Safety against obtaining function pointers to functions removed by dlclose?

[jgarvin]

A dastardly user could:

• Write a function that returns a function pointer to itself
• Put that function inside a shared library
• dlopen the library
• Call the function
• Store the returned fn
• Call dlclose on the library
• Try to call the fn. Boom?

Does the crate have anything to prevent this? I see the Symbol types that are trying to ensure you only call a function if it's still loaded as long as you are going through them, but it seems like it's possible for users to circumvent by having functions that return function pointers, but I'm still new to Rust and I haven't actually tried coding this up so I could be wrong.