Change:
let libdir = builder.sysroot_libdir(target_compiler, target); let hostdir = builder.sysroot_libdir(target_compiler, compiler.host); add_to_sysroot(builder, &libdir, &hostdir, &libstd_stamp(builder, compiler, target)); <ins> if compiler.stage == 0 { // special handling for stage0, to make `rustup toolchain link` and `x dist --stage 0` // work for stage0-sysroot // copy bin files from stage0/bin to stage0-sysroot/bin let sysroot = builder.out.join(&compiler.host.triple).join("stage0-sysroot"); let host = compiler.host.triple; let stage0_bin_dir = builder.out.join(&host).join("stage0/bin"); let sysroot_bin_dir = sysroot.join("bin"); t!(fs::create_dir_all(&sysroot_bin_dir)); builder.cp_r(&stage0_bin_dir, &sysroot_bin_dir); // copy all *.so files from stage0/lib to stage0-sysroot/lib let stage0_lib_dir = builder.out.join(&host).join("stage0/lib"); if let Ok(files) = fs::read_dir(&stage0_lib_dir) { for file in files { let file = t!(file); let path = file.path(); if path.is_file() && is_dylib(&file.file_name().into_string().unwrap()) { builder.copy(&path, &sysroot.join("lib").join(path.file_name().unwrap())); } } } // copy codegen-backends from stage0 let sysroot_codegen_backends = builder.sysroot_codegen_backends(compiler); t!(fs::create_dir_all(&sysroot_codegen_backends)); let stage0_codegen_backends = builder .out .join(&host) .join("stage0/lib/rustlib") .join(&host) .join("codegen-backends"); builder.cp_r(&stage0_codegen_backends, &sysroot_codegen_backends); } </ins> } }

Discussion:
Currently, the beta binaries are only present in ; has only the standard library, not any binaries. That causes two issues: doesn't work with stage0-sysroot, meaning there's no way to change the standard library and use those changes at runtime without doing a full stage 1 build doesn't work. This is very rare to want to do, but can be useful when modifying the process itself, to avoid long compile times. Copying the binaries into stage0-sysroot is an easy way to fix both problems at once. Mentoring instructions: Add a call in which copies the whole directory from . <!-- TRIAGEBOTSTART --<!-- TRIAGEBOTASSIGNSTART --<!-- TRIAGEBOTASSIGNDATASTARTTRIAGEBOTASSIGNDATAEND --<!-- TRIAGEBOTASSIGNEND --<!-- TRIAGEBOTEND --
We should also consider renaming to something else; the name is very confusing.
claim
The name is correct though. It is a directory you can pass in as argument to rustc.
so is . I'm not saying the name is wrong, just that it's ambiguous and not intuitive. Honestly I would rather rename all the directories to and change to or something.
is confusing too as already has a libstd. Just one from the bootstrap compiler rather than compiled from the current source.
Ok, then maybe :shrug: nearly anything would be less confusing than just appending IMO
Maybe rename stage0 to bootstrap and stage0-sysroot to stage0, matching stage1-...?
is confusing with the artifacts for , but maybe would work, keeping stage0-sysroot as is and renaming stage1 to stage1-sysroot
Reverted in
I actually wanted to recommend something like this as an alternative std benchmarking workflow. Currently I have to suggest a stage1 build.
I meant is very rare. I agree wanting to use a stage 0 toolchain with just the libstd changes is common :)
do you know when you'll have a chance to follow up here? If you're not planning to follow up, can you please release your assignment on the issue?
Sorry, I didn't follow this item recently. Ok, release it now.
claim I would like to take this issue up [with a bit of mentoring :)] if that's alright. It's my first time contributing!

thanks for looking at it :) the first step is to cherry-pick the changes in to the latest master commit. Then you'll need to fix the bug Mark mentioned in , which I believe has some more details in https://rust- I think it's enough to copy the user-provided over to . Feel free to ask questions here or in https://rust-
It was mentioned that reverted this so I am reopening this unless someone can point me to the, er, revert of the revert?
Useful Links and Points for anyone who wants to work on this: Initial PR : Revert of the Initial PR : Attempt 2 : Revert of attempt 2 : If I am to understand correctly, the revert of the revert was rejected mainly because rust perf () broke. For anyone working on this issue again, here's a point to note: Just copying the entire parent to will not work as pointed out by in zulip as, suppose the rustc is installed in and you try and copy the underlying parent dir which would be . That time, will get all the binaries in . This will however work when the installation is in something like :
My suggestion would be to re-land almost as-is, except with this feature disabled when a custom is set.
claim I'll give this another shot then