing the pointer. |
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| Monkey's Garbage Collection info (V71) has been updated here: https://github.com/blitz-research/monkey/wiki/Garbage-collection |
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