Built-in bindings reference

In addition to all the primitive types (i32 <=> int32_t), the following common types may be used in the fields of shared structs and the arguments and returns of extern functions.


name in Rustname in C++restrictions
Stringrust::String
&strrust::Str
&[T]rust::Slice<const T>cannot hold opaque C++ type
&mut [T]rust::Slice<T>cannot hold opaque C++ type
CxxStringstd::stringcannot be passed by value
Box<T>rust::Box<T>cannot hold opaque C++ type
UniquePtr<T>std::unique_ptr<T>cannot hold opaque Rust type
SharedPtr<T>std::shared_ptr<T>cannot hold opaque Rust type
[T; N]std::array<T, N>cannot hold opaque C++ type
Vec<T>rust::Vec<T>cannot hold opaque C++ type
CxxVector<T>std::vector<T>cannot be passed by value, cannot hold opaque Rust type
fn(T, U) -> Vrust::Fn<V(T, U)>only passing from Rust to C++ is implemented so far
Result<T>throw/catchallowed as return type only

The C++ API of the rust namespace is defined by the include/cxx.h file in the CXX GitHub repo. You will need to include this header in your C++ code when working with those types. When using Cargo and the cxx-build crate, the header is made available to you at #include "rust/cxx.h".

The rust namespace additionally provides lowercase type aliases of all the types mentioned in the table, for use in codebases preferring that style. For example rust::String, rust::Vec may alternatively be written rust::string, rust::vec etc.

Pending bindings

The following types are intended to be supported "soon" but are just not implemented yet. I don't expect any of these to be hard to make work but it's a matter of designing a nice API for each in its non-native language.


name in Rustname in C++
BTreeMap<K, V>tbd
HashMap<K, V>tbd
Arc<T>tbd
Option<T>tbd
tbdstd::map<K, V>
tbdstd::unordered_map<K, V>