Rust for Dreamcast

Creating a Rust library

Next, we'll demonstrate creating a Rust library with kos-cargo that can be included in other Dreamcast code. This will follow the addlib example. Once again, this project's initial setup is done the same as the above hello example, but you'll create the new project using kos-cargo new --lib addlib to specify that we're creating a library named addlib. You'll also need to add the following text to this project's Cargo.toml file:

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

This tells Rust to build a static .a library archive file from our code, which is located in src/lib.rs:

#![allow(unused)]
fn main() {
#[no_mangle]
pub extern "C" fn print_added(a: isize, b: isize) {
    print!("{}", a + b);
}

#[no_mangle]
pub extern "C" fn add_integers(a: isize, b: isize) -> isize {
    a + b
}
}

Two simple functions are provided: one for adding two integers and returning the result, and another for adding two integers and printing the result as text. Because these functions use #[no_mangle] and are declared extern "C", they can be called by name in C code that links this library.

When built using kos-cargo build, a target/sh-elf/debug/libaddlib.a file will be generated. This can be linked into other projects to gain the use of these functions.

For example, this can be added to a standard Makefile-based KallistiOS project by editing the Makefile:

$(TARGET): $(OBJS)
	kos-cc -o $(TARGET) $(OBJS) -L/opt/toolchains/dc/rust/examples/cargo-addlib/target/sh-elf/debug -laddlib

Then, we can use the code in our C source:

/* Declare the external function from the Rust library */
int add_integers(int a, int b);

/* Use the function */
printf("Five plus six is %d\n", add_integers(5, 6));