Cannot run benchmarks with panic = "abort"

[AaronFriel]

The following error is obtained when running cargo bench, with the a panic = "abort" option in cargo.toml:

error: the linked panic runtime `panic_unwind` is not compiled with this crate's panic strategy `abort`

The cargo.toml needs to set the panic behavior in [profile.bench], e.g.:

cargo.toml:

[package]
name = "foobar"
version = "0.1.0"
authors = ["Aaron Friel <mayreply@aaronfriel.com>"]

[dependencies]
clap="^2.13.0"

[profile.bench]
panic = "abort"

[alexcrichton]

Dug a bit more into this today. The dependency actually isn't needed here to trigger the bug, and if you configure profile.test with abort then cargo test is also broken.

The problem here is that libtest, Rust's testing framework, requires the unwind panic mode and is incompatible with panic = "abort". If you configure profile.dev to have panic = "abort", it actually compiles all dependencies with -Cpanic=unwind when you execute cargo test to satisfy this constraint.

The "fix" here would be to ignore panic = "abort" in the bench and test profiles.

[AaronFriel]

The patch in #3175 is confusing to me. Is there any way to run tests or benchmarks with panic="abort"?

[alexcrichton]

Unfortunately no because they all link to libtest which is compiled with panic=unwind :(

[AaronFriel]

I see, and because libtest depends on panics to observe assert! failures, that's the blocking issue?

Is there any work on making an alternative libtest based on Result<>, with an, e.g.: try_assert! that works like try!?

[alexcrichton]

Perhaps yeah, but that's more of a rust-lang/rust issue than a Cargo one.

[AaronFriel]

Interesting. If I were to make an alternative libtest, is there a way to specify that in cargo.toml? Or are tests (and their return types) part of rust-lang/rust?

[alexcrichton]

Yeah you can specify harness = false in which case Cargo will just compile the test as an executable, and then you can link to whatever

[sanmai-NL]

@alexcrichton:
Thanks for fixing the issue in 4a73741 and explaining the test harness design in this thread. I think the issue hasn't been fully resolved though. I had a problem similar to the reporter and I had to find out what was happening from this thread. Can the limitation on panic strategy please be shown as a warning? That would be way less confusing than Cargo silently ignoring the panic profile field.

[alexcrichton]

@sanmai-NL seems reasonable to me! Want to open an issue for that?

[sanmai-NL]

My first reaction to your suggestion is that it would be too much overhead. I can try to make a PR for it straight away. If it doesn't cost you too much time, perhaps you can give some pointers on how to generate an appropriate warning in Cargo, e.g. similar to the current ‘Unknown field’ warning.

[alexcrichton]

Sure yeah sounds good! The best way to generate warnings right now is the add_warning method (called throughout that file). I suspect that this logic would go somewhere in toml.rs.

If that doesn't end up working out though, just let me know