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bazel / crubit / e9d8361f51ad466b9c777d1f05c8884ccdef1f89
commite9d8361f51ad466b9c777d1f05c8884ccdef1f89[log] [tgz]
authorDevin Jeanpierre <jeanpierreda@google.com>Fri Jun 28 15:08:41 2024 -0700
committerCopybara-Service <copybara-worker@google.com>Fri Jun 28 15:09:28 2024 -0700
treecf087f71391a9d872861d18347a78c8eeb219cf1
parent5a5099c7fa6a5463c5bb74ce34a18648fed23b45 [diff]
Use standard variadic macros instead of the GNU extension in `CRUBIT_OFFSETOF`.

Right now, we seem to use `CRUBIT_OFFSETOF` from generated files and then build them with the flags from the target the bindings are for, which is probably wrong. This surfaces as parsing failures, when they enable additional warnings. In this case, the warning is correct, I think: we should use the standard va_args mechanism, not a GNU preprocessor extension.

This is one of multiple errors that surface in b/348557947, but doesn't really fix the root cause of that bug, or even of this compilation error. Still, it's an improvement anyway.

PiperOrigin-RevId: 647809127
Change-Id: I31673d34b5b262ab5d65f0202b9a453be0a98f08
1 file changed
tree: cf087f71391a9d872861d18347a78c8eeb219cf1
  1. .bazelci/
  2. bazel/
  3. cc_bindings_from_rs/
  4. common/
  5. docs/
  6. examples/
  7. features/
  8. lifetime_analysis/
  9. lifetime_annotations/
  10. migrator/
  11. nullability/
  12. rs_bindings_from_cc/
  13. support/
  14. .bazelrc
  15. .gitignore
  16. BUILD
  17. Cargo.lock
  18. CODE_OF_CONDUCT
  19. CONTRIBUTING
  20. LICENSE
  21. MODULE.bazel
  22. README.md
  23. WORKSPACE.bzlmod
README.md

Crubit: C++/Rust Bidirectional Interop Tool

Build status

NOTE: Crubit currently expects deep integration with the build system, and is difficult to deploy to environments dissimilar to Google's monorepo. We do not have our tooling set up to accept external contributions at this time.

Crubit is a bidirectional bindings generator for C++ and Rust, with the goal of integrating the C++ and Rust ecosystems.

Status

Support for calling FFI-friendly C++ from Rust is in progress.

Support for calling Rust from C++ will arrive in 2024H2.

Example

Consider the following C++ function:

extern "C" bool IsGreater(int lhs, int rhs);

This function, if present in a header file which is processed by Crubit, becomes callable from Rust as if it were defined as:

pub fn IsGreater(lhs: ffi::c_int, rhs: ffi::c_int) -> bool {...}

Note: There are some temporary restrictions on the API shape. For example, functions that are not extern "C", or that accept a type like std::string, can't be called from Rust directly via Crubit. These restrictions will be relaxed over time.

Getting Started

Here are some resources for getting started with Crubit:

  • Rust Bindings for C++ Libraries is a detailed walkthrough on how to use C++ from Rust using Crubit.

  • The examples/cpp/ directory has copy-pastable examples of calling C++ from Rust, together with snapshots of what the generated Rust interface looks like.

Building Crubit

$ apt install clang lld bazel
$ git clone git@github.com:google/crubit.git
$ cd crubit
$ bazel build --linkopt=-fuse-ld=/usr/bin/ld.lld //rs_bindings_from_cc:rs_bindings_from_cc_impl

Using a prebuilt LLVM tree

$ git clone https://github.com/llvm/llvm-project
$ cd llvm-project
$ CC=clang CXX=clang++ cmake -S llvm -B build -DLLVM_ENABLE_PROJECTS='clang' -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=install
$ cmake --build build -j
$ # wait...
$ cmake --install build
$ cd ../crubit
$ LLVM_INSTALL_PATH=../llvm-project/install bazel build //rs_bindings_from_cc:rs_bindings_from_cc_impl