code coverage doesn't see constructors, other lines with hidden panic code

[rob-solana]

Problem

code coverage doesn't see constructors, other lines with hidden panic code, resulting in wrongish coverage metrics, weird artifacts like very basic code (Poh::new()) not being in the "covered" space...

https://codecov.io/gh/solana-labs/solana/src/master/src/poh.rs

rust-lang/rust#55352

Rustc adds line-number information for unhittable panic handlers ...

Proposed Solution

??

[garious]

My understanding is that a panic handler called a landing pad is implicitly added by default and that the way to disable it is passing rustc the -Z no-landing-pads. This test demonstrates how it works: https://github.com/rust-lang/rust/blob/master/src/test/run-pass/no-landing-pads.rs

@rob-solana says he experimented with add that flag after -Zprofile here: https://github.com/solana-labs/solana/blob/master/scripts/coverage.sh#L16, but didn't see any change in coverage.

I think we need to find a way to see what code is being generated with and without that flag to ensure it's not dropped by the Rust toolchain somewhere along the way.

[garious]

@jackcmay, not a super high priority, but can you keep this one on your radar?

[garious]

Another promising flag: -C panic=abort

[bossmc]

A warning, disabling landing pads breaks some other things (e.g. #[expect_panic] tests, and thread death reporting). Maybe that's fine for your use case, but you should be aware 😄.

[stale]

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[stale]

This stale issue has been automatically closed. Thank you for your contributions.