What exactly is a Rust "toolchain"?

Question

I've seen rustup be referred to as a "toolchain installer", but it's hard to find an exact definition of what Rust considers a "toolchain" to be and what the scope is for the concept.

I already have the Rust compiler and Cargo installed. What more does rustup bring? Is it just a Rust-version-switcher?

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As a .NET-developer, maybe there is there a parallel which makes it easier for me to grasp this concept?

Humperdinck

A terse definition is given in the rustup README.md on Github: _"Many rustup commands deal with toolchains, a single installation of the Rust compiler. rustup supports multiple types of toolchains. The most basic track the official release channels: stable, beta and nightly; but rustup can also install toolchains from the official archives, for alternate host platforms, and from local builds."_I don't know if an exact definition exists, behind the generic notion of a software toolchain – Disinfest

You can run rustup toolchain list which in my case prints stable-x86_64-unknown-linux-gnu (default). So you can think of the toolchain as a specific version of the compiler, the standard library and the accompanying tools such as clippy, cargo, etc – Irreverent

Answer 1

A toolchain is a specific version of the collection of programs needed to compile a Rust application. It includes, but is not limited to:

• The compiler, rustc
• The dependency manager and build tool, cargo
• The documentation generator, rustdoc
• The static and/or dynamic libraries comprising the standard library for the default platform

There are additional components that can be installed, such as

• Documentation
  • The Rust Programming Language
  • The standard library
  • Various books and references
• The static and/or dynamic libraries comprising the standard library for additional platforms to cross-compile to
• The source code for the standard library
• Extra utilities
  • Code formatting via rustfmt
  • Extra lints via clippy
  • Undefined behavior checking via miri
  • Advanced editor support via rust-analyzer or the Rust Language Server

Rustup provides ways to install, remove, update, select and otherwise manage these toolchains and their associated pieces.

See also:

• How to install a Rust target for a specific rustup toolchain?
• How to remove Rust compiler toolchains with Rustup?
• How to switch between rust toolchains
• How do I tell which Windows toolchain my Rust compiler is using?
• How to execute cargo test using the nightly channel?

Judgment

The linker is also part of the toolchain. It's significant enough to include in the list. – Metaphase

@Metaphase can you point me to which platforms rustup installs a linker for? My understanding is that Rust relies on the system linker (which is why you also have to install a C toolchain). – Judgment

That's my understanding too, but @linspectable's point is well taken, even if it's only to explain that this is one part that rustup doesn't handle. Especially since it can get messy when you're cross compiling. – Mousetrap