Fix image cache marking bug (Bug#6301).

* src/alloc.c (mark_terminals): Ensure that the image cache is marked
even if the terminal object was marked earlier (Bug#6301).

src/ChangeLog

+2010-11-22  YAMAMOTO Mitsuharu  <mituharu@math.s.chiba-u.ac.jp>
+
+	* alloc.c (mark_terminals): Ensure that the image cache is marked
+	even if the terminal object was marked earlier (Bug#6301).
+
 2010-11-21  Chong Yidong  <cyd@stupidchicken.com>
 
 	* editfns.c (Fbyte_to_string): Signal an error arg is not a byte.

src/alloc.c

@@ -5771,13 +5771,14 @@ mark_terminals (void)
   for (t = terminal_list; t; t = t->next_terminal)
     {
       eassert (t->name != NULL);
-      if (!VECTOR_MARKED_P (t))
-	{
 #ifdef HAVE_WINDOW_SYSTEM
-	  mark_image_cache (t->image_cache);
+      /* If a terminal object is reachable from a stacpro'ed object,
+	 it might have been marked already.  Make sure the image cache
+	 gets marked.  */
+      mark_image_cache (t->image_cache);
 #endif /* HAVE_WINDOW_SYSTEM */
-	  mark_vectorlike ((struct Lisp_Vector *)t);
-	}
+      if (!VECTOR_MARKED_P (t))
+	mark_vectorlike ((struct Lisp_Vector *)t);
     }
 }