Re: MPS: weak hash tables

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

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Gerd Möllmann <gerd.moellmann@gmail.com>
>> Cc: pipcet@protonmail.com,  eller.helmut@gmail.com,  yantar92@posteo.net,
>>   emacs-devel@gnu.org
>> Date: Sun, 07 Jul 2024 20:15:34 +0200
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> > I understand all that, but unchaining an interval involves the need to
>> > modify the pointers of its adjacent nodes, and how can MPS do that
>> > without understanding our data structures?
>> 
>> Can you please show me what code you mean? 
>
> This one:
>
>   static void
>   sweep_intervals (void)
>   {
>     struct interval_block **iprev = &interval_block;
>     int lim = interval_block_index;
>     object_ct num_free = 0, num_used = 0;
>
>     interval_free_list = 0;
>
>     for (struct interval_block *iblk; (iblk = *iprev); )
>       {
> 	int this_free = 0;
> 	ASAN_UNPOISON_INTERVAL_BLOCK (iblk);
> 	for (int i = 0; i < lim; i++)
> 	  {
> 	    if (!iblk->intervals[i].gcmarkbit)
> 	      {
> 		set_interval_parent (&iblk->intervals[i], interval_free_list);
> 		interval_free_list = &iblk->intervals[i];
> 		ASAN_POISON_INTERVAL (&iblk->intervals[i]);
> 		this_free++;
> 	      }
> 	    else
> 	      {
> 		num_used++;
> 		iblk->intervals[i].gcmarkbit = 0;
> 	      }
> 	  }
> 	lim = INTERVAL_BLOCK_SIZE;
> 	/* If this block contains only free intervals and we have already
> 	   seen more than two blocks worth of free intervals then
> 	   deallocate this block.  */
> 	if (this_free == INTERVAL_BLOCK_SIZE && num_free > INTERVAL_BLOCK_SIZE)
> 	  {
> 	    *iprev = iblk->next;
> 	    /* Unhook from the free list.  */
> 	    ASAN_UNPOISON_INTERVAL (&iblk->intervals[0]);
> 	    interval_free_list = INTERVAL_PARENT (&iblk->intervals[0]);
> 	    lisp_free (iblk);
> 	  }
> 	else
> 	  {
> 	    num_free += this_free;
> 	    iprev = &iblk->next;
> 	  }
>       }

Ah!

There are no interval_blocks, no interval_free_list nothing of that in
MPS.