linux-kernel - Re: [linux-pm] [PATCH] ACPI: replace strlen("string") with sizeof("string") -1

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Message-ID: <50201156.30704@pavlinux.ru>
Date:	Mon, 06 Aug 2012 22:47:50 +0400
From:	Pavel Vasilyev <pavel@...linux.ru>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Pavel Machek <pavel@....cz>, Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>
Subject: Re: [linux-pm] [PATCH] ACPI: replace strlen("string") with sizeof("string")
 -1

06.08.2012 20:28, Alan Stern пишет:
> On Mon, 6 Aug 2012, Pavel Vasilyev wrote:
>
>> 06.08.2012 18:36, Alan Stern пишет:
>>> On Mon, 6 Aug 2012, Pavel Machek wrote:
>>>
>>>> On Thu 2012-07-26 21:39:38, Len Brown wrote:
>>>>> ...both give the number of chars in the string
>>>>> without the '\0', as strncmp() wants,
>>>>> but sizeof() is compile-time.
>>>>
>>>> What about introducing something like streq() to do this
>>>> automatically? This is ugly....
>>>>
>>>> #define streq(a, b) ... if (_buildin_constant(b)) ...
>>>>
>>>> ?
>>>>
>>>>> -	if (!strncmp(val, "enable", strlen("enable"))) {
>>>>> +	if (!strncmp(val, "enable", sizeof("enable") - 1)) {
>>>
>>> While you're at it, there's no point using strncmp when you know the
>>> length of one of the strings beforehand.  Just use memcmp, and don't
>>> subtract 1 from the sizeof value.
>>
>> http://www.gossamer-threads.com/lists/engine?do=post_attachment;postatt_id=41157;list=linux
>
> Interestingly, many (all?) of the changes in that patch are wrong
> because they don't try to match the terminating '\0'.  As a result,
> they will match against extensions of the target string as well as the
> target string itself.
>

strNcmp compare N bytes - http://lxr.linux.no/#linux+v3.5/lib/string.c#L270
memcmp compare N bytes  - http://lxr.linux.no/#linux+v3.5/lib/string.c#L651

-- 

                                                          Pavel.
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