#36847 [Opn]: debug_backtrace() result is not unset and eats memory
| From: | dmitry@php.net | Date: | Thu, 13 Apr 2006 06:03:27 +0000 |
| Subject: | #36847 [Opn]: debug_backtrace() result is not unset and eats memory | ||
| References: | 1 | Groups: | php.doc |
| Request: | Send a blank email to phpdoc+get-969372672@lists.php.net to get a copy of this message | ||
ID: 36847
Updated by: dmitry@php.net
Reported By: toggg@php.net
Status: Open
Bug Type: Documentation problem
Operating System: fc3
PHP Version: 5CVS-2006-03-24 (snap)
Assigned To: dmitry
New Comment:
__destruct() is not called because object is not destroyed (it is still
referenced from inside). unset() just destroy reference to object from
variable $ret;
We need add information about 'object' field into debug_backtrace()
documentation.
Previous Comments:
------------------------------------------------------------------------
[2006-04-12 12:48:21] toggg@php.net
OK, nice, that explains the difference to php4.
unset($res) is not sufficient ... obviously,
<?php
class test
{
var $backtrace = null;
function test()
{
$this->backtrace = debug_backtrace();
unset($this->backtrace[0]['object']);
}
}
set_time_limit(0);
for($i = 0; $i <= 500000; $i++) {
$ret = &new test();
unset($ret);
}
?>
does not break anymore.
However, this circular reference is due to the new 'object' returned by
debug_backtrace() which is not documented.
It merits a *big* warning.
Also, it had been nice to be able to do it by __destruct() , but it's
not called by unset() ...
I report back to pear , thanks !
------------------------------------------------------------------------
[2006-04-12 11:58:42] dmitry@php.net
Backtrace information that is returned from debug_backtrace() contains
reference to $this object. So this examle creates circular data
structure.
PHP cannot free circular structures at runtime and does free them on
request shutdown.
So this bug is the same as bug #33595 (recursive references leak
memory).
------------------------------------------------------------------------
[2006-03-26 06:09:54] toggg@php.net
This not the same situation as #33487
Here, it's not a question of local variable within a method.
And we actually unset the created object.
If I do the same with $this->backtrace = str_pad(' ', 2300); then the
memory is not eaten up.
This occurs only if debug_backtrace() result is affected to a property
of the test object.
------------------------------------------------------------------------
[2006-03-26 01:03:57] tony2001@php.net
Duplicate of bug #33487.
------------------------------------------------------------------------
[2006-03-24 16:56:03] toggg@php.net
Description:
------------
It was originated by http://pear.php.net/bugs/bug.php?id=6788
Reproduce code:
---------------
<?php
class test
{
var $backtrace = null;
function test()
{
$this->backtrace = debug_backtrace();
}
}
set_time_limit(0);
for($i = 0; $i <= 10000; $i++) {
$ret = &new test();
unset($ret);
}
?>
Expected result:
----------------
nothing
Actual result:
--------------
memory exhausted
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=36847&edit=1