Comment by Sesse__

> Serializable in principle, maybe. Actually serializable in the sense that the code contains a way to dump to a file and back, absolutely not. It's extremely rare for programs to expose a way to save and restore from a mid-state in the algorithm they're implementing.

If you should ever look for an actual example; Cubemap, my video reflector (https://manpages.debian.org/testing/cubemap/cubemap.1.en.htm...), works like that. It supports both config change and binary upgrade by serializing its entire state down to a file and then re-execing itself.

It's very satisfying; you can have long-running HTTP connections and upgrade everything mid-flight without a hitch (serialization, exec and deserialization typically takes 20–30 ms or so). But it means that I can hardly use any libraries at all; I have to use a library for TLS setup (the actual bytes are sent through kTLS, but someone needs to do the asymmetric crypto and I'm not stupid enough to do that myself), but it was a pain to find one that could serialize its state. TLSe, which I use, does, but not if you're at certain points in the middle of the key exchange.

So yes, it's extremely rare.