updated for version 7.3.055

Problem:    Recursively nested lists and dictionaries cause a near-endless
            loop when comparing them with a copy. (ZyX)
Solution:   Limit recursiveness in a way that non-recursive structures can
            still be nested very deep.
Files:      src/eval.c, src/testdir/test55.in, src/testdir/test55.ok

src/eval.c

@@ -434,9 +434,9 @@ static listitem_T *listitem_alloc __ARGS((void));
 static void listitem_free __ARGS((listitem_T *item));
 static void listitem_remove __ARGS((list_T *l, listitem_T *item));
 static long list_len __ARGS((list_T *l));
-static int list_equal __ARGS((list_T *l1, list_T *l2, int ic));
+static int list_equal __ARGS((list_T *l1, list_T *l2, int ic, int recursive));
-static int dict_equal __ARGS((dict_T *d1, dict_T *d2, int ic));
+static int dict_equal __ARGS((dict_T *d1, dict_T *d2, int ic, int recursive));
-static int tv_equal __ARGS((typval_T *tv1, typval_T *tv2, int ic));
+static int tv_equal __ARGS((typval_T *tv1, typval_T *tv2, int ic, int recursive));
 static listitem_T *list_find __ARGS((list_T *l, long n));
 static long list_find_nr __ARGS((list_T *l, long idx, int *errorp));
 static long list_idx_of_item __ARGS((list_T *l, listitem_T *item));
@@ -4350,7 +4350,8 @@ eval4(arg, rettv, evaluate)
 		else
 		{
 		    /* Compare two Lists for being equal or unequal. */
-		    n1 = list_equal(rettv->vval.v_list, var2.vval.v_list, ic);
+		    n1 = list_equal(rettv->vval.v_list, var2.vval.v_list,
+								   ic, FALSE);
 		    if (type == TYPE_NEQUAL)
 			n1 = !n1;
 		}
@@ -4379,7 +4380,8 @@ eval4(arg, rettv, evaluate)
 		else
 		{
 		    /* Compare two Dictionaries for being equal or unequal. */
-		    n1 = dict_equal(rettv->vval.v_dict, var2.vval.v_dict, ic);
+		    n1 = dict_equal(rettv->vval.v_dict, var2.vval.v_dict,
+								   ic, FALSE);
 		    if (type == TYPE_NEQUAL)
 			n1 = !n1;
 		}
@@ -5914,10 +5916,11 @@ list_len(l)
  * Return TRUE when two lists have exactly the same values.
  */
     static int
-list_equal(l1, l2, ic)
+list_equal(l1, l2, ic, recursive)
     list_T	*l1;
     list_T	*l2;
     int		ic;	/* ignore case for strings */
+    int		recursive;  /* TRUE when used recursively */
 {
     listitem_T	*item1, *item2;
 
@@ -5931,7 +5934,7 @@ list_equal(l1, l2, ic)
     for (item1 = l1->lv_first, item2 = l2->lv_first;
 	    item1 != NULL && item2 != NULL;
 			       item1 = item1->li_next, item2 = item2->li_next)
-	if (!tv_equal(&item1->li_tv, &item2->li_tv, ic))
+	if (!tv_equal(&item1->li_tv, &item2->li_tv, ic, recursive))
 	    return FALSE;
     return item1 == NULL && item2 == NULL;
 }
@@ -5953,10 +5956,11 @@ dict_lookup(hi)
  * Return TRUE when two dictionaries have exactly the same key/values.
  */
     static int
-dict_equal(d1, d2, ic)
+dict_equal(d1, d2, ic, recursive)
     dict_T	*d1;
     dict_T	*d2;
     int		ic;	/* ignore case for strings */
+    int		recursive; /* TRUE when used recursively */
 {
     hashitem_T	*hi;
     dictitem_T	*item2;
@@ -5977,7 +5981,7 @@ dict_equal(d1, d2, ic)
 	    item2 = dict_find(d2, hi->hi_key, -1);
 	    if (item2 == NULL)
 		return FALSE;
-	    if (!tv_equal(&HI2DI(hi)->di_tv, &item2->di_tv, ic))
+	    if (!tv_equal(&HI2DI(hi)->di_tv, &item2->di_tv, ic, recursive))
 		return FALSE;
 	    --todo;
 	}
@@ -5985,41 +5989,54 @@ dict_equal(d1, d2, ic)
     return TRUE;
 }
 
