From: Yusuke Endoh <redmine@...>
Date: 2010-03-02T01:27:49+09:00
Subject: [ruby-core:28386] [Bug #2184] Blocks strange behavior

Issue #2184 has been updated by Yusuke Endoh.


Hi,

> 1.9.1:
> z = lambda {|x,y| x <=> y}
> [3,2,1].max(&z) # => ArgumentError: wrong number of arguments (1 for 2)
>
> But it works in 1.9:
> z = lambda {|x| x[0] <=> x[1]}
> [3,2,1].max(&z) # => 3


Since r11431, 1.9 had been optimized Enumerable#each_with_index, min
and max by reusing array for yield parameters.  This causes the above
behavior.

But the optimization was found wrong in [ruby-dev:32181], which may
cause unexpected behaviors:

  $ ./ruby -e '(1..5).max {|a| p a; a << :foo; a[0] <=> a[1] }'
  [2, 1]
  [3, 2, :foo]
  [4, 3, :foo, :foo]
  [5, 4, :foo, :foo, :foo]  <= unexpected accumulation

  $ ./ruby -e 'b = nil; (1..5).max {|a| p a; b ||= a.freeze; a[0] <=> a[1] }; p b'
  [2, 1]
  [3, 2]
  [4, 3]
  [5, 4]
  [5, 4]  <= expected [2, 1]

So, the opt of Enumerable#each_with_index was reverted, but min and
max seemed to be forgotten.

Here is a patch to fix Enumerable#min, max and minmax.  Unless anyone
expresses opposition, I'll commit.


diff --git a/enum.c b/enum.c
index 6eeb62c..4f930ae 100644
--- a/enum.c
+++ b/enum.c
@@ -1058,10 +1058,7 @@ min_ii(VALUE i, VALUE *memo, int argc, VALUE *argv)
 	*memo = i;
     }
     else {
-	VALUE ary = memo[1];
-	RARRAY_PTR(ary)[0] = i;
-	RARRAY_PTR(ary)[1] = *memo;
-	cmp = rb_yield(ary);
+	cmp = rb_yield_values(2, i, *memo);
 	if (rb_cmpint(cmp, i, *memo) < 0) {
 	    *memo = i;
 	}
@@ -1087,18 +1084,16 @@ min_ii(VALUE i, VALUE *memo, int argc, VALUE *argv)
 static VALUE
 enum_min(VALUE obj)
 {
-    VALUE result[2];
+    VALUE result = Qundef;
 
-    result[0] = Qundef;
     if (rb_block_given_p()) {
-	result[1] = rb_ary_new3(2, Qnil, Qnil);
-	rb_block_call(obj, id_each, 0, 0, min_ii, (VALUE)result);
+	rb_block_call(obj, id_each, 0, 0, min_ii, (VALUE)&result);
     }
     else {
-	rb_block_call(obj, id_each, 0, 0, min_i, (VALUE)result);
+	rb_block_call(obj, id_each, 0, 0, min_i, (VALUE)&result);
     }
-    if (result[0] == Qundef) return Qnil;
-    return result[0];
+    if (result == Qundef) return Qnil;
+    return result;
 }
 
 static VALUE
@@ -1131,10 +1126,7 @@ max_ii(VALUE i, VALUE *memo, int argc, VALUE *argv)
 	*memo = i;
     }
     else {
-	VALUE ary = memo[1];
-	RARRAY_PTR(ary)[0] = i;
-	RARRAY_PTR(ary)[1] = *memo;
-	cmp = rb_yield(ary);
+	cmp = rb_yield_values(2, i, *memo);
 	if (rb_cmpint(cmp, i, *memo) > 0) {
 	    *memo = i;
 	}
@@ -1159,24 +1151,21 @@ max_ii(VALUE i, VALUE *memo, int argc, VALUE *argv)
 static VALUE
 enum_max(VALUE obj)
 {
-    VALUE result[2];
+    VALUE result = Qundef;
 
-    result[0] = Qundef;
     if (rb_block_given_p()) {
-	result[1] = rb_ary_new3(2, Qnil, Qnil);
-	rb_block_call(obj, id_each, 0, 0, max_ii, (VALUE)result);
+	rb_block_call(obj, id_each, 0, 0, max_ii, (VALUE)&result);
     }
     else {
-	rb_block_call(obj, id_each, 0, 0, max_i, (VALUE)result);
+	rb_block_call(obj, id_each, 0, 0, max_i, (VALUE)&result);
     }
-    if (result[0] == Qundef) return Qnil;
-    return result[0];
+    if (result == Qundef) return Qnil;
+    return result;
 }
 
 struct minmax_t {
     VALUE min;
     VALUE max;
-    VALUE ary;
     VALUE last;
 };
 
@@ -1242,17 +1231,11 @@ minmax_ii_update(VALUE i, VALUE j, struct minmax_t *memo)
 	memo->max = j;
     }
     else {
-	VALUE ary = memo->ary;
-
-        rb_ary_store(ary, 0, i);
-        rb_ary_store(ary, 1, memo->min);
-	n = rb_cmpint(rb_yield(ary), i, memo->min);
+	n = rb_cmpint(rb_yield_values(2, i, memo->min), i, memo->min);
 	if (n < 0) {
 	    memo->min = i;
 	}
-        rb_ary_store(ary, 0, j);
-        rb_ary_store(ary, 1, memo->max);
-	n = rb_cmpint(rb_yield(ary), j, memo->max);
+	n = rb_cmpint(rb_yield_values(2, j, memo->max), j, memo->max);
 	if (n > 0) {
 	    memo->max = j;
 	}
@@ -1264,7 +1247,7 @@ minmax_ii(VALUE i, VALUE _memo, int argc, VALUE *argv)
 {
     struct minmax_t *memo = (struct minmax_t *)_memo;
     int n;
-    VALUE ary, j;
+    VALUE j;
 
     ENUM_WANT_SVALUE();
 
@@ -1275,10 +1258,7 @@ minmax_ii(VALUE i, VALUE _memo, int argc, VALUE *argv)
     j = memo->last;
     memo->last = Qundef;
 
-    ary = memo->ary;
-    rb_ary_store(ary, 0, j);
-    rb_ary_store(ary, 1, i);
-    n = rb_cmpint(rb_yield(ary), j, i);
+    n = rb_cmpint(rb_yield_values(2, j, i), j, i);
     if (n == 0)
         i = j;
     else if (n < 0) {
@@ -1317,7 +1297,6 @@ enum_minmax(VALUE obj)
     memo.min = Qundef;
     memo.last = Qundef;
     if (rb_block_given_p()) {
-	memo.ary = ary;
 	rb_block_call(obj, id_each, 0, 0, minmax_ii, (VALUE)&memo);
         if (memo.last != Qundef)
             minmax_ii_update(memo.last, memo.last, &memo);

-- 
Yusuke ENDOH <mame@tsg.ne.jp>
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http://redmine.ruby-lang.org/issues/show/2184

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