Re: undo-tree problem after updates

>> I think this has to do with the fact to `foo.elc` was compiled with an
>> Emacs using an other version of the `define-globalized-minor-mode`
>> macro than the one used when building `foo.eln`.
> This shouldn't be possible, since we explicitly run the exact same
> Emacs binary to perform JIT compilation.

I think you're making assumptions.  In the OP's case, the relevant
package is `undo-tree.el` which is not part of Emacs and I strongly
suspect that they didn't re-byte-compile `undo-tree.el` at the same time
as they upgraded their Emacs.  So I strongly suspect that
`undo-tree.elc` was generated by Emacs<31.


=== Stefan