# Example Bindings

CXX requires that the whole C++/Rust boundary is declared in `cxx::bridge`
modules inside `.rs` source code.

```rust,ignore
{{#include ../../../third_party/cxx/book/snippets.rs:cxx_overview}}
```

<details>

Point out:

* Although this looks like a regular Rust `mod`, the `#[cxx::bridge]`
  procedural macro does complex things to it. The generated code is quite
  a bit more sophisticated - though this does still result in a `mod` called
  `ffi` in your code.
* Native support for C++'s `std::unique_ptr` in Rust
* Native support for Rust slices in C++
* Calls from C++ to Rust, and Rust types (in the top part)
* Calls from Rust to C++, and C++ types (in the bottom part)

**Common misconception**: It _looks_ like a C++ header is being parsed by Rust,
but this is misleading. This header is never interpreted by Rust, but simply
`#include`d in the generated C++ code for the benefit of C++ compilers.

</details>