Edit report at https://bugs.php.net/bug.php?id=62452&edit=1
ID: 62452
Comment by: ni...@php.net
Reported by: hanskrentel at yahoo dot de
Summary: Variable Aliasing does not work in Closure
Status: Re-Opened
Type: Bug
Package: Scripting Engine problem
Operating System: Multiple
PHP Version: Irrelevant
Block user comment: N
Private report: N
New Comment:
I just looked into this a bit but couldn't find a good way to fix it. The main
issue is that the prototype hack is only done in ZEND_INIT_FCALL_BY_NAME and
only for VARs. Doing the same for CVs (as in this case) would be easy, but it
sadly does not work properly if the closure is also invoked using
call_user_func or any other function using zend_call_function internally.
zend_call_function does not back the closure into the prototype and due to the
way it works I'm not sure how this could be added there. For zcf the
get_closure object handler call is done within zend_is_callable_ex and the
results are put into the passed function_call_cache then. But the fcc can be
reused for multiple calls (or not be used at all), so I really don't know how
to do this safely without causing leaks or double frees.
Previous Comments:
------------------------------------------------------------------------
[2012-07-03 17:49:27] ni...@php.net
@laruence: The closure can still exist even if it is not referenced by $f
anymore. I didn't look into this yet, but the fix should be along the lines of
adding a ref to the closure when it is called and removing it again when it
finishes running. Actually, I remember seeing something in the code that backs
up the function zval into op_array.prototype (disguised as a zend_function*)
and dtors it in the leave_helper. But clearly that isn't enough yet.
------------------------------------------------------------------------
[2012-07-03 17:39:24] hanskrentel at yahoo dot de
hi @laurence, thank's for taking the time to review it. If I write code like
unset($this);
it does not fatal error either (you can not destroy a object while you are
calling
it.).
Also I don't want to destroy the closure, I just want to re-use that variable.
Can't you just let the garbage collector do the dirty work?
------------------------------------------------------------------------
[2012-07-02 07:03:19] larue...@php.net
you can not destroy a closure while you are calling it.
when you override $f in $f, zend vm try to destroy the closure $f, since the
refcout of it is 1.
try following :
$b = $f = function() use (&$f) {
$f = function() {};
};
$f();
$f();
------------------------------------------------------------------------
[2012-06-29 20:05:06] ni...@php.net
Verified on master.
------------------------------------------------------------------------
[2012-06-29 19:53:22] hanskrentel at yahoo dot de
Description:
------------
It's not possible to make use of variable aliasing in PHP when the alias is
used
within the use clause of a lambda function construct that is assigned to that
variable (recursion).
PHP denies to do what it is commanded with a Fatal error: Cannot destroy active
lambda function. But the function is not destroyed. It's just not that the
variable container contains the identifier of it.
I'd like to change that, and I don't want to waste another variable name. Also
I
don't understand how I can actually destroy something I should not have any
access
to from PHP userland.
Or if that is intended, please allow us to destroy the active lambda making the
function return NULL and continue to execute.
Test script:
---------------
$f = function() use (&$f) {
$f = function() {echo "hello"};
};
$f();
$f();
Expected result:
----------------
hello
Actual result:
--------------
Fatal error: Cannot destroy active lambda function
------------------------------------------------------------------------
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Edit this bug report at https://bugs.php.net/bug.php?id=62452&edit=1
