How to "extern" a function in multiple modules with the same name?

Question

I have a lib project with multiple modules called one and two, in separate files. Each module has a function called run:

mod one {
    pub fn run() {
        println!("One");
    }
}

mod two {
    pub fn run() {
        println!("Two");
    }
}

fn main() {
    one::run();
    two::run();
}

Playground

I would like to compile each of these files/functions to WebAssembly and then be able to load them and call the function run().

I believe I have to add the #[no_mangle] directive and mark them as extern "C" functions. When I do that, then there is a name clash on the run function, despite the module structure.

This is the modified version that won't compile:

mod one {
    #[no_mangle]
    pub extern "C" fn run() {
        println!("One");
    }
}

mod two {
    #[no_mangle]
    pub extern "C" fn run() {
        println!("Two");
    }
}

fn main() {
    one::run();
    two::run();
}

Playground

Is there a way to have multiple modules in a project, each with a function with the same name, such that I can compile the files with the function to WebAssembly, preserving the function name?

Answer 1

No, you cannot give multiple things the same name in a global namespace. That's kind of the definition of what a name and a namespace is. You will need to export them as two different names.

I prefer to have a single location that exports things so it's easier to see and prevent clashes. Additionally, your symbols should be unique among all libraries that will ever be linked with your library. That's why most high-quality C projects use the library name in every single public method.

mod one {
    pub fn run() {
        println!("One");
    }
}

mod two {
    pub fn run() {
        println!("Two");
    }
}

#[no_mangle]
pub extern "C" fn mylib_one_run() {
    one::run()
}

#[no_mangle]
pub extern "C" fn mylib_two_run() {
    two::run()
}

fn main() {
    one::run();
    two::run();
}

See also:

• How do I apply a macro attribute to a function defined in a separate module?