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Date: Thu, 17 Aug 2017 18:03:27 +0300
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Subject: Re: [Request][Discussion] Double value as array key improvement
From: andrew.nester.dev@gmail.com (Andrew Nester)

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> 13 =E0=E2=E3. 2017 =E3., =E2 21:39, Andrew Nester <andrew.nester.dev@gmail=
.com> =ED=E0=EF=E8=F1=E0=EB(=E0):
>=20
>=20
>=20
>> 11 =E0=E2=E3. 2017 =E3., =E2 15:53, Andrew Nester <newaltgroup@bk.ru> =ED=
=E0=EF=E8=F1=E0=EB(=E0):
>>=20
>>=20
>>> On Aug 11, 2017, at 2:10 PM, Andrew Nester <newaltgroup@bk.ru> wrote:
>>>=20
>>> Hello everyone!
>>>=20
>>> I was working on following request https://bugs.php.net/bug.php?id=3D750=
53 which resulted in following pull request https://github.com/php/php-src/p=
ull/2676
>>>=20
>>> The problem here is following: when we=92re using large numbers as array=
 index when adding new elements it could overwrite already existing value.
>>> Assume we have 2 indexes 5076964154930102272 and 99999999999999999999999=
9999999 with different value set for them.
>>>=20
>>> Because 999999999999999999999999999999 is larger than maximum long int n=
umber for 64-bit systems, it will be converted to double. (corresponding cod=
e 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 i=
nteger. (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=92ve got index equal to 507696415=
4930102272 and as a result - we=92re overwriting previously set value.
>>>=20
>>> My suggestion is following:
>>> 1) when double key is less than maximum possible long integer - convert i=
t to integer
>>> 2) if it=92s larger - convert it to string.
>>>=20
>>> That=92s what implemented in proposed PR.
>>>=20
>>> Another possible option is just to throw warning in this case (proposed b=
y Nikita Popov)
>>>=20
>>> I would happy to hear any feedback and suggestions about this solution.
>>> Thanks!
>>=20
>> Here is the alternative solution which emits E_WARNING in case of integer=
 array index overflow.
>> https://github.com/php/php-src/pull/2677
>=20
> My preferred solution is 2nd one (emitting warning) as it more obvious for=
 users, doesn't break previous behaviour.
>=20
> Cheers,
> Andrew

Hello internals!

I was working on solution for the problem of double to int conversion for ar=
ray 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!=

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