Re: trunk r113947: * image.c: Fix animation cache signature memory leak.

[Paul Eggert <eggert@cs.ucla.edu>]

Lars Magne Ingebrigtsen wrote:
> Or am I misreading this completely?

No, you got it right.  I expect that I ran the wrong
executable when I thought I was testing the new code.

My code should have looked like the following, I expect.
The advantage of doing it this way is that it calls
imagemagick_create_cache in just one place, and strcmp
in just one place, and refers to 'animation_cache' in
just one place, and updates cache->update time in just
one place, and overall (to my mind anyway) is easier to
understand than the duplications in the current code.
But it's only a minor improvement.

static struct animation_cache *
imagemagick_get_animation_cache (MagickWand *wand)
{
  char *signature = MagickGetImageSignature (wand);
  struct animation_cache **pcache = &animation_cache;

  imagemagick_prune_animation_cache ();

  while (1)
    {
      struct animation_cache *cache = *pcache;
      if (! cache)
	{
          *pcache = cache = imagemagick_create_cache (signature);
          break;
        }
      if (strcmp (signature, cache->signature) == 0)
	{
          DestroyString (signature);
          break;
        }
      pcache = &cache->next;
    }

  cache->update_time = current_emacs_time ();
  return cache;
}

By the way, did you know that each animation signature
contains 4 KiB of wasted memory?  It's ImageMagick
code that's wasting it.  Dunno if that's worth tuning.