bug#24634: 25.1 on Windows (native and cygwin+w32): high CPU load with "wavy" characters

[Eli Zaretskii]

> From: Georges Ko <gko@gko.net>
> Date: Sat, 08 Oct 2016 22:11:47 +0800
> 
> When compiled with compact_font_caches empty or not called, Emacs
> crashes at launch...

Sorry, I failed to mention that you need to leave the mark_object call
there.  IOW, the function compact_font_caches should be like this:

static void
compact_font_caches (void)
{
  struct terminal *t;

  for (t = terminal_list; t; t = t->next_terminal)
    {
      Lisp_Object cache = TERMINAL_FONT_CACHE (t);
      mark_object (cache);
    }
}