cpp-call-rust

Demonstrates calling Rust functions from C++. Roughly following: http://bitboom.github.io/calling-rust-from-cpp

Why Not Just a Gist?

That's my initial plan since I really don't want to make things more complicated than they should be. But I did because a project I am working on requires C++ code to call Rust code and the C++ side is using Meson. I am new to both Meson and C++ so the gist would focus a lot on those. If I had to do so much documentation, may be it would be easier to just include the entire Rust and C++ code.

Rust Side

1. Each function that you want to expose to C++ will need #[no_mangle] attribute.
2. The same function also need extern "C".
3. The Cargo.toml needs to specify that you are building a C styled shared library: crate-type = ["cdylib"]
4. You also need a header file that includes all signatures of the functions to be exposed to C++. They also need extern "C" so when the C++ code calls, it knows to use C calling convention instead of the C++ one.

C++ Side

1. You need to include the header file for Rust functions wherever you use them.
2. For your meson.build file, there's many ways to let the build system know that you are doing. I used find_library approach. See code for details.

Build Order

I keep it simple:

1. Build Rust side first, producing a .so file (in my case, Linux).
2. Build C++ side (meson.build has information about the .so file and header).