is bootstrapped and in general, some of the technical details of the build
system.
-## Using rustbuild
+Note that this README only covers internal information, not how to use the tool.
+Please check [bootstrapping dev guide][bootstrapping-dev-guide] for further information.
-The rustbuild build system has a primary entry point, a top level `x.py` script:
+[bootstrapping-dev-guide]: https://rustc-dev-guide.rust-lang.org/building/bootstrapping.html
-```sh
-$ python ./x.py build
-```
-
-Note that if you're on Unix, you should be able to execute the script directly:
-
-```sh
-$ ./x.py build
-```
-
-The script accepts commands, flags, and arguments to determine what to do:
-
-* `build` - a general purpose command for compiling code. Alone, `build` will
- bootstrap the entire compiler, and otherwise, arguments passed indicate what to
- build. For example:
-
- ```
- # build the whole compiler
- ./x.py build --stage 2
-
- # build the stage1 compiler
- ./x.py build
-
- # build stage0 libstd
- ./x.py build --stage 0 library/std
-
- # build a particular crate in stage0
- ./x.py build --stage 0 library/test
- ```
-
- If files that would normally be rebuilt from stage 0 are dirty, the rebuild can be
- overridden using `--keep-stage 0`. Using `--keep-stage n` will skip all steps
- that belong to stage n or earlier:
-
- ```
- # build stage 1, keeping old build products for stage 0
- ./x.py build --keep-stage 0
- ```
-
-* `test` - a command for executing unit tests. Like the `build` command, this
- will execute the entire test suite by default, and otherwise, it can be used to
- select which test suite is run:
-
- ```
- # run all unit tests
- ./x.py test
-
- # execute tool tests
- ./x.py test tidy
-
- # execute the UI test suite
- ./x.py test src/test/ui
-
- # execute only some tests in the UI test suite
- ./x.py test src/test/ui --test-args substring-of-test-name
-
- # execute tests in the standard library in stage0
- ./x.py test --stage 0 library/std
-
- # execute tests in the core and standard library in stage0,
- # without running doc tests (thus avoid depending on building the compiler)
- ./x.py test --stage 0 --no-doc library/core library/std
+## Introduction
- # execute all doc tests
- ./x.py test src/doc
- ```
+The build system defers most of the complicated logic managing invocations
+of rustc and rustdoc to Cargo itself. However, moving through various stages
+and copying artifacts is still necessary for it to do. Each time rustbuild
+is invoked, it will iterate through the list of predefined steps and execute
+each serially in turn if it matches the paths passed or is a default rule.
+For each step rustbuild relies on the step internally being incremental and
+parallel. Note, though, that the `-j` parameter to rustbuild gets forwarded
+to appropriate test harnesses and such.
-* `doc` - a command for building documentation. Like above, can take arguments
- for what to document.
-
-## Configuring rustbuild
-
-rustbuild offers a TOML-based configuration system with a `config.toml`
-file. An example of this configuration can be found at `config.toml.example`,
-and the configuration file can also be passed as `--config path/to/config.toml`
-if the build system is being invoked manually (via the python script).
-
-You can generate a config.toml using `./configure` options if you want to automate creating the file without having to edit it.
-
-Finally, rustbuild makes use of the [cc-rs crate] which has [its own
-method][env-vars] of configuring C compilers and C flags via environment
-variables.
-
-[cc-rs crate]: https://github.com/alexcrichton/cc-rs
-[env-vars]: https://github.com/alexcrichton/cc-rs#external-configuration-via-environment-variables
-
-## Build stages
+## Build phases
The rustbuild build system goes through a few phases to actually build the
compiler. What actually happens when you invoke rustbuild is:
-1. The entry point script, `x.py` is run. This script is
- responsible for downloading the stage0 compiler/Cargo binaries, and it then
- compiles the build system itself (this folder). Finally, it then invokes the
- actual `bootstrap` binary build system.
+1. The entry point script(`x` for unix like systems, `x.ps1` for windows systems,
+ `x.py` cross-platform) is run. This script is responsible for downloading the stage0
+ compiler/Cargo binaries, and it then compiles the build system itself (this folder).
+ Finally, it then invokes the actual `bootstrap` binary build system.
2. In Rust, `bootstrap` will slurp up all configuration, perform a number of
sanity checks (whether compilers exist, for example), and then start building the
stage0 artifacts.
The goal of each stage is to (a) leverage Cargo as much as possible and failing
that (b) leverage Rust as much as possible!
-## Incremental builds
-
-You can configure rustbuild to use incremental compilation with the
-`--incremental` flag:
-
-```sh
-$ ./x.py build --incremental
-```
-
-The `--incremental` flag will store incremental compilation artifacts
-in `build/<host>/stage0-incremental`. Note that we only use incremental
-compilation for the stage0 -> stage1 compilation -- this is because
-the stage1 compiler is changing, and we don't try to cache and reuse
-incremental artifacts across different versions of the compiler.
