Can't cross-compile doc tests with Cargo

[asomers]

I have a project that uses unit, functional, and doc tests. When I run “cargo test”, all three sets of tests execute. But when I cross-compile, only the unit and functional tests do. The output makes no mention of Doc-tests at all. I can't find anything in the cargo docs that suggests why this should be impossible. For the case where the host is a 64-bit system and the target is the 32-bit ABI of the same architecture, it ought to work. Indeed, the unit and functional tests run and pass. Only the doc tests fail to build. My host is x86_64 FreeBSD and I’m trying to cross test i686 FreeBSD.

> cargo --version
cargo 0.21.0 (5b4b8b2ae 2017-08-12)
> freebsd-version 
11.0-RELEASE-p9
> cargo test --target=i686-unknown-freebsd -v

[alexcrichton]

This is currently intentional as while Cargo has infrastructure for running cross-compiled tests and handling all that I don't believe this is implemented and/or handled in rustdoc. I'm not sure if rustdoc --test --target ... will work as expected.

[asomers]

Good explanation, @alexcrichton . It looks like rustdoc ignores --target when used with --test. I've opened a separate issue for that.
rust-lang/rust#44404