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

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Date:	Mon, 6 Aug 2012 12:28:33 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Vasilyev <pavel@...linux.ru>
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

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.

Alan Stern

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