ID: 47103
Updated by: lbarn...@php.net
Reported By: soywiz at gmail dot com
-Status: Verified
+Status: Bogus
Bug Type: Scripting Engine problem
Operating System: *
PHP Version: 5.*CVS,6CVS (2009-01-15)
New Comment:
This is not a bug.
> $a = array_fill(0, 99999, str_repeat('*', 9991));
This adds 99999 times the *same* string to the array. This string ends
with a refcount of 99999, and the array occupies only the memory
required for *one* string of 9991 bytes.
> foreach ($a as &$v) ;
At this point the engine must duplicate the string, place it at the
current index, and return a reference to it (because if you assign to
it, you do not want all values of the array to be changed at once).
When you unset $v, you remove a reference from it, and leave a copy in
the array.
You get closely the same memory usage with the following script, which
does the same thing:
$a = array();
for($i = 0; $i < 99999; ++$i) {
$a[] = str_repeat('*', 9991);
}
foreach ($a as &$v);
Previous Comments:
------------------------------------------------------------------------
[2009-01-15 14:52:56] j...@php.net
This worked:
# php -dmemory_limit=1000M t.php
int(1018887988)
That number is from memory_get_usage() after the foreach.. :)
------------------------------------------------------------------------
[2009-01-15 14:51:25] j...@php.net
This is NOT expected but might not be fixable. And foreach with
reference is supposed to work without leaks.
------------------------------------------------------------------------
[2009-01-14 17:35:42] crrodriguez at opensuse dot org
looks like expected, do not use foreach value by reference, it is know
to have "apparently unexpected behaviors" that are normal.
------------------------------------------------------------------------
[2009-01-14 16:35:07] soywiz at gmail dot com
Description:
------------
This snippet causes an out of memory. It seems that it's duplicating
the value (it's trying to allocate a memory chunk as large as each
element on the array) and it's not freeing it.
The problem persists even with a unset($v); within the foreach.
I reproduced it using php 5.2.8-cli on windows and php 5.2.5-cgi on
linux.
I think it should work, but maybe it's a php feature?
Reproduce code:
---------------
<?php
$a = array_fill(0, 99999, str_repeat('*', 9991));
foreach ($a as &$v) ;
?>
Expected result:
----------------
Don't waste all the memory
Actual result:
--------------
Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to
allocate 9992 bytes) in test.php on line 3
------------------------------------------------------------------------
--
Edit this bug report at http://bugs.php.net/?id=47103&edit=1