+static int tv_equal_recurse_limit;
+
 /*
  * Return TRUE if "tv1" and "tv2" have the same value.
  * Compares the items just like "==" would compare them, but strings and
  * numbers are different.  Floats and numbers are also different.
  */
     static int
-tv_equal(tv1, tv2, ic)
+tv_equal(tv1, tv2, ic, recursive)
     typval_T *tv1;
     typval_T *tv2;
     int	     ic;	    /* ignore case */
+    int	     recursive;	    /* TRUE when used recursively */
 {
     char_u	buf1[NUMBUFLEN], buf2[NUMBUFLEN];
     char_u	*s1, *s2;
-    static int  recursive = 0;	    /* cach recursive loops */
+    static int  recursive_cnt = 0;	    /* catch recursive loops */
     int		r;
 
     if (tv1->v_type != tv2->v_type)
 	return FALSE;
+
     /* Catch lists and dicts that have an endless loop by limiting
-     * recursiveness to 1000.  We guess they are equal then. */
+     * recursiveness to a limit.  We guess they are equal then.
-    if (recursive >= 1000)
+     * A fixed limit has the problem of still taking an awful long time.
+     * Reduce the limit every time running into it. That should work fine for
+     * deeply linked structures that are not recursively linked and catch
+     * recursiveness quickly. */
+    if (!recursive)
+	tv_equal_recurse_limit = 1000;
+    if (recursive_cnt >= tv_equal_recurse_limit)
+    {
+	--tv_equal_recurse_limit;
 	return TRUE;
+    }
 
     switch (tv1->v_type)
     {
 	case VAR_LIST:
-	    ++recursive;
+	    ++recursive_cnt;
-	    r = list_equal(tv1->vval.v_list, tv2->vval.v_list, ic);
+	    r = list_equal(tv1->vval.v_list, tv2->vval.v_list, ic, TRUE);
-	    --recursive;
+	    --recursive_cnt;
 	    return r;
 
 	case VAR_DICT:
-	    ++recursive;
+	    ++recursive_cnt;
-	    r = dict_equal(tv1->vval.v_dict, tv2->vval.v_dict, ic);
+	    r = dict_equal(tv1->vval.v_dict, tv2->vval.v_dict, ic, TRUE);
-	    --recursive;
+	    --recursive_cnt;
 	    return r;
 
 	case VAR_FUNC:
@@ -9391,7 +9408,7 @@ f_count(argvars, rettv)
 	    }
 
 	    for ( ; li != NULL; li = li->li_next)
-		if (tv_equal(&li->li_tv, &argvars[1], ic))
+		if (tv_equal(&li->li_tv, &argvars[1], ic, FALSE))
 		    ++n;
 	}
     }
@@ -9418,7 +9435,7 @@ f_count(argvars, rettv)
 		if (!HASHITEM_EMPTY(hi))
 		{
 		    --todo;
-		    if (tv_equal(&HI2DI(hi)->di_tv, &argvars[1], ic))
+		    if (tv_equal(&HI2DI(hi)->di_tv, &argvars[1], ic, FALSE))
 			++n;
 		}
 	    }
@@ -12574,7 +12591,7 @@ f_index(argvars, rettv)
 	}
 
 	for ( ; item != NULL; item = item->li_next, ++idx)
-	    if (tv_equal(&item->li_tv, &argvars[1], ic))
+	    if (tv_equal(&item->li_tv, &argvars[1], ic, FALSE))
 	    {
 		rettv->vval.v_number = idx;
 		break;

src/testdir/test55.in

@@ -342,7 +342,18 @@ let l = [0, 1, 2, 3]
 :$put =(d == d)
 :$put =(l != deepcopy(l))
 :$put =(d != deepcopy(d))
+:"
+:" compare complex recursively linked list and dict
+:let l = []
+:call add(l, l)
+:let dict4 = {"l": l}
+:call add(dict4.l, dict4)
+:let lcopy = deepcopy(l)
+:let dict4copy = deepcopy(dict4)
+:$put =(l == lcopy)
+:$put =(dict4 == dict4copy)
 :endfun
+:"
 :call Test(1, 2, [3, 4], {5: 6})  " This may take a while
 :"
 :delfunc Test

src/testdir/test55.ok

@@ -109,3 +109,5 @@ caught a:000[3]
 1
 0
 0
+1
+1

src/version.c

@@ -714,6 +714,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    55,
 /**/
     54,
 /**/