Could anyone point me to a good source on how to implement garbage collection? I am making a lisp-like interpreted language. It currently uses reference counting, but of course that fails at freeing circularly dependent objects.
I’ve been reading of mark and sweep, tricolor marking, moving and nonmoving, incremental and stop-the-world, but… I don’t know what the best way to keep the objects neatly separated into sets while keeping per-object memory overhead at a minimum, or how to do things incrementally.
I’ve read some languages with reference counting use circular reference detection, which I could use. I am aware I could use freely available collectors like Boehm, but I would like to learn how to do it myself.
I would appreciate any online material with some sort of tutorial or help for people with no experience on the topic like myself.
As suggested by delnan, I started with a very naïve stop-the-world tri-color mark and sweep algorithm. I managed to keep the objects in the sets by making them linked-list nodes, but it does add a lot of data to each object (the virtual pointer, two pointers to nodes, one enum to hold the color). It works perfectly, no memory lost on valgrind 🙂 From here I might try to add a free list for recycling, or some sort of thing that detects when it is convenient to stop the world, or an incremental approach, or a special allocator to avoid fragmentation, or something else. If you can point me where to find info or advice (I don’t know whether you can comment on an answered question) on how to do these things or what to do, I’d be very thankful. I’ll be checking Lua’s GC in the meantime.