Cannot build + install with `target = ["thumbv7m-none-eabi"]`

[osenft]

Steps to reproduce:

1. Get gcc-arm-none-eabi-10-2020-q4-major-x86_64-linux.tar.bz2 from the ARM developer website. Install and make available via PATH.
2. Get https://static.rust-lang.org/dist/rustc-nightly-src.tar.gz and extract.
3. Copy config.toml.example to config.toml and make the following changes:
   • Set target = ["thumbv7m-none-eabi"].
   • Configure prefix and sysconfigdir to a path in your home directory.
4. Run python3.9 x.py build. This will be successful.
5. Run python3.9 x.py install.

Expected behavior:
Rust for target thumbv7m-none-eabi is built and installed.

Actual behavior:
The build/install fails with the following error message:

   Compiling rustc-std-workspace-core v1.99.0 (/home/osk/src/rust-thumb/rustc-nightly-src/library/rustc-std-workspace-core)
   Compiling alloc v0.0.0 (/home/osk/src/rust-thumb/rustc-nightly-src/library/alloc)
    Finished release [optimized] target(s) in 10.00s
Copying stage2 std from stage2 (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu / thumbv7m-none-eabi)
error: The argument '--package <SPEC>' was provided more than once, but cannot be used multiple times

USAGE:
    cargo rustdoc --features <FEATURES>... --jobs <N> --manifest-path <PATH> --package <SPEC> --release --target <TRIPLE>... -Z <FLAG>...

For more information try --help


command did not execute successfully: "/home/osk/src/rust-thumb/rustc-nightly-src/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "rustdoc" "--target" "thumbv7m-none-eabi" "-Zbinary-dep-depinfo" "-j" "12" "--release" "-p" "alloc" "--manifest-path" "/home/osk/src/rust-thumb/rustc-nightly-src/library/alloc/Cargo.toml" "--features" "compiler-builtins-mem compiler-builtins-c" "-p" "core" "--" "--markdown-css" "rust.css" "--markdown-no-toc" "-Z" "unstable-options" "--resource-suffix" "1.54.0" "--index-page" "/home/osk/src/rust-thumb/rustc-nightly-src/src/doc/index.md"
expected success, got: exit code: 1


failed to run: /home/osk/src/rust-thumb/rustc-nightly-src/build/bootstrap/debug/bootstrap install
Build completed unsuccessfully in 0:08:12

[ehuss]

It looks like std docs cannot be built for any no_std target. This is because the set of crates to document is hard-coded here, and std_cargo hard-codes the -p argument for no_std targets.

I think at a minimum, the std docs should just be disabled for no_std targets automatically.

Getting docs building for a no_std target might be an uphill battle since they haven't been functional for some time (if ever?). There are likely various edge cases that will need fixing (or hopefully not!). Getting the Std doc builder and the std_cargo function to coordinate might be a little awkward, but such is life in a complex build system.

[Mark-Simulacrum]

Hmm. Yeah, this seems a bit painful to fix. I don't mind some not-too-hacky code... not sure how exactly to go about it though.

[osenft]

Thanks, @ehuss! Changing krates to an empty array allowed x.py install to complete.

Now that I understand what the problem is, I realized that I could have simply set docs = false in config.toml (which also works). If nothing at all, would it make sense to print a hint in case the docs step fails?