Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:54604
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.220.170 as permitted sender)
MIME-Version: 1.0
Sender: laruence@gmail.com
In-Reply-To: <4E4843B0.70605@php.net>
References: <CABBJUpfez0_CKkiFSVVmYfxbF7H30Av2y9D1Nww6PE5v6dKPUw@mail.gmail.com>
	<CAM4sM9Hxn=2FJ4d51ozbKuGM4e3BMMUQ38WsEs27WAu919XSjg@mail.gmail.com>
	<CABBJUpdONFHHYpdr4RvxGRyJ13M9yONVzb-aSjx33QKziALkLA@mail.gmail.com>
	<CABBJUpeoDnuT7eXC6UzUFQni0V0zH_mivHiX=3j=UjCKJK-z7Q@mail.gmail.com>
	<CABBJUpdXUOjyWpXeRovNaFgDMQHfM5MkXXto+Rybej2u+W4xFw@mail.gmail.com>
	<alpine.DEB.2.02.1108141219470.4043@whisky>
	<CAH-PCH6_sTBGqCrCp-pgdi3DJfFX-3ZsvSr8ibbrOtKQP0qpTA@mail.gmail.com>
	<alpine.DEB.2.02.1108141359340.4043@whisky>
	<4E48121A.3090007@sugarcrm.com>
	<4E48134E.4030708@sugarcrm.com>
	<4E481695.6040900@php.net>
	<4E483804.7070009@sugarcrm.com>
	<4E484037.2080107@php.net>
	<4E4843B0.70605@php.net>
Date: Mon, 15 Aug 2011 11:18:33 +0800
Message-ID: <CABBJUpfmV23H2MgkCi60MeLN1dp9Qe+aJJj1y9F0GWfSXL_ygA@mail.gmail.com>
To: Rasmus Lerdorf <rasmus@php.net>
Cc: Stas Malyshev <smalyshev@sugarcrm.com>, Derick Rethans <derick@php.net>, 
	PHP Internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Subject: Re: [PHP-DEV] [VOTE]strn(case)cmp supporting a negative length as its
 third paramter
From: laruence@php.net (Laruence)

Hi:
   compare to use substr,   strncmp supporting negative lenght can
save a temp variable.

thanks

2011/8/15 Rasmus Lerdorf <rasmus@php.net>:
> On 08/14/2011 02:37 PM, Rasmus Lerdorf wrote:
>> On 08/14/2011 02:03 PM, Stas Malyshev wrote:
>>> Hi!
>>>
>>> On 8/14/11 11:40 AM, Rasmus Lerdorf wrote:
>>>> My main issue with changing strncmp/strncasecmp is that these are
>>>> currently exact mappings of the underlying libc functions. For people
>>>
>>> And why should anybody care? 99% of people using PHP never used a libc
>>> function and can hardly tell libc from gcc. If we can extend this
>>> function with useful functionality, nobody cares about what libc does.
>>>
>>>> For example, I could imagine people writing code along these lines:
>>>>
>>>> $len =3D strlen($user_data) - strlen($suffix);
>>>> if(!strncmp($user_data, $string, $len)) {
>>>> =C2=A0 =C2=A0 // do something
>>>> }
>>>
>>> Warning doesn't fix the bug - and unless you're in 0.0001% of the
>>> population that actually reads the logs daily and checks every message
>>> there it would be little to help you. We should have more useful
>>> functions, not more warnings. Warning won't make this code to work.
>>
>> I agree, however this change would potentially change the return value
>> of the function. Before it would warn and not match. Even if you never
>> saw the warning, at least length -1 would not give you a match. Now if
>> the user data happens to end with the right character we now have a
>> string match which is not at all what the code was written to do.
>
> Put more succinctly. Subtle BC breaks like this worry me. Any strncmp()
> call with a computed length where that length may in some cases go
> negative will now potentially return a match where it wouldn't before.
> This would be very hard to track down. And the reason for introducing
> this subtle BC break is so that you can rewrite:
>
> =C2=A0 if (substr("prefix_num", -3) =3D=3D "num") {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0echo "they have same suffix\n";
> =C2=A0 }
>
>
> into:
>
> =C2=A0 if (strncmp("prefix_num", "num", -3) =3D=3D=3D 0) {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0echo "they have same suffix\n";
> =C2=A0 }
>
> That doesn't seem like a big win to me.
>
> -Rasmus
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>



--=20
Laruence =C2=A0Xinchen Hui
http://www.laruence.com/