Catch panic in SmartModule

[galibey]

When the WASM compiled code in SmartModule panics the execution aborts and wasmtime engine returns wasm trap: wasm unreachable instruction executed. We need to discover the solution to handle the panic with proper error reporting to the user.

Related #2286

[sehz]

How about this? https://crates.io/crates/console_error_panic_hook

[galibey]

How about this? https://crates.io/crates/console_error_panic_hook

This is just a panic hook that forwards a message to JS native function. In theory, we could use a hook to store a message to some static memory and then use it to report an error but it's quite a hacky and the hook can conflict with the user's hook.

What we can do is to analyze wasm backtraces returned from func call in wasmtime and lookup for the function __rust_start_panic. If one is found, we report that the user's code panicked without providing any reasons or code positions.

[galibey]

Created an issue in wasmtime https://github.com/bytecodealliance/wasmtime/issues/4054

[galibey]

For WASI targeted modules we can capture stderr and in case of Trap returned from WebAssembly function invocation we can report the output to the user as an error. Example:

...
let shared_stderr = Arc::new(RwLock::new(Cursor::new(vec![])));
let wasi = WasiCtxBuilder::new()
        .stderr(Box::new(WritePipe::from_shared(shared_stderr.clone())))
        .build();
...
let result = instance.get_typed_func::<(), (), _>(&mut store, "filter");
///if result = Err(trap)
let cursor = shared_stderr.read().unwrap();
let error_message = String::from_utf8_lossy(cursor.get_ref());

If the module has no WASI, we can detect if Trap with UnreachableCodeReached and add the message that most probably the code panicked and advise to re-build the code to WASI to be able to debug the issue.

[github-actions[bot]]

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