Allowing to get (relatively) easy C bindings is a goal and feature of rust, at least the project itself provides and maintains the rust-bindgen crate[3][4].
Having a bit bigger and slightly complex project like a backup server done in rust is such a relief compared to C or similar languages. Good speed, fast start up times like C but refactoring is really a breeze lots of safety is guaranteed and more time can be spent on fixing the semantic bugs.
[0]: https://pbs.proxmox.com/docs/introduction.html#introduction
[1]: https://git.proxmox.com/?p=proxmox-backup-qemu.git;a=summary
[2]: https://git.proxmox.com/?p=pve-qemu.git;a=blob;f=debian/patc...