This is a collaborative effort to build a guide that explains how rustc works. The aim of the guide is to help new contributors get oriented to rustc, as well as to help more experienced folks in figuring out some new part of the compiler that they haven't worked on before.

You can read the latest version of the guide here.

You may also find the rustdocs for the compiler itself useful. Note that these are not intended as a guide; it's recommended that you search for the docs you're looking for instead of reading them top to bottom.

For documentation on developing the standard library, see std-dev-guide.

Contributing to the guide

The guide is useful today, but it has a lot of work still to go.

If you'd like to help improve the guide, we'd love to have you! You can find plenty of issues on the issue tracker. Just post a comment on the issue you would like to work on to make sure that we don't accidentally duplicate work. If you think something is missing, please open an issue about it!

In general, if you don't know how the compiler works, that is not a problem! In that case, what we will do is to schedule a bit of time for you to talk with someone who does know the code, or who wants to pair with you and figure it out. Then you can work on writing up what you learned.

In general, when writing about a particular part of the compiler's code, we recommend that you link to the relevant parts of the rustc rustdocs.

Build Instructions

To build a local static HTML site, install mdbook with:

cargo install mdbook mdbook-linkcheck2 mdbook-toc mdbook-mermaid

and execute the following command in the root of the repository:

mdbook build --open

The build files are found in the book/html directory.

Link Validations

We use mdbook-linkcheck2 to validate URLs included in our documentation. Link checking is not run by default locally, though it is in CI. To enable it locally, set the environment variable ENABLE_LINKCHECK=1 like in the following example.

ENABLE_LINKCHECK=1 mdbook serve

Synchronizing josh subtree with rustc

This repository is linked to rust-lang/rust as a josh subtree. You can use the following commands to synchronize the subtree in both directions.

You'll need to install josh-proxy locally via

cargo install josh-proxy --git https://github.com/josh-project/josh --tag r24.10.04

Older versions of josh-proxy may not round trip commits losslessly so it is important to install this exact version.

Pull changes from `rust-lang/rust` into this repository

Checkout a new branch that will be used to create a PR into rust-lang/rustc-dev-guide

Run the pull command

cargo run --manifest-path josh-sync/Cargo.toml rustc-pull

Push the branch to your fork and create a PR into rustc-dev-guide

Push changes from this repository into `rust-lang/rust`

NOTE: If you use Git protocol to push to your fork of rust-lang/rust, ensure that you have this entry in your Git config, else the 2 steps that follow would prompt for a username and password:

[url "git@github.com:"]
insteadOf = "https://github.com/"

Run the push command to create a branch named <branch-name> in a rustc fork under the <gh-username> account
```
cargo run --manifest-path josh-sync/Cargo.toml rustc-push <branch-name> <gh-username>
```
Create a PR from <branch-name> into rust-lang/rust

Minimal git config

For simplicity (ease of implementation purposes), the josh-sync script simply calls out to system git. This means that the git invocation may be influenced by global (or local) git configuration.

You may observe "Nothing to pull" even if you know rustc-pull has something to pull if your global git config sets fetch.prunetags = true (and possibly other configurations may cause unexpected outcomes).

To minimize the likelihood of this happening, you may wish to keep a separate minimal git config that only has [user] entries from global git config, then repoint system git to use the minimal git config instead. E.g.

GIT_CONFIG_GLOBAL=/path/to/minimal/gitconfig GIT_CONFIG_SYSTEM='' cargo run --manifest-path josh-sync/Cargo.toml -- rustc-pull

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