On Thu, Aug 17, 2017 at 5:03 PM, Andrew Nester <andrew.nester....@gmail.com> wrote:
> > > > 13 авг. 2017 г., в 21:39, Andrew Nester <andrew.nester....@gmail.com> > написал(а): > > > > > > > >> 11 авг. 2017 г., в 15:53, Andrew Nester <newaltgr...@bk.ru> написал(а): > >> > >> > >>> On Aug 11, 2017, at 2:10 PM, Andrew Nester <newaltgr...@bk.ru> wrote: > >>> > >>> Hello everyone! > >>> > >>> I was working on following request https://bugs.php.net/bug.php? > id=75053 which resulted in following pull request > https://github.com/php/php-src/pull/2676 > >>> > >>> The problem here is following: when we’re using large numbers as array > index when adding new elements it could overwrite already existing value. > >>> Assume we have 2 indexes 5076964154930102272 and > 999999999999999999999999999999 with different value set for them. > >>> > >>> Because 999999999999999999999999999999 is larger than maximum long int > number for 64-bit systems, it will be converted to double. (corresponding > code here https://github.com/php/php-src/blob/master/Zend/zend_ > language_scanner.l#L1648) > >>> But when double value is used as array indexes, it is converted to > long integer. (f.e., code is here https://github.com/php/php- > src/blob/master/Zend/zend_execute.c#L1573) > >>> At this case it causes overflow and we’ve got index equal to > 5076964154930102272 and as a result - we’re overwriting previously set > value. > >>> > >>> My suggestion is following: > >>> 1) when double key is less than maximum possible long integer - > convert it to integer > >>> 2) if it’s larger - convert it to string. > >>> > >>> That’s what implemented in proposed PR. > >>> > >>> Another possible option is just to throw warning in this case > (proposed by Nikita Popov) > >>> > >>> I would happy to hear any feedback and suggestions about this solution. > >>> Thanks! > >> > >> Here is the alternative solution which emits E_WARNING in case of > integer array index overflow. > >> https://github.com/php/php-src/pull/2677 > > > > My preferred solution is 2nd one (emitting warning) as it more obvious > for users, doesn't break previous behaviour. > > > > Cheers, > > Andrew > > Hello internals! > > I was working on solution for the problem of double to int conversion for > array indices and would like to create an RFC for proposed solution - > emitting warning when integer overflow happens during double to int > conversion. > > Does it look like good idea? > > Thanks! Sounds good to me. Something you might want to consider is to also throw a warning if the floating point number is not an exact integer. For example allow a silent cast of 42.0 to 42, but throw a warning if 42.5 is used as an index (or worse, 42.999999999, in which case it likely isn't doing what the programmer thinks it's doing). Nikita
