Bug #72598 [Ana]: Reference is lost after array_slice()
Edit report at https://bugs.php.net/bug.php?id=72598&edit=1
ID: 72598
Updated by: dmitry@php.net
Reported by: dominikschilling+php at gmail dot com
Summary: Reference is lost after array_slice()
Status: Analyzed
Type: Bug
Package: Scripting Engine problem
PHP Version: 7.1Git-2016-07-14 (Git)
Block user comment: N
Private report: N
New Comment:
There are two fixes proposed:
https://github.com/php/php-src/pull/2059
https://github.com/php/php-src/pull/2085
Previous Comments:
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[2016-08-09 12:20:39] dominikschilling+php at gmail dot com
I'm curious what the status of this bug is.
I've added the scripts to 3v4l.org to compare the output of different PHP versions:
Script from comment 1: https://3v4l.org/MCmnj, warning exists
in 7.1.0alpha2 - 7.1.0beta1
Script from comment 2: https://3v4l.org/WECs1, 7.0.0 -
7.1.0beta1 produces only one warning, 5.3.0 - 5.6.24 has two
Another (unrelated?) script: https://3v4l.org/fESuN#v530,
I noticed this because I got the (valid) warning after upgrading to 7.0.9.
------------------------------------------------------------------------
[2016-07-15 20:06:22] nikic@php.net
@dmitry: This warning/behavior has been around since forever, I don't understand why we should
change it now. call_user_func_array() can't create a reference into the array, so we can only
do a by-reference pass if the element is already a reference. If there's no existing reference,
the call will not work correctly. (If the by-reference passing does not actually matter, then one
should not use by-reference passing...)
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[2016-07-15 08:47:28] dmitry@php.net
The problem is not related to $this handling at all.
Test script:
---------------
<?php
function ref(&$a) {
var_dump($a);
}
$b = 1;
$args = [&$b];
unset($b);
for ($i = 0; $i < 2; $i++) {
$a = array_slice($args, 0, 1);
call_user_func_array('ref', $a);
}
?>
Expected result:
----------------
int(1)
int(1)
Actual result:
--------------
int(1)
PHP Warning: Parameter 1 to ref() expected to be a reference, value given in %s on line %d
I think this warning doesn't make a lot of sense at all, or at least it shouldn't prevent
execution of the called function.
Fixing this is a new minor BC break.
------------------------------------------------------------------------
[2016-07-14 21:33:07] bwoebi@php.net
Yes, it should already fail at the first iteration I think.
Modification of $this means the content of the $this variable itself, not the object.
I.e. $this must never become another object or scalar.
@dmitry yeah, that's a workaround, but it's only a workaround for the bug⦠the bug
needs to be fixed somehow though before 7.1.0. I don't find this broken behavior acceptable to
be shipped in the release.
------------------------------------------------------------------------
[2016-07-14 20:45:45] dominikschilling+php at gmail dot com
Thanks for link to the RFC. I think I'm missing the point why "re-assign $this" ==
"modification of $this" which is basically "$this = 'something'" vs.
"$this->something = 'something'".
For example the following script is still working and also a modification of $this, although
it's another context:
class C {
public $b;
function foo(){
$this->b = 'a';
}
}
$x = new C;
$x->foo();
var_dump($x->b); // Prints a
> That it needs two iterations is another bug in array_slice
Does that now mean that it should already fail on the first iteration?
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