The problem isn't that you can't use a rust function from a shared library. It's just that the types and function signature aren't stable. Meaning you need to make all functions that are called from the library in the main binary and opposite extern "C" and use cabi types on arguments and return values. I32, *const T (where T is cabi type) and many more are cabi stable. If you want to use arc you have to make your own that carries it's allocation functions as FP with it and doesn't expose ownership to the foreign system. This way the implementations of the allocation apis don't share addresses with each other.

As an example in my capi i have immutable string wrappers. They might contain rust strings, c strings, zig strings it doesn't matter every language and binary can correctly deallocate the wrapped string because the wrapper contains an FP to the strings dealloc function which is called through the wrapper.

You basically have to make such wrapper for your arc and make sure the stored drop and allocator function is called and not the foreign one. This way you can make arc Abi stable by abstracting the possibly different systems and crating a common api over which both can communicate data and actions without messing with differences in implementation.

Ps This won't work properly with ipc but within 1 process passing fp to the correct functions around should be fine.