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To: "'Nikita Popov'" <nikita.ppv@gmail.com>,
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	"'Dmitry Stogov'" <dmitry@zend.com>
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Date: Mon, 29 Jun 2015 09:49:01 +0200
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Subject: RE: [PHP-DEV] Allow exceptions in __toString()
From: anatol.php@belski.net ("Anatol Belski")

Hi Nikita,

> -----Original Message-----
> From: Nikita Popov [mailto:nikita.ppv@gmail.com]
> Sent: Thursday, June 25, 2015 2:53 PM
> To: PHP internals; Dmitry Stogov
> Subject: [PHP-DEV] Allow exceptions in __toString()
>=20
> Hi internals!
>=20
> Currently it's not possible to throw an exception from __toString() - =
instead you
> will get a (real) fatal error. This is becoming more and more =
problematic as time
> goes on, e.g. with PHP 7 an exception can be triggered as a result of =
a VM error
> or even a parse error.
>=20
> I'd like to lift this restriction. A patch can be found here:
> https://github.com/php/php-src/pull/1364
>=20
> Apart from allowing exceptions, the patch also converts two leftover
> recoverable fatal errors relating to __toString() into Error =
exceptions.
>=20
> Furthermore the patch makes sure that we correctly (i.e. without leaks =
and
> without superfluous notices or other side-effects) handle __toString() =
exceptions
> in the engine. This includes concatenation and interpolation, but also =
things like
> writing $foo->$object or ${$object}.
> zend_parse_parameters() and Fast ZPP also deal with exceptions =
correctly.
>=20
> However what it doesn't do, and what I wouldn't consider feasible to =
do, is
> ensure that every single string conversion in library functions is =
exception safe.
> Personally I don't think this is a blocking issue, as the worst that =
can happen is
> usually an additional superfluous warning to be thrown, or something =
similar. If
> cases like this turn up, we can specifically target them.
>=20
> It should also be noted that whatever issues with exceptions-safety =
may remain,
> they already exist now (plus those the patch fixes), because the two
> aforementioned recoverable fatal errors can be converted to exceptions =
(and
> anyone doing blanket ErrorException conversions will do this).
>=20
> So basically the question here is, is this partial solution acceptable =
for us?
>=20
Given the expressed concerns, despite the change itself is a good thing =
when working properly, IMHO we shouldn't urge it into 7.0. If having it =
now can lead to subtle improper behavior and even worse bugs, preferable =
were to have a complete patch in 7.1.

Regards

Anatol