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 #![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.
• Requires an extra dependency in the user application.
• Leaks a dynamic library on each swap.
• Probably many others that I don't know about!

Example

```toml

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 ```

```rust // 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. rust 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!