-
-You can always drop the `--incremental` to build as normal (but you
-will still be using the local nightly as your bootstrap).
-
## Directory Layout
This build system houses all output under the `build` directory, which looks
# system will link (using hard links) output from stageN-{std,rustc} into
# each of these directories.
#
- # In theory, there is no extra build output in these directories.
+ # In theory these are working rustc sysroot directories, meaning there is
+ # no extra build output in these directories.
stage1/
stage2/
stage3/
```
-## Cargo projects
-
-The current build is unfortunately not quite as simple as `cargo build` in a
-directory, but rather the compiler is split into three different Cargo projects:
-
-* `library/std` - the standard library
-* `library/test` - testing support, depends on libstd
-* `compiler/rustc` - the actual compiler itself
-
-Each "project" has a corresponding Cargo.lock file with all dependencies, and
-this means that building the compiler involves running Cargo three times. The
-structure here serves two goals:
-
-1. Facilitating dependencies coming from crates.io. These dependencies don't
- depend on `std`, so libstd is a separate project compiled ahead of time
- before the actual compiler builds.
-2. Splitting "host artifacts" from "target artifacts". That is, when building
- code for an arbitrary target, you don't need the entire compiler, but you'll
- end up needing libraries like libtest that depend on std but also want to use
- crates.io dependencies. Hence, libtest is split out as its own project that
- is sequenced after `std` but before `rustc`. This project is built for all
- targets.
-
-There is some loss in build parallelism here because libtest can be compiled in
-parallel with a number of rustc artifacts, but in theory, the loss isn't too bad!
-
-## Build tools
-
-We've actually got quite a few tools that we use in the compiler's build system
-and for testing. To organize these, each tool is a project in `src/tools` with a
-corresponding `Cargo.toml`. All tools are compiled with Cargo (currently having
-independent `Cargo.lock` files) and do not currently explicitly depend on the
-compiler or standard library. Compiling each tool is sequenced after the
-appropriate libstd/libtest/librustc compile above.
-
## Extending rustbuild
-So, you'd like to add a feature to the rustbuild build system or just fix a bug.
-Great! One of the major motivational factors for moving away from `make` is that
-Rust is in theory much easier to read, modify, and write. If you find anything
-excessively confusing, please open an issue on this, and we'll try to get it
-documented or simplified, pronto.
+When you use the bootstrap system, you'll call it through the entry point script
+(`x`, `x.ps1`, or `x.py`). However, most of the code lives in `src/bootstrap`.
+`bootstrap` has a difficult problem: it is written in Rust, but yet it is run
+before the Rust compiler is built! To work around this, there are two components
+of bootstrap: the main one written in rust, and `bootstrap.py`. `bootstrap.py`
+is what gets run by entry point script. It takes care of downloading the `stage0`
+compiler, which will then build the bootstrap binary written in Rust.
-First up, you'll probably want to read over the documentation above, as that'll
-give you a high level overview of what rustbuild is doing. You also probably
-want to play around a bit yourself by just getting it up and running before you
-dive too much into the actual build system itself.
+Because there are two separate codebases behind `x.py`, they need to
+be kept in sync. In particular, both `bootstrap.py` and the bootstrap binary
+parse `config.toml` and read the same command line arguments. `bootstrap.py`
+keeps these in sync by setting various environment variables, and the
+programs sometimes have to add arguments that are explicitly ignored, to be
+read by the other.
-After that, each module in rustbuild should have enough documentation to keep
-you up and running. Some general areas that you may be interested in modifying
-are:
+Some general areas that you may be interested in modifying are:
* Adding a new build tool? Take a look at `bootstrap/tool.rs` for examples of
other tools.
Changes that do not affect contributors to the compiler or users
building rustc from source don't need an update to `VERSION`.
-If you have any questions, feel free to reach out on the `#t-infra` channel in
-the [Rust Zulip server][rust-zulip] or ask on internals.rust-lang.org. When
-you encounter bugs, please file issues on the rust-lang/rust issue tracker.
+If you have any questions, feel free to reach out on the `#t-infra/bootstrap` channel
+at [Rust Bootstrap Zulip server][rust-bootstrap-zulip]. When you encounter bugs,
+please file issues on the [Rust issue tracker][rust-issue-tracker].
-[rust-zulip]: https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra
+[rust-bootstrap-zulip]: https://rust-lang.zulipchat.com/#narrow/stream/t-infra.2Fbootstrap
+[rust-issue-tracker]: https://github.com/rust-lang/rust/issues
projects / rust.git / blobdiff