We also need to add a #[no_mangle] annotation to tell the Rust compiler not to mangle the name of this function. Mangling is when a compiler changes the name we’ve given a function to a different name that contains more information for other parts of the compilation process to consume but is less human readable. Every programming language compiler mangles names slightly differently, so for a Rust function to be nameable by other languages, we must disable the Rust compiler’s name mangling.
In the following example, we make the call_from_c function accessible from C code, after it’s compiled to a shared library and linked from C:
#![allow(unused)]
fn main() {
#[no_mangle]
pub extern "C" fn call_from_c() {
println!("Just called a Rust function from C!");
}
}