Dynamic Rust Library

Hello there! Today I will show you how to make dynamic rust libraries and call functions dynamically!

Create the dynamic library

Initialize a rust library:

$ cargo new dynamic_lib --lib

Edit Cargo.toml:

[package]
name = "dynamic_lib"
version = "0.1.0"
edition = "2021"

[lib]
crate-type=["dylib"]

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]

Write a function

Delete the contents of src/lib.rs.
Edit src/lib.rs:

#[no_mangle]
pub fn add(x: usize, y: usize) -> usize {
    x + y
}

Build

cargo build --release

The library is found in target/release and will be named libdynamic_lib.so, dynamic_lib.dll, or libdynamic_lib.dylib depending on the platform.

Call from rust

We use the libloading crate.
Edit the caller crates Cargo.toml:

[dependencies]
...
libloading = "0.8"

Add this code to call a dynamic function:

unsafe {
    let lib = libloading::Library::new("/home/samuel/Code/Own/Tests/dynamic_lib/target/release/libdynamic_lib.so").unwrap();
    let func: libloading::Symbol<fn(usize, usize) -> usize> = lib.get(b"add").unwrap();
    println!("{}", func(1, 2));
    // output: 3
}