Re: MPS: dangling markers

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

Pip Cet <pipcet@protonmail.com> writes:

>> True. I forgot to mention an important thing: When something is splat,
>> set flag(s) in the dependent hash table indicating that something must
>> be done because of that splatting. In gethash and so, check the flag and
>> do what's necessary. (I did something similar for the weak hash tables
>> in CMUCL, and it wasn't entirely bad. And weak tables should be rare.)
>
> Not necessarily rare, particularly not if we turn BUF_MARKERS into a
> weak hash table (I still don't see why we shouldn't do that, maybe I
> missed it).

Hm, don't know. On the one hand, there's Stefan's gap buffer data
structure, and on the other hand add_marker and remove_marker are now
O(1) in igc, modulo bugs. So the pressure has decreased.

>
> But, yes, that's a good idea and requires far fewer changes to the
> hash table code than I've now made locally. However, I've decided to
> go through with it and have just successfully splatted my first weak
> hash table entry.

Congrats! :-). I have to say, my ideas are idle musings, that I'll
probably never realize. Working code wins :-).

> If we go with my original proposal (which I'm not at all sure about at
> this point as the code is really ugly), we'd have to have something
> like:
>
> struct Lisp_Weak_Hash_Table
> {
>   union vectorlike_header header;
>
>   struct Lisp_Weak_Hash_Table_Strong_Part *strong;
>   struct Lisp_Weak_Hash_Table_Weak_Part *weak;
> };

Thanks, I think I got it now. I lost context.