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[2008-06-04 16:57 UTC] thomas dot jarosch at intra2net dot com
Description: ------------ Hello together, I'm currently trying to find a heap corruption while using Horde and noticed a rather odd behavior. The supplied code is the standard way Horde does it singletons. We always used the syntax of "$object = &new class" to make it work with PHP4 and PHP5. If I change that to "$object = new class", everything works as expected. I've found bug #32845 and noticed what we are doing seems wrong, so Horde needs fixing. The problem gets worse if the class object contains a variable of the type "PEAR_Error", which contains cyclic references. Not only does the constructor get called every time, the object leaks memory like hell, even with PHP 5.3. I've searched through the bugtracker and thought the garbage collector now handles cyclic references, but maybe this is a side-effect of something else going wrong. Is the memory consumption by design? Thanks in advance for any comment, Thomas Reproduce code: --------------- <?php require_once "PEAR.php"; class Horde_History { var $error; function &singleton() { static $history; if (!isset($history)) { $history = &new Horde_History(); } return $history; } function Horde_History() { $this->error = PEAR::raiseError("error"); echo "Memory usage: " . memory_get_usage() . "\n"; } } for (;;) { $a = Horde_History::singleton(); } Expected result: ---------------- Constant memory usage. Actual result: -------------- Increasing memory usage. PatchesPull RequestsHistoryAllCommentsChangesGit/SVN commits
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At first, you have a serious issue in your code. "static" variables MUST NOT be asigned by reference, because they are already references. As result the singleton pattern just doesn't work. BTW the bug is really exists. The simplified test case follows(changing "=& new" into "= new" fixes memory corruption). <?php class Horde_History { function raiseError() { return debug_backtrace(); } function Horde_History() { $this->error = $this->raiseError(); echo "Memory usage: " . memory_get_usage() . "\n"; } } for ($i=0;$i<100000;$i++) { $a =& new Horde_History(); } ?>The simplest case for this memory corruption. <?php class Foo { function Foo() { $this->error = array($this,$this); } } $a =& new Foo();