dynamic_reload | Dynamic reloading of shared libraries

How to store a reference without having to deal with lifetimes?

The answer in 98% of the cases is: you don't. Lifetimes are one of the biggest reasons to use Rust. Lifetimes enforce, at compile time, that your references will always refer to something that is valid. If you wish to "ignore" lifetimes, then perhaps Rust may not the best language to realize a particular design. You may need to pick a different language or design.

Is it a valid workaround to use std::mem::transmute to change Symbol's lifetime to 'static?

transmute is The Big Hammer, suitable for all sorts of good and bad ideas and implementations. I would encourage never using it directly, but instead wrapping it in a layer of abstraction that somehow helps you enforce the appropriate restrictions that make that particular transmute correct.

If you choose to use transmute, you are assuming the full responsibility that the compiler previously had. It will be up to you to ensure that the reference is always valid, otherwise you are invoking undefined behavior and your program is allowed to do any number of Very Bad things.

For your specific case, you may be able to use the Rental crate to keep around "the library" and "references into the library" in a single struct that hides the lifetimes of the Symbols. In fact, Rental uses libloading as the motivating example and libloading powers dynamic_reload. See Why can't I store a value and a reference to that value in the same struct? for more details and pitfalls.

I'm not optimistic that this will work because DynamicReload::update requires a &mut self. During that method call, it could easily invalidate all of the existing references.

See also:

• Why can't I store a value and a reference to that value in the same struct?
• How can I avoid a ripple effect from changing a concrete struct to generic?