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Date: Sat, 9 Feb 2013 16:47:35 +0100
Message-ID: <CAEZPtU7wNj3GDD6GbLkZ-6KRAV_62Hj5QYzGiD7kLObtEbfEmg@mail.gmail.com>
To: Remi Collet <remi@fedoraproject.org>
Cc: PHP Internals <internals@lists.php.net>
Content-Type: text/plain; charset=ISO-8859-1
Subject: Re: [PHP-DEV] double val to long val conversion issue
From: pierre.php@gmail.com (Pierre Joye)

hi Remi

On Sat, Feb 9, 2013 at 4:10 PM, Remi Collet <remi@fedoraproject.org> wrote:
> About
> http://git.php.net/?p=php-src.git;a=commitdiff;h=79956330fe17cfd5f60de456497541b21a89bddf
> (For now, I have reverted this fix)
>
> Here some explanations.
>
> LONG_MAX is 9223372036854775807 (0x7fffffffffffffff)
> double representation of LONG_MAX is 9223372036854775808
>
> (d > LONG_MAX) is evaluated in double space.
> So is false for double which have the same value than (double)LONG_MAX.
>
> So, for (double)LONG_MAX the cast used is
>         (long)d
>
> 9223372036854775807 on ppc64
> 9223372036854775808 on x86_64 (gcc without optimization)
> 9223372036854775807 on x86_64 (gcc -O2)
>
> PHP expected value is 9223372036854775808
> (Btw, I don't understand why PHP, build on x86_64, with -O2, gives the
> good result, some environment mystery)
>
> Obviously, we could have different result on different platform,
> compiler, architecture.
>
> I will be very interested by result on other platform (mac, windows),
> compiler (Visual C), architecture.
>
> If we switch to the unsigned cast:
>         (long)(unsigned long)d;

> Any comments ?

IIRC, on windows/visualC, no matter if it is x86 or x64, long is
always 32bits, so it won't change the size of long.


Cheers,
--
Pierre

@pierrejoye