Interoperability
Interoperability between Rust and C code is always dependent
on transforming data between the two languages.
For this purpose, there is a dedicated module
in the stdlib called
std::ffi.
std::ffi provides type definitions for C primitive types,
such as char, int, and long.
It also provides some utility for converting more complex
types such as strings, mapping both &str and String
to C types that are easier and safer to handle.
As of Rust 1.30,
functionalities of std::ffi are available
in either core::ffi or alloc::ffi
depending on whether or not memory allocation is involved.
The cty crate and the cstr_core crate
also offer similar functionalities.
| Rust type | Intermediate | C type |
|---|---|---|
String | CString | char * |
&str | CStr | const char * |
() | c_void | void |
u32 or u64 | c_uint | unsigned int |
| etc | ... | ... |
A value of a C primitive type can be used
as one of the corresponding Rust type and vice versa,
since the former is simply a type alias of the latter.
For example, the following code compiles on platforms
where unsigned int is 32-bit long.
fn foo(num: u32) {
let c_num: c_uint = num;
let r_num: u32 = c_num;
}
Interoperability with other build systems
A common requirement for including Rust in your embedded project is combining Cargo with your existing build system, such as make or cmake.
We are collecting examples and use cases for this on our issue tracker in issue #61.
Interoperability with RTOSs
Integrating Rust with an RTOS such as FreeRTOS or ChibiOS is still a work in progress; especially calling RTOS functions from Rust can be tricky.
We are collecting examples and use cases for this on our issue tracker in issue #62.