Linking

Calling C from Rust can look like just writing an extern "C" declaration.

The real issue is different: a C function does not carry Rust’s borrowing, lifetime, Result, or destructor rules. Rust can call it, but the compiler cannot prove that the call satisfies the C API contract.

A better model is:

safe Rust API
-> validate and prepare arguments
-> call C inside a small unsafe block
-> convert error codes, output parameters, and raw pointers back to Rust types

The previous article covered C calling Rust. This one covers the other direction: Rust calling C.