Bug #79726 [Opn]: SplStack::pop breaks stack validity
Edit report at https://bugs.php.net/bug.php?id=79726&edit=1
ID: 79726
Updated by: cmb@php.net
Reported by: millet dot gael at gmail dot com
Summary: SplStack::pop breaks stack validity
Status: Open
Type: Bug
Package: SPL related
Operating System: OSX
PHP Version: 7.4.7
Block user comment: N
Private report: N
New Comment:
The behavior likely changed due to fixing bug #79151. In my
opinion, this change is not a bug, but rather the given test code
is invalid; valid alternatives would be <https://3v4l.org/fZKT8>
and <https://3v4l.org/HLrZn>.
Previous Comments:
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[2020-06-24 07:03:33] millet dot gael at gmail dot com
I fixed my code, but I think it's still a bug.
Here is the weirdest part : https://3v4l.org/GPvYk
The previous code is working with 7.2.0 - 7.3.14, 7.4.0 - 7.4.2 and fails with 7.3.15 - 7.3.19,
7.4.3 - 7.4.7
The behaviour is unpredictable depending of the php version.
------------------------------------------------------------------------
[2020-06-23 14:45:17] Wes dot example at example dot org
The fact that worked before was probably accidental. Changing any data structure while iterating
over it, will produce this sort of errors. That's not just SPL or PHP, but happens in any
programming language, and it's disallowed by design in most of the times.
Your specific bug can be fixed, probably, but you should avoid that sort of code anyway. If you get
any kind of reasonable result from doing this, always consider it a hack, or accidental. Unless you
are actually iterating over a copy (like PHP arrays) or using something like ->filter()
array_filter() functions.
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[2020-06-23 14:25:49] millet dot gael at gmail dot com
Description:
------------
Breaking change on SplStack iterator.
If we pop from the stack, the stack become invalid for the last iteration.
This code was working with php 7.2.x, but is broken with 7.3.x and 7.4.x
Can be fixed by adding "$stack->rewind();" after "$stack->next();"
Test script:
---------------
<?php
$stack = new \SplStack();
$stack->push(1);
$stack->push(2);
$stack->rewind();
while ($stack->valid()) {
$value = $stack->pop();
var_dump($value);
$stack->next();
}
Expected result:
----------------
int(2)
int(1)
Actual result:
--------------
int(2)
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=79726&edit=1
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