How to catch stack overflow?

[alexcrichton]

Occasionally from time to time you'll accidentally write a deeply recursive function which blows the stack. Ideally this is caught and identified immediately, but sometimes a stack overflow can cause crazy corruption throughout the system and be otherwise very hard to debug.

Currently there's no mechanism for catching a stack overflow with wasm, and a stack overflow ends up corrupting the globals section most likely (oh dear!).

[Diggsey]

I think we might have run into this with stdweb... https://github.com/benkonz/texture_issue/pull/1#issuecomment-382498172

[sendilkumarn]

yes it would be awesome to know how to debug this thing

[CryZe]

Maybe Rust could have a special compiler flag that introduces additional stack overflow checks and panics if it detects one.

[pepyakin]

@CryZe Yeah, that's definitely a good idea, even if it would be opt-out.

[fitzgen]

I think we should change the memory layout constructed by lld, as described in https://github.com/rust-lang-nursery/rust-wasm/issues/81#issuecomment-382880848

[alexcrichton]

Yeah I do think that it's probably best to just change the default layout at this time. One unfortunate part is that it's still not easy to diagnose (a "segfault" and stack overflow look exactly the same). I think the only way we could handle that currently, though, would be to add a condition on all function calls that checks the current stack pointer (which may have a perf hit)

[alexcrichton]

I believe this was covered by --stack-first in LLD on https://github.com/rust-lang-nursery/rust-wasm/issues/81

[pjtatlow]

Hey guys! I've been struggling with trying to detect (in JS) when a stack overflow occurs in my rust code (wasm). I see this issue has been closed for a while, but I'm not sure how to fix this myself. I'm hoping to be able to know when this happens, as well as when Exceptions like this happen:

Uncaught (in promise) RuntimeError: memory access out of bounds

Is this possible or no? Currently the promise that is returned from WASM just never resolves, which leaves the user spinning forever. Any ideas?

[alecmocatta]

@pjtatlow window.addEventListener('unhandledrejection', (event) => { ... }) works to catch such exceptions for me in Firefox and Safari, though it doesn't work in Chrome or Edge. See rustwasm/wasm-bindgen#2392 for more details.