Where are the actual third_party/crubit/support/... headers?

Chromium clients can include and use Crubit support library through the #include "third_party/crubit/support/... paths:

• Support library examples:
  • #include "third_party/crubit/support/rs_std/option.h
  • #include "third_party/crubit/support/rs_std/slice_ref.h
• Rust standard library bindings examples:
  • #include "third_party/crubit/support/rs_std/rs_core.h"
  • #include "third_party/crubit/support/rs_std/rs_std.h"

These #include paths work, even though Chromium repository root doesn't contain third_party/crubit/support directory. If you are trying to find the actual headers, then you need to look in:

• Crubit sources distributed with the Rust toolchain: third_party/rust-toolchain/lib/third_party/crubit/support/.... (See also include_dirs defined in build/rust/crubit/BUILD.gn.)
• Build-time generated Crubit bindings for the Rust standard library: out/.../gen/third_party/crubit/support/.... (See also how cpp_api_from_rust and h_out attributes are used by build/rust/std/rules/BUILD.gn and build/rust/std/BUILD.gn.hbs).

Enabling #include paths that are unified across Chromium and other Crubit clients (e.g. google3) is desirable, because it promotes code portability and hides details of how Crubit is distributed and integrated into Chromium.

Where is Crubit's BUILD.gn?

Chromium integration of Crubit is provided by //build/rust/*.gni and Crubit's BUILD.gn file lives in //build/rust/crubit/BUILD.gn. Moving the BUILD.gn file to //third_party/crubit/BUILD.gn is undesirable, because it would make it more difficult to use Crubit in projects like PDFium or V8 (these projects already depend on Chromium's //build directory but we want to avoid depending on additional directories).

Where can I find additional information about Crubit?

For more information about using Crubit in Chromium please see //docs/rust/crubit.md.