`libc` crate tests do not run (or even compile) on linux targets in CI

[tamird]

#1536 added the ability to mark functions as const, along with a test in https://github.com/rust-lang/libc/blob/42e5708d3c0cfcf68f6ffea45eed7e1732dbd7ec/tests/const_fn.rs. Unfortunately this file is completely dead due to the combination of #[cfg(target_os = "linux")] in it and the behavior introduced in 3eb4a48 which skips building the libc crate when docker: true, which is the case for all linuxes.

This all culminated in the fact that #4105 broke const functions and #4134 failed to fix it in the --no-default-features case. This remains broken.

@tgross35

EDIT: all releases after 0.2.163 which do not contain a fix for this should be yanked.

[tgross35]

Your --no-default-features configuration is not covered, but isn't this test being run by

libc/ci/run.sh

Lines 83 to 92 in 42e5708

	cmd="cargo test --target $target ${LIBC_CI_ZBUILD_STD+"-Zbuild-std"}"
	# Run tests in the `libc` crate
	case "$target" in
	# FIXME(android): unit tests fail to start on Android
	# FIXME(s390x): unit tests fail to locate glibc
	*android*) ;;
	*s390x*) ;;
	*) $cmd
	esac

?

[tamird]

No, it is not, because of exec:

libc/ci/run.sh

Line 80 in 42e5708

exec grep -E "^(PASSED)|(test result: ok)" "${CARGO_TARGET_DIR}/out.log"

Were it not for that exec then --no-default-features would be covered:

libc/ci/run.sh

Line 123 in 42e5708

$cmd --no-default-features

[tgross35]

The branch with exec would only be executed when QEMU is set, which shouldn't be the case for anything x86 (though a command followed by exit is better style than relying on exec, and that grep seems fragile). I also don't think QEMU is set for any of the qemu-system tests, since those were failing when I added the test branch.

$cmd is not the same at lines 91 and 123, it gains --manifest-path libc-test/Cargo.toml in between. This should probably just be --all on platforms where unit tests can run successfully.

[tamird]

The branch with exec would only be executed when QEMU is set, which shouldn't be the case for anything x86 (though a command followed by exit is better style than relying on exec, and that grep seems fragile). I also don't think QEMU is set for any of the qemu-system tests, since those were failing when I added the test branch.

Yes, I think you're right.

$cmd is not the same at lines 91 and 123, it gains --manifest-path libc-test/Cargo.toml in between. This should probably just be --all on platforms where unit tests can run successfully.

Right, I paged this out. Either that or we shouldn't have tests in the libc crate. The situation today is quite inconsistent. Note that --all is a deprecated alias for --workspace.