Fix: Ignore CARGO_BUILD_TARGET in tests

[bryango]

Related: NixOS/nixpkgs#298108

When build target triples are explicitly specified, the layout of the target directory is changed from target/... to target/<triple>/.... See: https://doc.rust-lang.org/cargo/guide/build-cache.html. This caused bin tests failures in tests/profile.rs.

For example, in nixpkgs CARGO_BUILD_TARGET is automatically set up, and we observe the following test failures:

rust-cbindgen>      Running tests/profile.rs (target/x86_64-unknown-linux-gnu/release/deps/profile-fec32decafabbade)
rust-cbindgen> running 3 tests
rust-cbindgen> test bin_explicit_release_build ... FAILED
rust-cbindgen> test bin_explicit_debug_build ... FAILED
rust-cbindgen> test bin_default_uses_debug_build ... FAILED
rust-cbindgen> failures:
rust-cbindgen> ---- bin_explicit_release_build stdout ----
rust-cbindgen> thread 'bin_explicit_release_build' panicked at tests/profile.rs:99:5:
rust-cbindgen> assertion `left == right` failed
rust-cbindgen>   left: ["release", "x86_64-unknown-linux-gnu"]
rust-cbindgen>  right: ["release"]
rust-cbindgen> note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
rust-cbindgen> ---- bin_explicit_debug_build stdout ----
rust-cbindgen> thread 'bin_explicit_debug_build' panicked at tests/profile.rs:93:5:
rust-cbindgen> assertion `left == right` failed
rust-cbindgen>   left: ["debug", "x86_64-unknown-linux-gnu"]
rust-cbindgen>  right: ["debug"]
rust-cbindgen> ---- bin_default_uses_debug_build stdout ----
rust-cbindgen> thread 'bin_default_uses_debug_build' panicked at tests/profile.rs:87:5:
rust-cbindgen> assertion `left == right` failed
rust-cbindgen>   left: ["debug", "x86_64-unknown-linux-gnu"]
rust-cbindgen>  right: ["debug"]
rust-cbindgen> failures:
rust-cbindgen>     bin_default_uses_debug_build
rust-cbindgen>     bin_explicit_debug_build
rust-cbindgen>     bin_explicit_release_build
rust-cbindgen> test result: FAILED. 0 passed; 3 failed; 0 ignored; 0 measured; 3 filtered out; finished in 0.59s
rust-cbindgen> error: test failed, to rerun pass `--test profile`

See: NixOS/nixpkgs#298108 (comment)

This patch proposes that we simply ignore the CARGO_BUILD_TARGET env var in tests to avoid such problems. A new test is introduced to ensure the correct behavior.

[emilio]

Looks sensible.

[bryango]

New commit: it turns out that std::env::set_var is unsafe: the set_var in bin tests in tests/profile.rs leaked through the threads and caused lib tests to fail.

To mitigate this problem we simply remove the CARGO_BUILD_TARGET variable in lib tests as well. This also improves correctness. Meanwhile we put std::env::set_var and remove_var in unsafe blocks as would be required by Rust 2024.

[bryango]

Friendly ping @emilio for re-review 😆

[emilio]

Ok, looks good with #[serial] added, thanks!

[bryango]

Indeed, thank you very much! Fixed in a new commit, awaiting CI!

[emilio]

Thanks!

[bryango]

Thank you very much for merging! By the way, when would you expect to have the next point release? This information will help us downstream (such as nixpkgs) decide whether to update the patch or just wait for the next release 😆