✔ Variable not available · wasmtime

Got same issue. Seems to be a wasmtime regression. Will try with other engines to attempt to identify more precisely than hunch.

Steve Williams (Oct 25 2025 at 14:10):

Thought it was an lldb regression or side effect from method I've used to re-activate wasm breakpoints, however on further reading, seems wasmtime has had this issue in the past & it's potentially returned.

LLDB: Breakpoints regressed - Web Assembly invoked from WASM C-API in a dynamic library (fix included) · Issue #163799 · llvm/llvm-project

What happened : LLDB breakpoints stopped working. Specific use case example here : https://advance-software.com/develop/#tutorial Our app invokes Web Asssembly C-API from a plugin (DLL on Windows) ...

Till Schneidereit (Oct 25 2025 at 14:11):

These are separate issues: one is about breakpoints not working, the other about variable inspection

Steve Williams (Oct 25 2025 at 14:13):

the variable inspection one is the more important. bcoz if that's a genuine regression in wasmtime, it means the breakpoint fix I have isn't so far off correct.

Till Schneidereit (Oct 25 2025 at 14:15):

All I'm saying is that it'd be good to keep them separate instead of claiming they're the same issue

Steve Williams (Oct 25 2025 at 14:16):

well, the variables not resolving issue is the same - perhaps different causes, perhaps not. this post interesting as it shows the problem without, it seems any changes to lldb.

Till Schneidereit (Oct 25 2025 at 14:18):

it is absolutely not the same issue: the symptoms are completely different, the impact on usability is different depending on requirements, and the underlying causes are very different as well. Additionally, your issue is limited to your specific way of embedding Wasmtime, wheres this is affecting the wasmtime CLI. I get that both are problems for you, but that doesn't make them the same issue.

Steve Williams (Oct 25 2025 at 14:19):

we're guessing. next step, needs a simple wasm in c or rust demonstrating the problem - I'll see if I can generate a simple repro. anyone else who gets one, first, that'd help.

Till Schneidereit (Oct 25 2025 at 14:20):

@Scott Waye we unfortunately have some bugs in our implementation of transforming Wasm DWARF to native as part of compilation, as reported in a number of issues. There's some work on improving that, but the bigger effort for guest debugging is in completely changing the approach. There's very active work on this, e.g. here, here, and here

bytecodealliance/wasmtime

A lightweight WebAssembly runtime that is fast, secure, and standards-compliant - bytecodealliance/wasmtime

rfcs/accepted/wasmtime-debugging-v2.md at main · bytecodealliance/rfcs

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Debug: implement call injection to invoke debug event handlers at signal-based traps. by cfallin · Pull Request #11930 · bytecodealliance/wasmtime

(Stacked on top of #11921) This repurposes the code from #11826 to "inject calls": when in a signal handler, we can update the register state to redirect execution upon signal-handler ret...

Debug: add some infrastructure for catching traps, and handle traps properly in Pulley. by cfallin · Pull Request #11921 · bytecodealliance/wasmtime

This is a followup to #11895 where I had disabled a test that failed to emit a debug event for a hostcall-generated trap on a divide-by-zero in Pulley. This PR allows that test to pass, and brings ...

Debugging: add an async debug-step-result interface, and catch traps with it. by cfallin · Pull Request #11826 · bytecodealliance/wasmtime

(Stacked on top of #11769.) As part of the new guest-debugging API, we want to allow the host to execute the debugged guest code asynchronously, receiving its "debug step" results each ti...

Scott Waye (Oct 25 2025 at 14:48):

Notification Bot (Oct 25 2025 at 14:48):

Steve Williams (Oct 25 2025 at 15:21):

Seems problem is worked around by using v0.33.1 - the most recent - as of my current understanding before this regression occurred.

Releases · bytecodealliance/wasmtime