FAQ
Hi:

I would like to ask for a review of the solution for the following issue.
A patch is currently available at:
https://bugs.php.net/patch-display.php?bug=55214&patch=__CLASS__-in-traits.002.patch&revision=1311532096

The problem is that __CLASS__ used in the body of a trait method does
not behave as expected based on the advertised metaphor that traits
are some kind of compiler-assisted copy'n'past.

This patch provides this semantic, thus, __CLASS__ will correspond to
the class name of the class where the trait is actually used.

However, my solution is very hackish: I changed the implementation of
how __CLASS__ is handled, and instead of setting the class name on the
zval, I set the zval to IS_NULL, and one of the unused data members as
a flag identifying this NULL value to be special.

This flag is later checked when the methods are actually copied into
the class, and the zval is replaced by the actual expected class name.
To be able to garbage collect the created zval later, it is included
in the list of literals of the method.

However, I do not have any clue on what kind of invariants are
associated to literals, nor what there actual semantics is supposed to
be.
This is mainly because of our implicit policy of keeping the engine
code free from any comments.

Thus, I would really like a comment on this patch, otherwise I will
commit it next week and also add the missing __TRAIT__ magic variable
to mirror the __CLASS__ behavior in a trait.

Thanks a lot
Stefan

PS: just noted there might be at least one more bug. note to self: add
a test for a traits that is used by a trait that is used by a class


-------- Original Message --------
Edit report at https://bugs.php.net/bug.php?id=55214&edit=1

ID:                 55214
Comment by:         gron@php.net
Reported by:        chris dot rutledge at gmail dot com
Summary:            use of __CLASS__ within trait returns trait name not
class name
Status:             Assigned
Type:               Bug
Package:            Scripting Engine problem
Operating System:   Ubuntu
PHP Version:        5.4.0alpha1
Assigned To:        gron
Block user comment: N
Private report:     N

New Comment:

Ok, updated the patch and would like to ask for a review.
This is still hacky, but now I use the literals of a function to be
able to clean up the zval for the __CLASS__ name. Thus, the memory
leak should be fixed.

Think we will still need a __TRAIT__ to mirror __CLASS__ and to get
the trait name itself when that is required.

The test case is missing in the patch:

--TEST--
Bug #55214 (Use of __CLASS__ within trait returns trait name not class name)
--FILE--
<?php

trait ATrait {
public static function get_class_name() {
return __CLASS__;
}

public function get_class_name_obj() {
return __CLASS__;
}
}


class SomeClass {
use ATrait;
}

$r = SomeClass::get_class_name();
var_dump($r);

$o = new SomeClass();
$r = $o->get_class_name_obj();
var_dump($r);

?>
--EXPECT--
string(9) "SomeClass"
string(9) "SomeClass"


Previous Comments:
------------------------------------------------------------------------
[2011-07-24 18:28:16] gron@php.net

The following patch has been added/updated:

Patch Name: __CLASS__-in-traits.002.patch
Revision:   1311532096
URL:        https://bugs.php.net/patch-display.php?bug=55214&patch=__CLASS__-in-traits.002.patch&revision=1311532096

------------------------------------------------------------------------
[2011-07-23 17:53:25] gron@php.net

I attached a patch of how a fix could be done.

I have to admit that it is hacky, but I think this is the expected
behavior with respect to the metaphor of compiler assisted
copy'n'past.

However, the patch is problematic, since it introduces a new memory leak.
And I do not have a good strategy yet to fix it.

Not sure how another patch could work, but the general idea is that
__CLASS__ is not actually defined inside a trait (BTW: we should add
__TRAIT__, too, yes).
Thus, it resolves to a IS_NULL value.
And as it happens to be, IS_NULL makes all is data members invalid,
and I use that to indicate that it isn't actually a NULL value but
that I want to fix it up with the class name when the method is
actually flattened/copied into the class.

The problem with the memory leak comes from the fact that copying the
method is not actually done deeply but shallow. And, I do not know how
to free only my fixed up names/ZVALs :-/.

------------------------------------------------------------------------
[2011-07-23 17:45:28] gron@php.net

The following patch has been added/updated:

Patch Name: __CLASS__-in-traits.patch
Revision:   1311443128
URL:        https://bugs.php.net/patch-display.php?bug=55214&patch=__CLASS__-in-traits.patch&revision=1311443128

------------------------------------------------------------------------
[2011-07-23 14:17:24] felipe@php.net

It's simple to add the __TRAIT__ one, just like __CLASS__ does.

But making a more magic __CLASS__ to reflect the class that called is
too much magic, hacky. Whereas we are currently doing the __CLASS__
substitution on compile-time.

------------------------------------------------------------------------
[2011-07-22 04:56:04] gron@php.net

Felipe: I tend to disagree, too.

I do not think this is expected behavior.
Will have a look at this, and another bug reported on the QA mailing
list hopefully at the weekend.

Best regards
Stefan

------------------------------------------------------------------------


The remainder of the comments for this report are too long. To view
the rest of the comments, please view the bug report online at

https://bugs.php.net/bug.php?id=55214


--
Edit this bug report at https://bugs.php.net/bug.php?id=55214&edit=1

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