impl Clone where appropriate

[strake]

I'm not sure what your criteria are for what should be Clone and/or Copy, so let me know what you think of it. (I am using the impl for Port in particular.)

[phil-opp]

Thanks for the PR!

I don't think that it's a good idea to implement Copy for all possible types, because it is often not necessary and might hinder us from extending the type later (removing the Copy implementation later would be a breaking change). So I would only implement Copy if there is some reason to do so. I don't see such a reason for the various error structs or the Cr0/Cr3 registers (there's nothing you can do with a Cr0 instance).

Another disadvantage when implementing Copy is that it is possible to accidentally copy something instead of borrowing it, so that instead of modifying the original object, the modification happens on a copy and is lost. Therefore I would refrain from implementing Copy for everything with modifiable inner state (such as GlobalDescriptorTable). Instead, I would only implement Clone, so that the copying is explicit and can't happen accidentally.

So instead of implementing Copy wherever possible, I would only implement it when it's needed and doesn't lead to accidental mistakes. Deriving Clone, PartialEq, and Eq for Port seems fine to me and deriving Clone (but not Copy) for GlobalDescriptorTable, Descriptor, InterruptDescriptorTable, and ExceptionStackFrame seems fine to me too. Are there other Clone/Copy implementations that you need?

[strake]

Makes sense. (The Eq and PartialEq impls slipped in while i was staging the PR, but i do want them.) I mostly need the impls for Port right now, but thought i ought to figure out what else ought to be Clone while i'm at it.

PTAL

[phil-opp]

Thanks for the update! Looks good to me.