Detect the overflow for the object ID

Continue to increase the object id even after FcFini()
and detect the overflow. that would be rather easier than
reset the object id with the complicated mutex and atomic
functions.

This situation would be quite unlikely to happen though

src/fcobjs.c

@@ -51,6 +51,8 @@ FcObjectFini (void)
 
 retry:
     ots = fc_atomic_ptr_get (&other_types);
+    if (!ots)
+	return;
     if (!fc_atomic_ptr_cmpexch (&other_types, ots, NULL))
 	goto retry;
 
@@ -68,6 +70,8 @@ static FcObjectType *
 _FcObjectLookupOtherTypeByName (const char *str, FcObject *id)
 {
     struct FcObjectOtherTypeInfo *ots, *ot;
+    static fc_atomic_int_t first_id = 0;
+    static FcBool overflow = FcFalse;
 
 retry:
     ots = fc_atomic_ptr_get (&other_types);
@@ -76,6 +80,11 @@ retry:
 	if (0 == strcmp (ot->object.object, str))
 	    break;
 
+    if (!ots)
+    {
+	first_id = fc_atomic_int_add (next_id, 0);
+	overflow = FcFalse;
+    }
     if (!ot)
     {
 	ot = malloc (sizeof (*ot));
@@ -84,14 +93,25 @@ retry:
 
 	ot->object.object = (char *) FcStrdup (str);
 	ot->object.type = FcTypeUnknown;
+    retry_id:
 	ot->id = fc_atomic_int_add (next_id, +1);
+	if (overflow && ot->id == first_id)
+	{
+	    fprintf (stderr, "Fontconfig error: No object ID to assign\n");
+	    abort ();
+	}
+	if (ot->id < (FC_MAX_BASE_OBJECT + FC_EXT_OBJ_INDEX))
+	{
+	    overflow = FcTrue;
+	    fc_atomic_ptr_cmpexch (&next_id, ot->id + 1, FC_MAX_BASE_OBJECT + FC_EXT_OBJ_INDEX + 1);
+	    goto retry_id;
+	}
 	ot->next = ots;
 
 	if (!fc_atomic_ptr_cmpexch (&other_types, ots, ot)) {
 	    if (ot->object.object)
 		free (ot->object.object);
 	    free (ot);
-	    fc_atomic_int_add (next_id, -1);
 	    goto retry;
 	}
     }