how is that different from compiling against a traditional CPU which also doesn't have a built in GC? i mean those programs that need a GC already have one. so what is the benefit of including one on the "CPU"?
The fact that a minimum size go program is a few megabytes in size is acceptable in most places in 2025. If it was shipped over the wire for every run time instead of a single install time download, that would be a different story.
Garbage collection is a small part of the go run time, but it's not insignificant.
Skimming this issue, it seems like they weren't expecting to be able to use this GC. I know C# couldn't either, at least based on an earlier state of the proposal.
this thread confirms my suspicions. some languages may benefit from a built in GC, but those languages probably use a generic GC to begin with. wheras any language that has a highly optimized GC for their own needs won't be able to use this one.
The "CPU" in every browser already has one. This lets garbage-collected languages use that one. That's an enormous savings in code size and development effort.
i don't see the reduced development effort, after all, unless the language is only running on webassembly i still need to implement my own GC for other CPUs.
so most GC-languages being ported to webassembly already have a GC, so what is the benefit of using a provided GC then?
on the other hand i see GC as a feature that could become part of any modern CPU. then the benefit would be large, as any language could use it and wouldn't have to implement their own at all anymore.
Aside from code size the primary benefit on the Web is that the GC provided to wasm is the same one for the outer JavaScript engine, so an object from wasm can stay alive get collected based on whether JS keeps references to it. So it’s not really about providing a GC for a single wasm module (program), its about participating in one cooperatively with other programs.
Writing a GC that performs well often involves making decisions that are tightly coupled to the processor architecture and operating system as well as the language implementation's memory representations for objects. Using a GC that is already present can solve that problem.
> i don't see the reduced development effort, after all, unless the language is only running on webassembly i still need to implement my own GC for other CPUs.
I'd think porting an existing GC to WASM is more effort than using WASM's GC for a GC'd language?
i don't think so. first of all, you don't rewrite your code for every CPU but you just adapt some specific things. most code is just compiled for the new architecture and runs. second, those languages that are already running on wasm have already done the work. so at best new languages who haven't been ported yet will get any benefit from a reduced porting effort.
WebAssembly programs can't directly read their own stack because of how it's designed, meaning that scanning for live objects within WASM is inefficient as you have to keep a separate stack in software for GC
Garbage collection is a small part of the go run time, but it's not insignificant.