What is the purpose of rustc-std-workspace-core crate?

Question

Looking at some crates in https://crates.io/ I found that rand is the most downloaded crate and looking in it's dependencies I found the libc crate and in it's dependencies I found the rustc-std-workspace-core which has 0 dependencies with this description: "Explicitly empty crate for rust-lang/rust integration". I could not totally undestand what it means. Can someone explain in more details?

Answer 1

std depends on the libc crate.

Being a dependency of std is... not easy. The way std is built is complicated, it is tightly coupled with the compiler and built with it twice, for bootstrapping.

You can see this dependency is only activated if the rustc-dep-of-std feature is enabled.

This dependency allows std to depend on crates.

See also Plan for removal of rustc-dep-of-std.