Build-std in cargo.toml is ignored when building

[graykevinb]

Book Section: Minimal Rust Kernel Problem: Even after setting up build-std in Cargo.toml rust build ignores build-std and produces an error. I did add rust-src and it was already installed. Version: rustc 1.72.0-nightly (d59363ad0 2023-06-01)

cargo build --target x86_64-blog_os.json

results in the error:

 Compiling blog_os v0.1.0 (/home/kgray/blog_os)
error[E0463]: can't find crate for core

Workaround: We can specify which crates to compile with the -Z flag.

cargo build -Z build-std=core,compiler_builtins --target x86_64-target.json

Oddly enough the compiler complains that the [unstable] manifest key is unused.

The instructions specified in the book are correct and consistent with the documentation. Thus this is really an issue with rust nightly. However, I wanted to document how I overcame this issue here. If I create a bug report for rust, I will link it here.

[phil-opp]

The [unstable] table should not be part of the Cargo.toml. You need to put it in a new cargo configuration file named .cargo/config.toml.

[graykevinb]

Thank you! I see now that it says that. Closing out.