#45145 [Opn->Csd]: reference aliasing is working backwards, wiping the var

From: Date: Mon, 02 Jun 2008 08:56:23 +0000
Subject: #45145 [Opn->Csd]: reference aliasing is working backwards, wiping the var
References: 1  Groups: php.bugs 
Request: Send a blank email to php-bugs+get-125421@lists.php.net to get a copy of this message 
 ID:               45145
 User updated by:  phpbug at thoria dot org
 Reported By:      phpbug at thoria dot org
-Status:           Open
+Status:           Closed
 Bug Type:         Variables related
 Operating System: Linux
 PHP Version:      5.2CVS-2008-06-01 (snap)
 New Comment:

Arrrhhh. I'm just guilty of C-thinking.


Previous Comments:
------------------------------------------------------------------------

[2008-06-02 08:34:19] phpbug at thoria dot org

Now, I'm really scratching my head. After hacking my code down for
hours, I realised it could be replicated in a few lines. Iteration 1 is
OK. Iteration 2 produces the effect. The unset is not necessary.
Iteration 3 shows how it goes away if $x='moo' is declared first.

<?php

echo "1<br>";

$y = "original string";
$x = "moo";
unset($x);
$x = &$y;
echo "X $x  Y $y<br><br>";

echo "2<br>";

$y = "original string";
$x = "moo";
unset($x);
$x = &$y;
echo "X $x  Y $y<br><br>";

echo "3<br>";

$x = "moo";
$y = "original string";
$x = &$y;
echo "X $x  Y $y<br><br>";

?>

------------------------------------------------------------------------

[2008-06-01 14:35:37] phpbug at thoria dot org

Description:
------------
On versions 5.2.3 and 4.3.1(Zend off), on different shared hosting
servers.

Within one large function/loop in my app

$x = &$y;

y is destroyed and replaced by x, intermittently. unset($x) is ignored
if placed above it, and x still goes into y. There is no workaround,
besides using $x = $y. I think any ref assignments in this loop behave
like this if $x has had a prior value.

You will need to have my whole app installed. It's so weird, it makes
me feel dumb to submit it.

Reproduce code:
---------------
$bb = "original string";
$aa = "moo";
unset($aa);
$aa = &$bb;
echo "AA->$aa, BB->$bb <br>";

or

$bb = "original string";
$aa = "moo";
$aa = &$bb;
echo "AA->$aa, BB->$bb <br>";

The following is OK

$aa = "moo";
$bb = "original string";
$aa = &$bb;
echo "AA->$aa, BB->$bb <br>";

Expected result:
----------------
AA->original string, BB->original string 
AA->original string, BB->original string 
AA->original string, BB->original string 

Actual result:
--------------
AA->original string, BB->original string 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->original string, BB->original string 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->original string, BB->original string 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->moo, BB->moo 
AA->original string, BB->original string 
AA->moo, BB->


------------------------------------------------------------------------


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