Unable to Obtain Current Stack Trace without a Trap

[jtenner]

Hey! I am trying to obtain the current stack trace without invoking a panic, inside a linked function.

// this is awesome!
let backtrace = Backtrace::new();

I can access the stack frames using Backtrace::new() but I can't really do anything with it because all the functions that translate these into function names and strings are pub(crate) and internal to wasmtime.

Is there perhaps a safe way to obtain the current stack trace without calling a wasm function that executes an unreachable() instruction?

[alexcrichton]

While not currently possible now I opened #5341 to expose a method for doing this.

[jtenner]

@alexcrichton it looks like the WasmBacktrace::new() function is private and not exposed. Can I get some help with this?

[alexcrichton]

Ah sorry I forgot to update the PR title, the constructor is WasmBacktrace::capture now.

[jtenner]

error[E0599]: no function or associated item named `capture` found for struct `WasmBacktrace` in the current scope
   --> crates\lunatic-process-api\src\lib.rs:805:36
    |
805 |     let backtrace = WasmBacktrace::capture();
    |                                    ^^^^^^^ function or associated item not found in `WasmBacktrace`

[alexcrichton]

Are you using main or the release-4.0.0 branch? This feature isn't present in any crates.io-based release of Wasmtime yet.

[jtenner]

@alexcrichton I'm downstream using lunatic on version 3.0.1 so that explains why the feature wasn't present. My mistake.