Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:61445
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.217.170 as permitted sender)
MIME-Version: 1.0
Date: Thu, 19 Jul 2012 00:39:21 +0200
Message-ID: <CAF+90c-8CENDFSsF=D3ag1s5yvhWvuedUzjwmPPDbTTXyETk8g@mail.gmail.com>
To: PHP internals <internals@lists.php.net>
Content-Type: text/plain; charset=ISO-8859-1
Subject: Integer overflows on float to int casts
From: nikita.ppv@gmail.com (Nikita Popov)

Hi internals!

When a large floating point number is cast to an integer we currently
have very low-level C behavior (integer overflow and wraparound):

$ /c/php-5.4.1/php -r 'var_dump((int) 4000000000);'
int(-294967296)

$ /c/php-5.4.1/php -r 'var_dump((int) 6000000000);'
int(1705032704)

As a fun fact, if you do the same thing with a string float the number
if clipped instead of wrapped:

$ /c/php-5.4.1/php -r 'var_dump((int) "4000000000");'
int(2147483647)

This also applies to zend_parse_parameters. l arguments are wrapped, L
arguments are clipped.

In my eyes this kind of behavior has nothing to do in PHP. PHP is a
high-level language, it shouldn't exhibit low-level stuff like integer
overflows and wraparound.

I think that at least for zend_parse_parameters this should be
changed. Overflowing float parameters should not be accepted. Instead
throw the usual E_WARNING and return FAILURE.

I'm not sure though what one should do about the explicit (int) cast.
My preference would be to throw a notice and use the clipping
behavior.

Thoughts?

Nikita