RE: [PHP-DEV] Allow exceptions in __toString()

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() > > Hi internals! > > 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. > > I'd like to lift this restriction. A patch can be found here: > https://github.com/php/php-src/pull/1364 > > Apart from allowing exceptions, the patch also converts two leftover > recoverable fatal errors relating to __toString() into Error exceptions. > > 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. > > 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. > > 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). > > So basically the question here is, is this partial solution acceptable for us? > 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