| commit | 1b8338f16e902f314d5b930822a421ffd05b6252 | [log] [tgz] |
|---|---|---|
| author | Martin Brænne <mboehme@google.com> | Wed Aug 07 23:58:13 2024 -0700 |
| committer | Copybara-Service <copybara-worker@google.com> | Wed Aug 07 23:59:31 2024 -0700 |
| tree | 2058fc27c17f50804f3f20548159453d9f26dfbc | |
| parent | e6c6287cac9fff24d6e84a7f4ed01fb2180726ad [diff] |
[lifetime_annotations] Fix template arg size mismatch in `ForEachTemplateArgument()`. The newly added test, without the fix, causes the [size check](https://github.com/google/crubit/blob/b196b493ba61ad99c0373b7aa58c5e833e26869e/lifetime_annotations/type_lifetimes.cc#L226) between `template_arg_locs` and `template_args` to fail. This is because the `QualType` overload of `StripAttributes(QualType)` used to use `Type::getAs<>`, which looks through sugar, while the `TypeLoc` overload uses `TypeLoc::getAs<>`, which doesn't look through sugar. In the case of the newly added test, the `QualType` overload of `StripAttributes()` would look through the `Nullable` alias to find the `_Nullable` attribute and would hence also strip off the `Nullable` alias, while the `TypeLoc` overload would not see the `_Nullable` attribute and would therefore also leave the `Nullable` alias in place. This would then cause the size mismatch because the `QualType` no longer had any template arguments while the `TypeLoc` did. The behavior we want is "don't look through sugar" because we want the template arguments to be preserved so that the call to `ForEachTemplateArgument()` sees them. We achieve this by replacing the `Type::getAs<>()` call in the `QualType` overload with a `dyn_cast<>()`. PiperOrigin-RevId: 660707233 Change-Id: Id95ab7d4a8221bb473732723db1ff89dd5316aee
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.
Support for calling FFI-friendly C++ from Rust is in progress.
Support for calling Rust from C++ will arrive in 2024H2.
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.
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.
$ 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
$ 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