Debug backtrace memory and line number of WASM

[clearloop]

DESC

Ref to #1, we can see that wasmer get both line number and memory of wasm, let's find out how it works.

Line number and memory of wasm

error: failed to run `target/wasm32-unknown-unknown/debug/bt.wasm`
│   1: RuntimeError: unreachable
           at __rust_start_panic (bt.wasm[67]:0x1cda)
           at rust_panic (bt.wasm[66]:0x1cce)
           at std::panicking::rust_panic_with_hook::hc5713da015ebaa19 (bt.wasm[65]:0x1c9e)
           at std::panicking::begin_panic::{{closure}}::h8e62ab0ea555186f (bt.wasm[2]:0x26e)
           at std::sys_common::backtrace::__rust_end_short_backtrace::h34a944558df1326a (bt.wasm[36]:0xfba)
           at std::panicking::begin_panic::h03c636dac2b8fb70 (bt.wasm[0]:0x15c)
           at _start (bt.wasm[55]:0x1a65)
╰─> 2: unreachable

[clearloop]

Error Display

impl fmt::Display for RuntimeError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "RuntimeError: {}", self.message())?;
        let trace = self.trace();
        if trace.is_empty() {
            return Ok(());
        }
        for frame in self.trace().iter() {
            let name = frame.module_name();
            let func_index = frame.func_index();                                                                                                                                                                                                                                
            writeln!(f)?;
            write!(f, "    at ")?;
            match frame.function_name() {
                Some(name) => match rustc_demangle::try_demangle(name) {
                    Ok(name) => write!(f, "{}", name)?,
                    Err(_) => write!(f, "{}", name)?,
                },
                None => write!(f, "<unnamed>")?,
            }
            write!(
                f,
                " ({}[{}]:0x{:x})",
                name,
                func_index,
                frame.module_offset()
            )?;
        }
        Ok(())
    }
}

• The func_index above is the function index in name_section
• The code_offset above is code positon from start