hotswap 0.1.7

rust-hotswap

A library for hotswapping running code with minimal effort.

Beware that the library is a prototype for now, and it may crash frequently.

Usage

• Using a nightly rust, import the plugin hotswap.
• Annotate the functions you want to hotswap with the #[hotswap] modifier.
• Add #![hotswap_header] to the top of your program.
• Add unsafe { hotswap_start!() } to the entry point of your program, before you call any hotswapped functions.
• Add a dylib build with the same project name and path to your Cargo.toml.

Current Limitations

• Changing hotswapped function signatures WILL result in a segfault.
• Probably many others that I don't know about!

Example

# Cargo.toml

[package]
name = "hotswapdemo"
version = "0.1.0"

[lib]
name = "hotswapdemo"
crate-type = ["dylib"]
path = "src/main.rs"

[dependencies]
hotswap = "*"

// main.rs

#![feature(plugin)]
#![plugin(hotswap)]
#![hotswap_header]

use std::thread::sleep;
use std::time::Duration;

#[hotswap]
fn test(test: i32) -> () {
    println!("Foo: {}", test);
}

fn main() {
    unsafe{ hotswap_start!() }

    let mut i = 1;
    loop {
        test(i);
        i += 1;
        sleep(Duration::from_millis(2000));
    }
}

And that is it!

From there you can

> cargo run
     Running `target/debug/hotswapdemo`
Foo: 1
Foo: 2
Foo: 3

once it is running, you can edit the printing code, e.g.

    println!("Bar: {} :)", test);

and once you recompile the code on another terminal (or on the same one using background)

> cargo build --lib
   Compiling hotswapdemo v0.1.0 [...]
> fg
Foo: 7
Foo: 8
Bar: 9 :)
Bar: 10 :)

the running code will update without restarting the binary or losing state!