Doctests fail with cross compilation, causing test_in_svsm builds to fail to compile with rust nightly toolchain 2025-05-17 and later #705
Description
Prior to nightly-2025-05-17, rust would not compile doctests as part of cargo test when cross compiling. In this toolchain version, that was fixed so doctests are part of it: rust-lang/cargo#15462. When building the "test_in_svsm" binaries (e.g. make bin/test-kernel.elf), cargo test is invoked to cross compile the unit tests. With the nightly-2025-05-17 toolchain, this therefore tries to build the doctests for the x86_64-unknown-none target. However, these tests fail to compile on that target. This is partly due to them not specifying no_std, but even if that is given there are other errors.
These are a few options for resolving:
- Use the environment variable
RUSTDOC=trueforcargo test, which makes cargo think there are no doctests at all. This basically replicates what the toolchain was doing anyway prior to this version. - Edit the problematic doctests (which may be all of them?) to have per-target ignores to say they shouldn't be cross-compiled.
- Set up our unit test runner to work with doctests as well. I don't know why unit tests and doctest are treated differently, but hopefully a lot of the same infrastructure can be shared. I spent a bit of time trying to do this, but it was nontrivial for me. I also found this comment indicating that doctest integration with custom test runners is not supported, so this might just not be possible at the moment.
I'm inclined to send in a PR for option 1.