hotswap 0.1.2

rust-hotswap

A library for hotswapping running code with minimal effort.

Beware that the library is a completely unsafe prototype for now, and it will probably crash a lot.

Usage

• Using a nightly rust, import the plugin hotswap.
• Annotate the functions you want to hotswap with the #[hotswap] modifier.
• Add the #![hotswap_header] to the top of your program.
• Add the hotswap_start!() macro to the entry point of your program, before you call any hotswapped functions.

Current Limitations

• Changing hotswapped function signatures WILL result in a segfault.
• Requires extra dependency in the user application.
• Leaks a dynamic library on each swap.

Example

# Cargo.toml

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

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

[dependencies]
hotswap = "*"    # libloading is a required
libloading = "*" # dependency for now

// 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() {
    hotswap_start!();

    loop {
        test(123);
        sleep(Duration::from_millis(2000));
    }
}

And that is it! From there you can

> cargo run
     Running `target\debug\hotswaptest.exe`
Foo: 123
Foo: 123
Foo: 123

and if you edit the printing code, changing it to

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

and recompiling the code on another terminal (or putting the running task in the background)

> cargo build --lib
   Compiling hotswapdemo v0.1.0[...]
> fg
Foo: 123
Foo: 123
Bar: 123
Bar: 123

the running function will update automatically to the latest version without restarting the executable!