bug#36447: 27.0.50; New "Unknown keyword" errors

[Stefan Monnier]

>> His patch can/should be made slightly more efficient by only doing the
>> Fcopy_sequence on those hash-tables that are in purespace.
>
> How do we test for that?

With PURE_P?

> I'm not sure how difficult it would be, but we could dump the ->index,
> ->next, ->hash vectors as Qnil (so not include the actual vectors in
> the dump), which would make the dump slightly smaller and give us a
> better test than h->count < 0:

Except that it can't be done at the time of purecopy but only at the
time we do the actual dump because the purecopied hashtable may be used
in-between (which is also why count is kept positive by purecopy and is
only made negative later).

> Slightly contrived problem here: if the single key in a single-entry
> EQ hash is -7, or an expression that happens to have hash value -1,
> pure->hash and pure->next would be EQ after these two lines, and
> updating the hash would corrupt the hash table...

Indeed.  As I said, I think your approach is better, I only included it
for reference and for the comments I had added.


        Stefan