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Date: Thu, 22 Oct 2015 10:43:55 +0800
Message-ID: <CABBJUpdyraZS_VEsF-tRdEF4cMsoQw=BRCWuFc-YqFJzGFD57g@mail.gmail.com>
To: Derick Rethans <derick@php.net>
Cc: Bob Weinand <bobwei9@hotmail.com>, Dmitry Stogov <dmitry@zend.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 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-example
> > >>>> with a test case (
> > >>>>
> https://github.com/derickr/php-minimal-opcode-overloading-example/blob/ma=
ster/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. And
> > >> 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 i=
n
> > >> 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 actually
> > >> 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 alwa=
ys
> > >> 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_RET=
URN
> && 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




--=20
Xinchen Hui
@Laruence
http://www.laruence.com/

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