How to trace the cause of an error result?

Question

When writing code that uses Result type, you may want different behavior for users and developers.

• When writing an application that gracefully han

Answer 1

A result by itself doesn't have any backtrace information, but you can add it to custom error types.

The error_chain crate is an example which generates an error type for you, for which you get backtrace generation for free when the RUST_BACKTRACE environment variable is set.

You could also use the backtrace library directly and do it yourself.

Answer 2

If you use anyhow you can get this for free! The catch is you need to use nightly and enable an environment variable:

RUST_BACKTRACE=1 cargo +nightly run

This is the tracking issue for stabilisation, and a PR to stabilise it. Looks like there is some disagreement about whether it needs to work in no_std before being stabilised or something like that.