Baby's Second Garbage Collector

(matheusmoreira.com)

33 points | by matheusmoreira 3 days ago ago

6 comments

  • DevelopingElk 6 minutes ago

    Good? Bad? Doesn't matter as long as you had fun.

    Have you tested this GCs performance? Sometimes a baby GC can be fast enough.

  • frutiger 4 hours ago

    I wanted to read this but I couldn’t because of all the allusions in the article that distracted me from the points the author was trying to make.

    • starkeeper 29 minutes ago

      Yeah it totally grossed me out too, it's quite twisted. Author has serious issues.

    • allthetime 4 hours ago

      On mobile all the text is about 3 times bigger than it needs to be as well making for an obnoxious amount of scrolling. Unreadable code examples.

      • matheusmoreira 3 hours ago

        Thanks for the feedback. That's due to a viewport configuration meta tag which I added recently in an attempt to make it more responsive in portrait mode. I just reverted it. Should work just like on desktop now.

  • mananaysiempre 3 hours ago

    TL;DR: Conservative collector. Not where I would have taken things, but valid.

    Re forcing a register spill: assuming the GC is invoked via an ABI-compliant function call, you don’t actually need to save all the scalar registers manually, only the callee-save ones (as setjmp does). Alternatively, you can make the compiler do the spilling by inserting a function preserving no registers into the call chain—this is spelled __attribute__((preserve_none)) in sufficiently new Clang or GCC, but you can also accomplish this kind of thing on Watcom with #pragma aux, for example.

    Re obtaining the top and bottom of the stack: in addition to __builtin_frame_address, there’s also the age-old option of declaring a local and looking at its address, as long as strict aliasing doesn’t bite you. And if you know you’re running on Linux or something sufficiently compatible (as seen from the reference to auxv), you can treat argv as the bottom of the stack for the main thread, as the startup stack on Linux is (IIRC) argv, then the argument strings, then the environment, then the auxiliary vector.