Can rust library be used from another languages in a way c libraries do?

Question

Writing such library will I have to sacrifice std? How, for example, will do I write python bindings to rust library, if possible?

Answer 1

First, indicate to Rust that you want to create a function visible to C:

#[no_mangle]
pub extern "C" fn some_func() { ... }

This tells Rust to avoid mangling the output symbol and to use the C ABI.

Next, you will need to use C-compatible types when crossing the boundary. Here is some advice that has worked for me:

• If you are planning to pass a Rust structure to C as opaque data, which it will pass back into other functions, return it as a Box<T>, and take it as a &T or Box<T>. Essentially, this means that you are giving up ownership of the structure in Rust, and giving ownership to the C code. The C code must ensure that if it passes the pointer back into a function that takes a Box, it no longer uses it.
• If you are planning to pass a Rust structure to C as a C structure, Rust conveniently represents its structs in a C-compatible way. However, you will want to restrict the kinds of values you put in these structs to types that also have compatible C representations. Numeric types and booleans are safe, of course.
• You can see the Rust representation of more complex types (like vecs and strings) in the docs under core::raw. A &str and &[T] are represented as raw::Slice while a Vec<T> is represented as a raw::Vec.
• You can also convert types into the libc::types
• Finally, you may find yourself needing to work with pointers directly. Check out std::mem for useful APIs.