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bazel / crubit / 770bcff460c7fa845f16ba84ced618bc61322960
commit770bcff460c7fa845f16ba84ced618bc61322960[log] [tgz]
authorDevin Jeanpierre <jeanpierreda@google.com>Thu Aug 15 10:11:15 2024 -0700
committerCopybara-Service <copybara-worker@google.com>Thu Aug 15 10:12:08 2024 -0700
tree3e2f35ad5e4163c6306742e16bcd918e58856ca1
parente5ab0c243c334d88d64ca96999e51f7cacda8fcd [diff]
Support `-Cpanic=unwind` (on nightly), by just changing documentation.

Crubit is made sound for free by the changes in nightly to abort when panicking through `extern "C"`. These are documented here: https://doc.rust-lang.org/nomicon/ffi.html#ffi-and-unwinding -- however, note that this functionality has not yet hit Rust stable. The documentation change was made too soon, as far as I can tell. Still, this _will_ be the behavior, and when it is, we will be sound.

For `extern "C-unwind"`, I think our docs here were inaccurate, and it's not sound unless the caller enables exceptions. I suspect we should not release this functionality to end-users yet, as it's dangerous. Maybe we should instead default to the sound option of aborting.

We probably shouldn't say the issue of `panic=unwind` support is "solved" until we both remove the `-Cpanic=abort`, and the behavior reaches a stable release of rustc.

PiperOrigin-RevId: 663349913
Change-Id: I1ab8cb1131c038a023fceae123927eb22c1d0a0f
11 files changed
tree: 3e2f35ad5e4163c6306742e16bcd918e58856ca1
  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