nif_panicked does not show the panic message

[ishitatsuyuki]

It looks like a unwind handler was added in #264, but it ends up discarding the error object containing the panic message:

rustler/rustler/src/codegen_runtime.rs

Line 126 in 41a85bc

Err(_) => {

As a result, the panic message is not shown to the user, making it confusing and annoying to debug.

    ** (EXIT) an exception was raised:
        ** (ErlangError) Erlang error: :nif_panicked
            (myproject 0.1.0) MyProject.ProcessorNative.parse()
            ...

A workaround is to set panic = 'abort' in Cargo profile, however this is rather ugly.

[evnu]

In RustlerTest.ThreadTest, the test thread panic triggers a panic. That test has additional output from the panic:

thread '<unnamed>' panicked at 'threaded_fac: integer overflow', rustler_tests/native/rustler_test/src/test_thread.rs:11:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I wonder why that is different.

[ishitatsuyuki]

Ah, I tested again and it seems it does give the message. When I encountered this it was #72 however, which effectively borked stderr.

Sorry for the noise.