46 lines
2.9 KiB
Markdown
46 lines
2.9 KiB
Markdown
# `rustc_driver` and `rustc_interface`
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The [`rustc_driver`] is essentially `rustc`'s `main()` function. It acts as
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the glue for running the various phases of the compiler in the correct order,
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using the interface defined in the [`rustc_interface`] crate.
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The `rustc_interface` crate provides external users with an (unstable) API
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for running code at particular times during the compilation process, allowing
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third parties to effectively use `rustc`'s internals as a library for
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analyzing a crate or emulating the compiler in-process (e.g. rustdoc).
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For those using `rustc` as a library, the [`rustc_interface::run_compiler()`][i_rc]
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function is the main entrypoint to the compiler. It takes a configuration for the compiler
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and a closure that takes a [`Compiler`]. `run_compiler` creates a `Compiler` from the
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configuration and passes it to the closure. Inside the closure, you can use the `Compiler`
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to drive queries to compile a crate and get the results. This is what the `rustc_driver` does too.
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You can see a minimal example of how to use `rustc_interface` [here][example].
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You can see what queries are currently available through the rustdocs for [`Compiler`].
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You can see an example of how to use them by looking at the `rustc_driver` implementation,
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specifically the [`rustc_driver::run_compiler` function][rd_rc] (not to be confused with
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[`rustc_interface::run_compiler`][i_rc]). The `rustc_driver::run_compiler` function
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takes a bunch of command-line args and some other configurations and
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drives the compilation to completion.
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`rustc_driver::run_compiler` also takes a [`Callbacks`][cb],
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a trait that allows for custom compiler configuration,
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as well as allowing some custom code run after different phases of the compilation.
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> **Warning:** By its very nature, the internal compiler APIs are always going
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> to be unstable. That said, we do try not to break things unnecessarily.
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[cb]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/trait.Callbacks.html
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[rd_rc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver_impl/fn.run_compiler.html
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[i_rc]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/interface/fn.run_compiler.html
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[example]: https://github.com/rust-lang/rustc-dev-guide/blob/master/examples/rustc-driver-example.rs
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[`rustc_interface`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/index.html
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[`rustc_driver`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/
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[`Compiler`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_interface/interface/struct.Compiler.html
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[`Session`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_session/struct.Session.html
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[`TyCtxt`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/struct.TyCtxt.html
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[`SourceMap`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_span/source_map/struct.SourceMap.html
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[stupid-stats]: https://github.com/nrc/stupid-stats
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[Appendix A]: appendix/stupid-stats.html
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