Comment 2 for bug 1903413

I wondered what would break if we added weakness to the hash tables instantiated in these two places:

https://github.com/sbcl/sbcl/blob/8a2df46b46e3feb201c7f19096018a3f4b1c7d8a/src/code/class.lisp#L290-L292

https://github.com/sbcl/sbcl/blob/532b885acb3da5bf927b600f05d568507075ae3c/src/pcl/std-class.lisp#L186-L188

And built SBCL with with :WEAKNESS :KEY-AND-VALUE in both hash tables.

The change does not seem to break anything, the resulting hash tables have :WEAKNESS :KEY-AND-VALUE, but it does not fix the issue either: the classoids in question are still not purged from the system.

This is likely because the classoids (or references to them) are allocated in static space (at least this is how I interpret the results given to me by SEARCH-ROOTS) and therefore the classoids are not collectable by the GC, which means that simple hash table weakness is not enough to remove them.