Bug #64741 [Nab]: Various ways to reassign this
Edit report at https://bugs.php.net/bug.php?id=64741&edit=1
ID: 64741
User updated by: php dot bugs at daverandom dot com
Reported by: php dot bugs at daverandom dot com
Summary:Various ways to reassign this
Status: Not a bug
Type: Bug
Package:Scripting Engine problem
Operating System: Any
PHP Version:Irrelevant
Block user comment: N
Private report: N
New Comment:
I accept that the bulk of the examples below are difficult/impossible to
prevent
with the static analysis that happens at compile time, given the range of
dynamic ways to do this that makes PHP a great language. I too would not like
to
see PEBKAC prevention affecting performance.
However, I think there is one example above that warrants further inspection:
unset($this) actually causes a segfault (this can be seen here:
http://codepad.viper-7.com/NX7v1q) and should be detectable at compile time
fairly easily/inexpensively I would have thought, although I'm no expert on the
PHP src.
Previous Comments:
[2013-04-30 11:52:38] johan...@php.net
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php
we prevent from mistakes, we don't prevent people from shooting in their feed,
especially as such checks would slow down *all* variable access.
[2013-04-30 11:42:15] php dot bugs at daverandom dot com
Description:
The engine prevents userland code from directly reassigning $this with a
compile
time error, but it does not prevent a number of other mechanisms. The following
are all possible:
unset($this);
// ...
public function test()
{
${'th'.'is'} = 'foo';
}
// ...
public function test()
{
$foo = 'this';
$$foo = 'foo';
}
// ...
function ref(&$arg)
{
$arg = 'foo';
}
public function test()
{
ref($this);
}
Test script:
---
test1();
(new ThisReassignments)->test2();
(new ThisReassignments)->test3();
// NB: unset() causes a segmentation fault and doesn't *really* work, but
it should emit a meaningful error
Expected result:
Fatal error with a meaningful error message in all cases
Actual result:
--
object(ThisReassignments)#1 (0) {
}
string(3) "foo"
object(ThisReassignments)#1 (0) {
}
string(3) "foo"
object(ThisReassignments)#1 (0) {
}
string(3) "foo"
--
Edit this bug report at https://bugs.php.net/bug.php?id=64741&edit=1
[PHP-BUG] Bug #64741 [NEW]: Various ways to reassign this
From: php dot bugs at daverandom dot com
Operating system: Any
PHP version: Irrelevant
Package: Scripting Engine problem
Bug Type: Bug
Bug description:Various ways to reassign this
Description:
The engine prevents userland code from directly reassigning $this with a
compile
time error, but it does not prevent a number of other mechanisms. The
following
are all possible:
unset($this);
// ...
public function test()
{
${'th'.'is'} = 'foo';
}
// ...
public function test()
{
$foo = 'this';
$$foo = 'foo';
}
// ...
function ref(&$arg)
{
$arg = 'foo';
}
public function test()
{
ref($this);
}
Test script:
---
test1();
(new ThisReassignments)->test2();
(new ThisReassignments)->test3();
// NB: unset() causes a segmentation fault and doesn't *really* work,
but it should emit a meaningful error
Expected result:
Fatal error with a meaningful error message in all cases
Actual result:
--
object(ThisReassignments)#1 (0) {
}
string(3) "foo"
object(ThisReassignments)#1 (0) {
}
string(3) "foo"
object(ThisReassignments)#1 (0) {
}
string(3) "foo"
--
Edit bug report at https://bugs.php.net/bug.php?id=64741&edit=1
--
Try a snapshot (PHP 5.4):
https://bugs.php.net/fix.php?id=64741&r=trysnapshot54
Try a snapshot (PHP 5.3):
https://bugs.php.net/fix.php?id=64741&r=trysnapshot53
Try a snapshot (trunk):
https://bugs.php.net/fix.php?id=64741&r=trysnapshottrunk
Fixed in SVN: https://bugs.php.net/fix.php?id=64741&r=fixed
Fixed in release: https://bugs.php.net/fix.php?id=64741&r=alreadyfixed
Need backtrace: https://bugs.php.net/fix.php?id=64741&r=needtrace
Need Reproduce Script: https://bugs.php.net/fix.php?id=64741&r=needscript
Try newer version: https://bugs.php.net/fix.php?id=64741&r=oldversion
Not developer issue:https://bugs.php.net/fix.php?id=64741&r=support
Expected behavior: https://bugs.php.net/fix.php?id=64741&r=notwrong
Not enough info:
https://bugs.php.net/fix.php?id=64741&r=notenoughinfo
Submitted twice:
https://bugs.php.net/fix.php?id=64741&r=submittedtwice
register_globals: https://bugs.php.net/fix.php?id=64741&r=globals
PHP 4 support discontinued: https://bugs.php.net/fix.php?id=64741&r=php4
Daylight Savings: https://bugs.php.net/fix.php?id=64741&r=dst
IIS Stability: https://bugs.php.net/fix.php?id=64741&r=isapi
Install GNU Sed:https://bugs.php.net/fix.php?id=64741&r=gnused
Floating point limitations: https://bugs.php.net/fix.php?id=64741&r=float
No Zend Extensions: https://bugs.php.net/fix.php?id=64741&r=nozend
MySQL Configuration Error: https://bugs.php.net/fix.php?id=64741&r=mysqlcfg
