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bazel / crubit / 0d4af603f6207f6a17e28749ebd834d1f8ba49b8
commit0d4af603f6207f6a17e28749ebd834d1f8ba49b8[log] [tgz]
authorYongheng Chen <yongheng@google.com>Fri Oct 04 01:47:26 2024 -0700
committerCopybara-Service <copybara-worker@google.com>Fri Oct 04 01:48:58 2024 -0700
tree4a69baa914ac9417a21905ddc6ac56700aaefb07
parent7fe36ec940673e102f2a8e39f3a9b40d465628f2 [diff]
Rename Crubit generated header name from `target_cc_api.h` to `target.h`.

Currently, `target.h` is just a wrapper of `target_cc_api.h`. Once we replace all the `target_cc_api.h`, it is deprecated and will not be generated any more.

PiperOrigin-RevId: 682223235
Change-Id: I9cec09debba4f6545f556ffbbb368e85c86c5427
1 file changed
tree: 4a69baa914ac9417a21905ddc6ac56700aaefb07
  1. .bazelci/
  2. bazel/
  3. cargo/
  4. cc_bindings_from_rs/
  5. common/
  6. docs/
  7. examples/
  8. features/
  9. lifetime_analysis/
  10. lifetime_annotations/
  11. migrator/
  12. nullability/
  13. rs_bindings_from_cc/
  14. support/
  15. .bazelrc
  16. .gitignore
  17. BUILD
  18. Cargo.lock
  19. Cargo.toml
  20. CODE_OF_CONDUCT
  21. CONTRIBUTING
  22. LICENSE
  23. MODULE.bazel
  24. README.md
  25. 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:

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 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

Cargo

Prerequisites:

  • Requires LLVM and Clang libraries to be built and installed.
    • They must be built with support for compression (zlib), which is the default build config.
  • Requires Abseil libraries to be built and installed.
  • Requires zlib (e.g. libz.so) to be available in the system include and lib paths.
  • An up-to-date stable Rust toolchain.

Linux-specific setup:

# Choice of compiler is optional.
export CC=/path/to/clang
export CXX=/path/to/clang++

# We must use `lld` linker via clang. It must be in the PATH.
export PATH="$PATH:/dir/containing/lld"
export RUSTFLAGS="$RUSTFLAGS -Clinker=/path/to/clang"
export RUSTFLAGS="$RUSTFLAGS -Clink-arg=-fuse-ld=lld"

# If you want to use a sysroot.
# SYSROOT_FLAG=--sysroot=$SYSROOT
# export CXXFLAGS="$CXXFLAGS $SYSROOT_FLAG"
# export RUSTFLAGS="$RUSTFLAGS -Clink-arg=$SYSROOT_FLAG"

MacOS-specific setup:

export CC=clang
export CXX=clang++
export RUSTFLAGS="$RUSTFLAGS -Clinker=clang"
export RUSTFLAGS="$RUSTFLAGS -Clink-arg=-fuse-ld=lld"

# Point to the Xcode sysroot.
export CXXFLAGS="$CXXFLAGS -isysroot $(xcrun --show-sdk-path)"
export RUSTFLAGS="$RUSTFLAGS -Clink-arg=-isysroot -Clink-arg=$(xcrun --show-sdk-path)"

Windows-specific setup:

  • Windows is currently unsupported, and the APIs generated by Crubit may not compile and will change over time.
  • All commands must be run from a development shell, where MSVC environment variables are set up.
# We use clang compiler (clang-cl); MSVC may work too but is unsupported.
export CC=clang-cl
export CXX=clang-cl
# We must use lld to link, which is spelt lld-link. So user-specified linker
# flags must be in MSVC format.
export RUSTFLAGS="$RUSTFLAGS -Clinker=/path/to/lld-link"

# LLVM was built with Zlib support. Point Crubit to the same library.
export CXXFLAGS="$CXXFLAGS /I/path/to/zlib"
export RUSTFLAGS="$RUSTFLAGS -Clink-arg=/LIBPATH:/path/to/zlib"

# Avoid deprecation warnings.
export CXXFLAGS="$CXXFLAGS /D_CRT_SECURE_NO_DEPRECATE"

# If LLVM (-DCMAKE_MSVC_RUNTIME_LIBRARY) and Abseil (-DABSL_MSVC_STATIC_RUNTIME)
# are built against static CRT, then Rust needs to match, or vice-versa.
# export RUSTFLAGS="$RUSTFLAGS -Ctarget-feature=+crt-static"

Run the build step via cargo:

# Paths for Crubit's cargo to use.
## This path contains clang/ and llvm/ dirs with their respective headers.
export CLANG_INCLUDE_PATH=/path/to/llvm/and/clang/headers
## This path contains libLLVM*.a and libclang*.a.
export CLANG_LIB_STATIC_PATH=/path/to/llvm/and/clang/libs
## This path contains absl/ dir with all the includes.
export ABSL_INCLUDE_PATH=/path/to/absl/include/dir
## This path contains libabsl_*
export ABSL_LIB_STATIC_PATH=/path/to/absl/libs

cargo build --bin rs_bindings_from_cc

Bazel

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