bug#41321: 27.0.91; Emacs aborts due to invalid pseudovector objects

[Paul Eggert]

On 5/29/20 2:43 AM, Pip Cet wrote:
> As I said, the code is tricky (i.e. might contain bugs that can only
> be discovered through extensive testing on 32-bit systems), and it
> complicates what should be generic functions for the rbtree
> implementation, so this is probably a 32-bit optimization that is too
> late because 32-bit systems are no longer that relevant...

At least at first, it may make more sense to keep the red-black trees as-is, and
to look up what appear to be symbol-tagged pointers twice, once as-is (to find
any kind of object) and once offset by '(char *) lispsym - Lisp_Symbol' (to find
only symbols). Although a bit slower, this won't require any changes to the
rbtree code so it's cleaner. We can then time the optimization you have in mind,
to see whether it's worth doing.