bug#29220: 26.0.90; eieio-persistent-read fail to restore saved object.

[Noam Postavsky <npostavs@users.sourceforge.net>]

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> (Are you guys looking at a different version of the pcache repo? The one
> on Github uses `constructor', not `make-instance'.)

The version mentioned in #23:

    I've put an branch (pte/emacs-26) on github
    (https://github.com/PierreTechoueyres/pcache.git) with some tests that
    you can launch with

> The call to `eieio-persistent-read' does basic slot value validation,
> but this function is additionally checking that all of the entries in
> the hash table are of the proper class, that specified in the
> `entry-cls' slot.
>
> But I still think the problem isn't in reading, it's in writing: the
> entries in the hash table are being written incorrectly, and so this
> validation step is exploding.

Yes, the way structs and classes are encoded in emacs-26 changed, so the
way they're written changed also.  It seems the round-tripping loses the
class/type maybe?  I can still see the '44' entry in the hash table, so
the hash table itself is still in there...

> I sure don't know why setting `print-circle' to t would have solved it,
> though...

Setting print-circle only lets the read work without error, the read
object still fails the pcache validation.