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Date: Tue, 20 Oct 2015 17:08:26 +0100 (BST)
To: Bob Weinand <bobwei9@hotmail.com>
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Subject: Re: [PHP-DEV] Issues with exceptions and overloading opcodes
From: derick@php.net (Derick Rethans)

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On Tue, 20 Oct 2015, Bob Weinand wrote:

> > Am 20.10.2015 um 17:11 schrieb Xinchen Hui <laruence@php.net>:
> >=20
> > On Tue, Oct 20, 2015 at 10:45 PM, Derick Rethans <derick@php.net <mailt=
o:derick@php.net>> wrote:
> >=20
> >> When hacking on Xdebug for PHP 7, I ran into some issues where PHP=20
> >> would just spin around. This happens when there is an exception,=20
> >> and I use overloaded opcodes. I wrote a small example extension at=20
> >> https://github.com/derickr/php-minimal-opcode-overloading-example=20
> >> with a test case (=20
> >> https://github.com/derickr/php-minimal-opcode-overloading-example/blob=
/master/tests/test.php=20
> >> ) that shows that something is looping in executing opcodes, as the=20
> >> HANDLE_EXCEPTION iirc doesn't advance to the next opline. I believe=20
> >> this is a recent enough change, as it only started happening after=20
> >> I upgraded from about RC1 to latest master.
> >>=20
> >> Would you care to have a look?
> >>=20
> > This is introduced by a fix made by Bob,=20
> > https://github.com/php/php-src/commit/808f62bb=20
> > <https://github.com/php/php-src/commit/808f62bb>
> >=20
> > Bob, I am going to revert this for now, since you didn't include a=20
> > test script to show where the problem was, I am not sure why you=20
> > made this?
>
> I didn't add any test case as we don't have any APIs in php-src using=20
> that user_opcode handler. I discussed the change back then with Dmitry=20
> and committed with his review.
>=20
> It concretely broke uopz which might throw an exception itself. And in=20
> turn we realized that for integrity we need to ensure that opline =3D=3D=
=20
> EX(opline) else we'll end up with different behavior in global=20
> register builds and normal builds.
>=20
> In general, you should not overload ZEND_HANDLE_EXCEPTION (if you need=20
> to, have a special handling for it, but never directly dispatch to=20
> it). It is quite special being the only opcode actually allowing=20
> EG(exception) to be non-NULL at the start of it.
>=20
> You are doing an #ifdef ZTS to exempt it=E2=80=A6 why don't you always ex=
empt=20
> it?

Even if I do (like I've just pushed into the extension), the test still=20
fails because the code loops. So you did break something.

cheers,
Derick
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