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Date: Mon, 15 Aug 2011 11:48:18 +0800
Message-ID: <CAHMUw2ENKWjgQH_-eA4uP94yjw1pvQ50OoEUx+wZ5AmwhMfEoA@mail.gmail.com>
To: Laruence <laruence@php.net>
Cc: Rasmus Lerdorf <rasmus@php.net>, Stas Malyshev <smalyshev@sugarcrm.com>, 
	Derick Rethans <derick@php.net>, PHP Internals <internals@lists.php.net>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Subject: Re: [PHP-DEV] [VOTE]strn(case)cmp supporting a negative length as its
 third paramter
From: datibbaw@php.net (Tjerk Anne Meesters)

Hi,

Doesn't substr_compare() accomplish the same thing since 5.1.0?

The only thing I couldn't figure out is how to make it case
insensitive without specifying an explicit value to $length


Best,
  Tjerk

On Mon, Aug 15, 2011 at 11:18 AM, Laruence <laruence@php.net> wrote:
> Hi:
> =A0 compare to use substr, =A0 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)) {
>>>>> =A0 =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:
>>
>> =A0 if (substr("prefix_num", -3) =3D=3D "num") {
>> =A0 =A0 =A0 =A0echo "they have same suffix\n";
>> =A0 }
>>
>>
>> into:
>>
>> =A0 if (strncmp("prefix_num", "num", -3) =3D=3D=3D 0) {
>> =A0 =A0 =A0 =A0echo "they have same suffix\n";
>> =A0 }
>>
>> That doesn't seem like a big win to me.
>>
>> -Rasmus
>>
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>>
>
>
>
> --
> Laruence =A0Xinchen Hui
> http://www.laruence.com/
>
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>



--=20
--
Tjerk