Deps: backtrace

[ehuss]

This issue is for working through the implementation issues for compiling backtrace.

The backtrace crate provides runtime backtraces. It is on by default (for all platforms?). This currently requires a C compiler.

#46439 tracks using a pure-Rust implementation.

I'm not sure exactly how this will fit in the std-aware Cargo story.

[bjorn3]

rust-lang/rust#46439 has been closed.

[ehuss]

Yea, that goes a long way towards making things easier to build. I'd like to keep this issue open to track how to deal with the backtrace feature. AFAIK, it is always enabled (and is force-enabled in Cargo build-std), but there is likely some more consideration needed for platforms where backtrace is not supported. This is somewhat related to #13, where the story for handling features hasn't been fully defined.

[jrose-signal]

Per rust-lang/rust#130320, it would also be great to support backtraces sans symbolication for code size reasons. (I'm mentioning that here because I suspect it needs to become a feature to be any use, even though there is probably also std work involved.)