wasmerio/wasmer · critical · panic

not implemented

Error message

not implemented

What it means

Trap::to_trap is a stub: its body is a bare unimplemented!(), so calling it panics with "not implemented" every time. The method is documented to return Option<TrapCode> if the Trap carries a trap code, but that logic was never written. Any caller relying on it to classify a trap hits an unconditional panic, independent of the Trap variant (signal_trap, lib, etc.).

Source

Thrown at lib/vm/src/trap/trap.rs:80

    /// Internally saves a backtrace when constructed.
    pub fn user(err: Box<dyn Error + Send + Sync>) -> Self {
        Self::User(err)
    }

    /// Construct a new Wasm trap with the given source location and backtrace.
    ///
    /// Internally saves a backtrace when constructed.
    pub fn wasm(pc: usize, backtrace: Backtrace, signal_trap: Option<TrapCode>) -> Self {
        Self::Wasm {
            pc,
            backtrace,
            signal_trap,
        }
    }

    /// Returns trap code, if it's a Trap
    pub fn to_trap(self) -> Option<TrapCode> {
        unimplemented!()
    }

    /// Construct a new Wasm trap with the given trap code.
    ///
    /// Internally saves a backtrace when constructed.
    pub fn lib(trap_code: TrapCode) -> Self {
        let backtrace = Backtrace::new_unresolved();
        Self::Lib {
            trap_code,
            backtrace,
        }
    }

    /// Construct a new OOM trap with the given source location and trap code.
    ///
    /// Internally saves a backtrace when constructed.
    pub fn oom() -> Self {
        let backtrace = Backtrace::new_unresolved();

View on GitHub (pinned to 8c4b9ee9d3)

Solutions

1. Do not call to_trap; inspect the Trap variant directly and map signal-based traps to TrapCode yourself.
2. Implement to_trap locally: match the internal enum (e.g. Trap::Lib { trap_code, .. } => Some(trap_code), _ => None).
3. Use the library's existing trap-code accessor/APIs (e.g. Trap::lib / downcast helpers) instead.
4. File/patch upstream: the method body is an unfinished stub.

Example fix

// before
let code = trap.to_trap(); // panics: unimplemented!()

// after (local helper)
fn trap_code_of(trap: &Trap) -> Option<TrapCode> {
    match trap {
        Trap::Lib { trap_code, .. } => Some(*trap_code),
        _ => None,
    }
}

// narrow Trap variants yourself instead of calling to_trap()
fn trap_code_of(trap: &Trap) -> Option<TrapCode> {
    match trap {
        Trap::Lib { trap_code, .. } => Some(*trap_code),
        _ => None,
    }
}

let code = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| trap.to_trap()))
    .ok()
    .flatten()
    .or_else(|| trap_code_of(&trap));

When it happens

Trigger: Any call to Trap::to_trap() — e.g. code converting a raised Trap into a TrapCode when handling a wasm fault — panics immediately regardless of input.

Common situations: Embedder code classifying runtime faults (e.g. turning SIGSEGV-derived traps into TrapCode::MemoryOutOfBounds), custom host integrations, or ported code from wasmer versions where to_trap was implemented.

Related errors

• dwarf relocation size for personality not supported: {}
• dwarf relocation size for LSDA not supported: {}
• eh pointer encoding {eh_pe:?} not supported for symbol targe
• write_offset not yet implemented
• write_offset_at not yet implemented

AI-assisted analysis of wasmerio/wasmer@8c4b9ee9d3 (2026-09-01). Data as JSON: /api/errors/27cb73f292bbdb90. Report an issue: GitHub.