Implement the panic profile option

[alexcrichton]

This is the Cargo half of the implementation of RFC 1513 which adds a new
profile.*.panic option to customize the -C panic argument to the compiler.
This is not passed by default and can otherwise be specified as abort or
unwind on the nightly compiler.

The profile.*.panic option is only used from the top-level crate, not each
crate individually. This means that applications should customize this value as
they see fit, and libraries will only use their own value when they're being
tested.

Cargo also has specific knowledge that when testing a crate it can't pass
-C panic=abort for now as the default test harness requires panic=unwind.
This essentially just means that cargo test will continue to work for crates
that specify panic=abort in Cargo.toml.

[alexcrichton]

r? @brson

[rust-highfive]

r? @wycats

(rust_highfive has picked a reviewer for you, use r? to override)

[steveklabnik]

Any chance we can get this merged sometime soon? Eagerly awaiting 😄

[bors]

☔ The latest upstream changes (presumably #2685) made this pull request unmergeable. Please resolve the merge conflicts.

[wycats]

@bors r+

[bors]

📌 Commit b6e0fe9 has been approved by wycats

[bors]

⌛ Testing commit b6e0fe9 with merge aaea05d...

[bors]

💔 Test failed - cargo-linux-64

[alexcrichton]

@bors: r=wycats

[bors]

📌 Commit 75848a2 has been approved by wycats

[bors]

⌛ Testing commit 75848a2 with merge 259324c...

[bors]

☀️ Test successful - cargo-cross-linux, cargo-linux-32, cargo-linux-64, cargo-mac-32, cargo-mac-64, cargo-win-gnu-32, cargo-win-gnu-64, cargo-win-msvc-32, cargo-win-msvc-64

[alexbool]

Seems like there's a bug in your implementation.
When I build my crate with

[profile.dev]
panic = "abort"

I get an error if my crate depends on any crate that builds using a build.rs.
The failure looks as following:

$ cargo build --release --verbose
...
   Compiling kernel32-sys v0.2.2
     Running `rustc /Users/alexbool/.cargo/registry/src/gh.neting.cc-1ecc6299db9ec823/kernel32-sys-0.2.2/build.rs --crate-name build_script_build --crate-type bin -g --out-dir /Users/alexbool/Documents/IdeaProjects/rust/mycrate/target/release/build/kernel32-sys-d6afa5bd3d7cfaef --emit=dep-info,link -L dependency=/Users/alexbool/Documents/IdeaProjects/rust/mycrate/target/release/deps -L dependency=/Users/alexbool/Documents/IdeaProjects/rust/mycrate/target/release/deps --extern build=/Users/alexbool/Documents/IdeaProjects/rust/mycrate/target/release/deps/libbuild-493a7b0628804707.rlib --cap-lints allow`
error: the crate `build` is compiled with the panic strategy `abort` which is incompatible with this crate's strategy of `unwind`
error: aborting due to previous error
Build failed, waiting for other jobs to finish...
error: Could not compile `kernel32-sys`.

[alexcrichton]

Thanks for the report @alexbool! I unfortunately can't seem to reproduce easily, could you open an issue with some instructions about how to reproduce as well?

[tomaka]

@alexcrichton I didn't test a lot, but I think the issue appears when you have a different value for panic for the dev and release profiles.

[alexbool]

@alexcrichton the issue is #2726 :)

[alexcrichton]

Thanks!