test_override_env failing during `make check`

[wizeman]

Using commit 7fbbfe6 I am experiencing this failure during make check:

metrics saved to: tmp/check-stage2-T-x86_64-unknown-linux-gnu-H-x86_64-unknown-linux-gnu-std-metrics.json
failures:

---- io::process::tests::test_override_env::green stdout ----
    task 'io::process::tests::test_override_env::green' failed at 'called `Result::unwrap()` on an `Err` value: no such file or directory (no such file or directory)', /tmp/nix-build-rustc-0.12.0-pre-7fbbfe6bf.drv-0/git-export/src/libcore/result.rs:808


---- io::process::tests::test_override_env::native stdout ----
    task 'io::process::tests::test_override_env::native' failed at 'receiving on a closed channel', /tmp/nix-build-rustc-0.12.0-pre-7fbbfe6bf.drv-0/git-export/src/libsync/comm/mod.rs:837



failures:
    io::process::tests::test_override_env::green
    io::process::tests::test_override_env::native

test result: FAILED. 833 passed; 2 failed; 63 ignored; 0 measured

task '<main>' failed at 'Some tests failed', /tmp/nix-build-rustc-0.12.0-pre-7fbbfe6bf.drv-0/git-export/src/libtest/lib.rs:243
make: *** [tmp/check-stage2-T-x86_64-unknown-linux-gnu-H-x86_64-unknown-linux-gnu-std.ok] Error 101

Initially I thought it was because my OS (NixOS) did not install env in /usr/bin (in fact, /usr doesn't even exist, but env is in the PATH), but even then, that does not explain why other env tests succeed (such as test_add_to_env, which is almost exactly the same code as test_override_env).

However, if I copy/paste the code from the test into a new program and run it, it seems to work fine.

Furthermore, this exact make check failure seems to be repeatable, even after updating to a newer commit and compiling everything from scratch.

This seems quite mysterious to me... any ideas as to what the problem might be?

[wizeman]

Ah, I just discovered what the problem is.

test_override_env, like the name alludes to, spawns an env subprocess, but before that (and unlike other tests) it completely deletes all environment variables (except that it adds a new one, just for testing). This means that $PATH will be empty.

The subprocess is executed using execvp(), and its man page says:

The (...) execvp() (... function ...) duplicates the actions of the shell in searching for an executable file if the specified filename does not contain a slash (/) character. The file is sought in the colon-separated list of directory pathnames specified in the PATH environment variable.

_If this variable isn't defined, the path list defaults to the current directory followed by the list of directories returned by confstr(CS_PATH). (This confstr(3) call typically returns the value "/bin:/usr/bin".)

Since env is not in /bin nor /usr/bin in my system, the test fails.

[wizeman]

I have a fix for this, will submit soon.