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Date: Mon, 26 Oct 2015 20:39:55 +0800
Message-ID: <CABBJUpeZhyjjZ2nJwTdMjSCdq+Y1EBbm-9vLjsqEtN_qHNXpFQ@mail.gmail.com>
To: Dmitry Stogov <dmitry@zend.com>
Cc: Derick Rethans <derick@php.net>, Bob Weinand <bobwei9@hotmail.com>, 
	PHP Developers Mailing List <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Issues with exceptions and overloading opcodes
From: laruence@php.net (Xinchen Hui)

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Hey:

On Mon, Oct 26, 2015 at 8:11 PM, Dmitry Stogov <dmitry@zend.com> wrote:

> Hi,
>
> I'm going to re-fix the problem with the following patch:
>
> https://gist.github.com/dstogov/1eb77a9f2ff7dd807dd1
>
thanks, sorry I was busy last week, plan to do it tonight, but seems you
already fixed it. :)

thanks

>
>
> Thanks. Dmitry.
>
> On Thu, Oct 22, 2015 at 5:43 AM, Xinchen Hui <laruence@php.net> wrote:
>
>> Hey:
>>
>>
>>
>> On Wed, Oct 21, 2015 at 10:38 PM, Derick Rethans <derick@php.net> wrote:
>>
>>> On Tue, 20 Oct 2015, Bob Weinand wrote:
>>>
>>> > > Am 20.10.2015 um 18:08 schrieb Derick Rethans <derick@php.net>:
>>> > >
>>> > > On Tue, 20 Oct 2015, Bob Weinand wrote:
>>> > >
>>> > >>> Am 20.10.2015 um 17:11 schrieb Xinchen Hui <laruence@php.net>:
>>> > >>>
>>> > >>> On Tue, Oct 20, 2015 at 10:45 PM, Derick Rethans <derick@php.net
>>> <mailto:derick@php.net>> wrote:
>>> > >>>
>>> > >>>> When hacking on Xdebug for PHP 7, I ran into some issues where
>>> > >>>> PHP would just spin around. This happens when there is an
>>> > >>>> exception, and I use overloaded opcodes. I wrote a small example
>>> > >>>> extension at
>>> > >>>> https://github.com/derickr/php-minimal-opcode-overloading-exampl=
e
>>> > >>>> with a test case (
>>> > >>>>
>>> https://github.com/derickr/php-minimal-opcode-overloading-example/blob/=
master/tests/test.php
>>> > >>>> ) that shows that something is looping in executing opcodes, as
>>> > >>>> the HANDLE_EXCEPTION iirc doesn't advance to the next opline. I
>>> > >>>> believe this is a recent enough change, as it only started
>>> > >>>> happening after I upgraded from about RC1 to latest master.
>>> > >>>>
>>> > >>>> Would you care to have a look?
>>> > >>>>
>>> > >>> This is introduced by a fix made by Bob,
>>> > >>> https://github.com/php/php-src/commit/808f62bb
>>> > >>> <https://github.com/php/php-src/commit/808f62bb>
>>> > >>>
>>> > >>> Bob, I am going to revert this for now, since you didn't include =
a
>>> > >>> test script to show where the problem was, I am not sure why you
>>> > >>> made this?
>>> > >>
>>> > >> I didn't add any test case as we don't have any APIs in php-src
>>> > >> using that user_opcode handler. I discussed the change back then
>>> > >> with Dmitry and committed with his review.
>>> > >>
>>> > >> It concretely broke uopz which might throw an exception itself. An=
d
>>> > >> in turn we realized that for integrity we need to ensure that
>>> > >> opline =3D=3D EX(opline) else we'll end up with different behavior=
 in
>>> > >> global register builds and normal builds.
>>> > >>
>>> > >> In general, you should not overload ZEND_HANDLE_EXCEPTION (if you
>>> > >> need to, have a special handling for it, but never directly
>>> > >> dispatch to it). It is quite special being the only opcode actuall=
y
>>> > >> allowing EG(exception) to be non-NULL at the start of it.
>>> > >>
>>> > >> You are doing an #ifdef ZTS to exempt it=E2=80=A6 why don't you al=
ways
>>> > >> exempt it?
>>> > >
>>> > > Even if I do (like I've just pushed into the extension), the test
>>> > > still fails because the code loops. So you did break something.
>>> >
>>> > Ah, ZEND_CATCH indeed also allows EG(exception) to be non-null=E2=80=
=A6
>>> >
>>> > =E2=80=A6 maybe I should write
>>> >
>>> > if (EG(exception)
>>> >  && opline->opcode !=3D ZEND_HANDLE_EXCEPTION && opline->opcode !=3D
>>> ZEND_CATCH
>>> >  && ret !=3D ZEND_USER_OPCODE_DISPATCH && ret !=3D ZEND_USER_OPCODE_R=
ETURN
>>> && ret !=3D ZEND_USER_OPCODE_ENTER && ret !=3D ZEND_USER_OPCODE_LEAVE) =
{
>>> >     HANDLE_EXCEPTION();
>>> > }
>>> >
>>> > to allow dispatching for these two opcodes too?
>>>
>>> I don't know. Dmitry, Xinchen? I'd like to get this resolved soon..
>>>
>>> The commit which cause this problem has been reverted,  so this is
>> resolved , and regarding the problem which is commit tried to fixed, we
>> will find a better way to re-fix that.
>>
>> thanks
>>
>>> cheers,
>>> Derick
>>
>>
>>
>>
>> --
>> Xinchen Hui
>> @Laruence
>> http://www.laruence.com/
>>
>
>


--=20
Xinchen Hui
@Laruence
http://www.laruence.com/

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