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Date: Mon, 24 Aug 2015 10:06:00 -0400
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To: Rowan Collins <rowan.collins@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=089e01161568053a34051e0f1e4a
Subject: Re: [PHP-DEV] Overflow checks and integral vars comparison
From: theanomaly.is@gmail.com (Sherif Ramadan)

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Hey Rowan,

Yup, I get it now. Sorry for the confusion.

I actually remember fixing a similar bug in pdo_sqlite a while back where
casting/translation between the two sizes caused such an issue. So I think
this would be pretty helpful.

On Sun, Aug 23, 2015 at 6:28 PM, Rowan Collins <rowan.collins@gmail.com>
wrote:

> On 22/08/2015 02:38, Sherif Ramadan wrote:
>
>> I see. So you're not actually doing overflow checks then? Because at the
>> point you'd be checking this zend_long or size_t it could have already
>> overflowed or wrapped. The subject may have misled me to understand
>> differently.
>>
>
> I think I understand the confusion: you are thinking of overflow as
> something which happens *within* a type based on some operation (addition,
> multiplication, etc).
>
> Anatol is talking about overflows which occur when casting *between*
> types: a value of 2^33 can safely be passed around as a 64-bit integer, no
> overflow has occurred; but attempting to cast it to a 32-bit integer will
> immediately overflow the 32-bit integer.
>
> Since many PHP extensions are wrappers around libraries which may only
> deal in 32-bit types, this cast is common, necessitating range checks like
> the ones proposed.
>
> Regards,
>
> --
> Rowan Collins
> [IMSoP]
>
>
>
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