In CLOS, instance remorphing considered useless in practice?

[Jean-Claude Beaudoin]

On Wed, Dec 9, 2020 at 3:59 AM Alessio Stalla <alessiostalla at gmail.com>
wrote:

> About multithreading, *all *kinds of redefinition have an impact. If I
> redefine a widely-used, low-level function, with hundreds of call sites –
> will each thread immediately call the new one without the bug, or will some
> still call the old one? Again, imposing a proper order would require
> protecting each function call with a lock, which is even worse for
> performance than protecting each slot access.
>

Isn't "inline/not-inline" doing just what is needed in that area?

Still, we consider function redefinition a key feature of Common Lisp. So,
> redefinition of classes is in accordance with the spirit of the language.
>

Redefinition of function is not "in situ". Why should redefinition of
classes have to be so? I am not advocating against class redefinition!

Anecdotally, implementations that don't allow to redefine what Common Lisp
> doesn't mandate (e.g., in ABCL you cannot really redefine packages), in
> certain situations are painful to use, as they force you to delete &
> recreate everything, possibly even quitting Lisp and restarting.
>
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