`rustup component add llvm-bitcode-linker` should imply `rustup component add llvm-tools`

[usamoi]

rustup component add llvm-bitcode-linker should imply rustup component add llvm-tools. If llvm-bitcode-linker is installed but llvm-tools is not installed, linking with llvm-bitcode-linker causes confusing errors since it tries to use system llvm.

confusing errors

error: linking with `llvm-bitcode-linker` failed: exit status: 1
  |
  = note:  "llvm-bitcode-linker" "<1 object files omitted>" "<sysroot>/lib/rustlib/nvptx64-nvidia-cuda/lib/{librustc_std_workspace_core-*,libcore-*,libcompiler_builtins-*}.rlib" "-L" "/tmp/rustcnJ2SL2/raw-dylibs" "--target" "nvptx64-nvidia-cuda" "--target-cpu" "sm_30" "-L" "<sysroot>/lib/rustlib/nvptx64-nvidia-cuda/lib/self-contained" "-o" "/usamoi/playground/ru/target/nvptx64-nvidia-cuda/debug/deps/ru-f4c0ba032d0d0a83.ptx" "-O0" "--debug"
  = note: some arguments are omitted. use `--verbose` to show all linker arguments
  = note: Error: llvm-link failed to link files ["/usamoi/playground/ru/target/nvptx64-nvidia-cuda/debug/deps/ru-f4c0ba032d0d0a83.aiqzghoh0fmgtru173eaewpev.rcgu.o", "/home/usamoi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/nvptx64-nvidia-cuda/lib/librustc_std_workspace_core-3fd0694f720b1c16.rlib", "/home/usamoi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/nvptx64-nvidia-cuda/lib/libcore-4a9eff19b785368f.rlib", "/home/usamoi/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/nvptx64-nvidia-cuda/lib/libcompiler_builtins-4240302f1379e85f.rlib"]
          ␛[2m2025-03-26T11:10:55.850207Z␛[0m ␛[32m INFO␛[0m ␛[2mllvm_bitcode_linker::linker␛[0m␛[2m:␛[0m Linking 4 files using llvm-link
          ␛[2m2025-03-26T11:10:55.861321Z␛[0m ␛[31mERROR␛[0m ␛[2mllvm_bitcode_linker::linker␛[0m␛[2m:␛[0m llvm-link returned with Exit status: exit status: 1
           stdout: 
           stderr: error: Invalid record

reproduce

1. cargo init

2. src/main.rs

#![no_std]
#![no_main]

#[panic_handler]
fn panic_handler(_: &core::panic::PanicInfo<'_>) -> ! {
    loop {}
}

3. rustup-toolchain

nightly

4. rustup component remove llvm-tools

5. rustup component add llvm-bitcode-linker

6. RUSTFLAGS="-Clinker=llvm-bitcode-linker" cargo build --target nvptx64-nvidia-cuda

[djc]

It is not obvious to me why you think this should be the case. rustup installs toolchain components (llvm-tools), not individual binaries (llvm-bitcode-linker). You could argue that rustup should understand what binaries are shipped in what (non-default) components, but that mapping could be a little bit tricky.

[usamoi]

llvm-bitcode-linker is a component too. The component llvm-bitcode-linker relies on the component llvm-tools to work. However, rustup does not automatically handle this.

[djc]

I'm not sure we want to implicitly install the llvm-tools component as well, but we could at least emit a warning that the dependended upon component is not currently installed for the toolchain.

[ChrisDenton]

I would prefer that dependencies be encoded in the manifest we get rather than something rustup hardcodes, whether we implicitly install or just warn. Things can change over time and rust-lang/rust knows best which components it ships and their relationships.

[rami3l]

100% agree; we need to discuss with upstream first to confirm what needs to be done on our side.