Bug #76874 [Ver]: Documentation of memory leak in Xml Parser
Edit report at https://bugs.php.net/bug.php?id=76874&edit=1
ID: 76874
Updated by: cmb@php.net
Reported by: ksours at internetbrands dot com
Summary: Documentation of memory leak in Xml Parser
Status: Verified
Type: Bug
Package: Documentation problem
Operating System: Windows
PHP Version: 7.3.0beta3
Assigned To: cmb
Block user comment: N
Private report: N
New Comment:
Good catch, @ksours! This is not exactly the other bug, but it
seems it has the same root cause. If an object references a
resource, and this resource references that object, there is a
cycle that could only be resolved by the cyclic GC, but since
resources are not tracked (and that's unlikely to happen in the
future), it won't. The proper solution would be to turn the
parser resource into an object.
Previous Comments:
------------------------------------------------------------------------
[2018-09-12 20:42:51] ksours at internetbrands dot com
Poked this a little farther and determined there is some more nuance than I originally understood.
Here is the code to reproduce my case (can't seem to update the script field via the edit
interface)
<?php
class c
{
private $xml;
private $test;
public function test()
{
$this->xml = xml_parser_create();
xml_set_character_data_handler($this->xml, array(&$this, 'handle_cdata'));
xml_parser_free($this->xml);
$this->test = str_repeat('xxxxx', 1000000);
}
public function test2()
{
$xml = xml_parser_create();
xml_set_character_data_handler($xml, array(&$this, 'handle_cdata'));
xml_parser_free($xml);
$this->test = str_repeat('xxxxx', 1000000);
}
public function test3()
{
$this->xml = xml_parser_create();
xml_set_character_data_handler($this->xml, array(&$this, 'handle_cdata'));
xml_set_character_data_handler($this->xml, null);
xml_parser_free($this->xml);
$this->test = str_repeat('xxxxx', 1000000);
}
public function handle_cdata(&$parser, $data)
{
}
}
for($i = 1; $i < 100; $i++)
{
$object = new c();
$object->test();
unset($object);
var_dump(memory_get_usage(true) / (1024*1024));
}
?>
Note that test will show the memory leak, but test2 and test3 don't. I don't know if
that's the same as bug #72793 or not.
------------------------------------------------------------------------
[2018-09-12 17:26:05] cmb@php.net
> [â¦] but I assume there is some reason why this is not feasible
See bug #72793.
------------------------------------------------------------------------
[2018-09-12 16:01:37] ksours at internetbrands dot com
Description:
------------
There is a note on the xml_set_object that you need to unset the xml resource variable to avoid
memory leaks. This *really* needs to be more prominent. It's possible to hit this condition
in code that does not call xml_set_object and that's not the obvious place to look for
information on why xml_parser_free isn't working correctly.
Recommend at a minimum that a similar not be placed on the xml_parser_free entry. (Ideally calling
xml_parser_free *should* be sufficient to avoid holding that memory in place but I assume there is
some reason why this is not feasible).
------------------------------------------------------------------------
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