[Freeciv-Dev] Re: [FreeCiv-Cvs] per: Abort possibly infinite loop in ai_unit_rampage...

["Per I. Mathisen" <per@xxxxxxxxxxx>]

On Sun, 8 Dec 2002 freeciv@xxxxxxxxxxxxxxxxxxx wrote:
> Abort possibly infinite loop in ai_unit_rampage() when we are unable to
> move or attack our target.
>
> Patch by Jordi Negrevernis i Font <jorneg@xxxxxxxxxxx> with changes by
> me.

Ooops. Investigating this more properly, I realize that this will give a
number of false positives because we can railroad into empty cities (no
movement spent).

Still, a way to identify and break potential infinite loops in
ai_unit_rampage() is sorely needed. Suggestion pasted below.

In any case, the proper fix for the current infinite loops is pasted
below. Will be committed.

  - Per

Index: ai/aitools.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/ai/aitools.c,v
retrieving revision 1.64
diff -u -r1.64 aitools.c
--- ai/aitools.c        8 Dec 2002 23:42:37 -0000       1.64
+++ ai/aitools.c        9 Dec 2002 01:43:51 -0000
@@ -279,6 +279,10 @@
   pmove.x = x;
   pmove.y = y;
   pmove.unid = punit->id;
+  if (punit->activity != ACTIVITY_IDLE
+      && punit->activity != ACTIVITY_GOTO) {
+    handle_unit_activity_request(punit, ACTIVITY_IDLE);
+  }
   handle_move_unit(unit_owner(punit), &pmove);

   if (find_unit_by_id(sanity) && same_pos(x, y, punit->x, punit->y)) {

Index: ai/aiunit.c
===================================================================
RCS file: /home/freeciv/CVS/freeciv/ai/aiunit.c,v
retrieving revision 1.235
diff -u -r1.235 aiunit.c
--- ai/aiunit.c 9 Dec 2002 00:32:12 -0000       1.235
+++ ai/aiunit.c 9 Dec 2002 01:46:59 -0000
@@ -1057,20 +1057,14 @@

**************************************************************************/
 static struct unit *ai_military_rampage(struct unit *punit, int
threshold)
 {
-  int x, y, moves_left, id = punit->id;
+  int x, y, id = punit->id;
+  int count = punit->moves_left + 1; /* break any infinite loops */

-  while (punit && punit->moves_left > 0
+  while (punit && punit->moves_left > 0 && count-- > 0
          && ai_military_findvictim(punit, &x, &y) >= threshold) {
     moves_left = punit->moves_left;
     ai_unit_attack(punit, x, y);
     punit = find_unit_by_id(id);
-    if (punit) {
-      if (moves_left == punit->moves_left) {
-        /* We were unable to move - avoid infinite loop! */
-        UNIT_LOG(LOG_ERROR, punit, "Unable to move/attack at (%d, %d)", x, y);
-        return punit;
-      }
-    }
   }
   return punit;
 }