Gc-arena Alternatives

gc-arena reviews and mentions

• I built a garbage collector for a language that doesn't need one
  3 projects | news.ycombinator.com | 14 Aug 2023

  I'm going to point out one potential footgun with your library: circularly-linked Drops.

  If you have values A and B, both instances of T that implement Drop and hold a Gc to one another, then either A sees a dropped B or B sees a dropped A, and you get UB. Technically this isn't a problem because you already marked it as an unsafe trait, but your documentation should also mention this problem.

  You have a safe derive macro for Collectable, however, so it needs to reject Drop. This is possible with some weird macro magic[0].

  For those wondering, while Python doesn't have UB, it used to enforce the same rules until PEP 442[1]. Circularly linked garbage that implemented __del__ would instead get stored in sys.gc.garbage and you'd have to go in there and break references on __del__ types. However, native code objects will actually still trigger this behavior[2] presumably to avoid UB.

  I have no clue if Java finalizers need to worry about this.

  [0] In Ruffle we use gc_arena as our garbage collector. It enforces no_drop in it's Collect derive macro. See: https://github.com/kyren/gc-arena/blob/master/src/gc-arena-d...

  Actually, I lied: no_drop is one of two safe constraints you can use Collect with. The alternative is require_static, which only works because gc_arena treats the entire GC heap as a data structure that is owned and has a lifetime that all Gc pointers borrow. This doesn't work for dumpster, though, so ignore it.

  [1] https://peps.python.org/pep-0442/

  [2] https://docs.python.org/3/library/gc.html#gc.garbage

• Make a LISP in Rust tutorial starting tomorrow.
  4 projects | /r/learnrust | 21 Dec 2022

  I foresee some potential problems with this approach. I would recommend trying to find an arena-based GC crate that you could use. gc-arena looks promising, although I haven't tried it — it seems to be built for your specific use case.

• Implementing a safe garbage collector in Rust
  2 projects | /r/rust | 12 Apr 2022

  gc-arena uses closures to create "mutation sessions" where you are allowed to mutate the heap (see example).

• GhostCell: Separating Permissions from Data in Rust
  2 projects | /r/rust | 31 Mar 2021

  One example of the second approach is the gc-arena library- see the implementation of the make_arena! macro.

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