fitzgen (he/him) (Jul 20 2026 at 15:52): fitzgen (he/him) (Jul 20 2026 at 15:52):https://bytecodealliance.org/articles/wasmtime-gc
The Wasm GC and exceptions proposals are both enabled by default in today’s Wasmtime 47 release! We are excited to help bring more languages to WebAssembly and everywhere that Wasmtime runs. Getting to this point involved large Wasmtime changes and represents the culmination of years of engineering effort.
Zalim Bashorov (Kotlin_, JetBrains) (Jul 21 2026 at 22:22):Congrats, folks! :tada:
fitzgen (he/him) (Jul 21 2026 at 22:57):Zalim Bashorov (Kotlin_, JetBrains) said:
Congrats, folks! :tada:
Thanks! And thanks for all the bug reports and tire kicking!
kripken (Jul 27 2026 at 17:23):Great!
I have a question about this part:
We reuse WebAssembly linear memories under the covers to implement and sandbox the GC heap [..] this lets us use virtual-memory guard pages to elide explicit bounds checks
I understand this adds sandboxing, but which "explicit bounds checks" is it eliding?
(AFAIK similar sandboxing techniques like WebKit's gigacage and the V8 sandbox do not use bounds checks by design. And I assume this does not mean removing the explicit bounds checks on array accesses?)
fitzgen (he/him) (Jul 27 2026 at 20:01):kripken said:
I understand this adds sandboxing, but which "explicit bounds checks" is it eliding?
ah yeah that wording is perhaps a bit ambiguous. it is referring to the explicit bounds checks that we'd otherwise have to insert to sandbox the gc heap if we weren't using guard pages and virtual memory tricks
fitzgen (he/him) (Jul 27 2026 at 20:01):not any bounds checks required by the spec, for example
kripken (Jul 27 2026 at 20:33):I see, thanks!
Last updated: Jul 29 2026 at 05:03 UTC