relib is a framework for reloadable dynamic libraries written in Rust.
relib_demo.mp4
Currently Linux has the best support, Windows is supported partially, macOS is not supported (not tested), see support matrix.
relib tries to be a safe (as much as possible) runtime of native, almost normal Rust programs. Programs that can be safely unloaded (without memory leaks and crashes) without closing the whole OS process.
Since it's not possible to make this completely safe: memory leaks, UB can still happen (for example, due to some unsafe call to C library), you should only use unloading for development (see live reload example). relib can also be used without unloading, see "Usage without unloading".
See feature support matrix for what relib offers to improve unloading of dynamic libraries in Rust. And for what not, check out limitations.
See examples.
See docs of relib crate.
Currently, relib doesn't check in runtime that function signatures (arguments, return types) specified in imports and exports traits (main and before_unload as well) are exactly the same for host and module.
To ensure at least something about ABI relib checks and requires that host and module are compiled with the same rustc and relib version.
For ABI stable types, you can use abi_stable or stabby crate for it, see abi_stable usage example.
Currently, relib knows nothing about file descriptors or network sockets (unlike background threads) so, for example, if your program stores them in static items and does not properly close them they will leak after unloading.
note: relib provides before_unload callback API when you need to cleanup something manually (similar to Rust Drop).
If your program deadlocks unloading won't work and you will have to kill the whole process.
If you can you should use WebAssembly since it's much more memory-safe approach. But what if WASM is not enough for you for some of these reasons: (some of which may be resolved in the future)
- you need to communicate with C++ or C
- you want to use all features of Rust (for example, multi threading, panics, backtraces may not be supported really well in WASM ecosystem)
- you've already written something in normal Rust and don't want to rewrite it to work in WASM
- you don't need sandboxing/isolation
- performance
- bugs in WASM runtimes
Awesome fasterthanlime's article ❤️ https://fasterthanli.me/articles/so-you-want-to-live-reload-rust