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

[Pavel Vasilyev]

06.08.2012 20:28, Alan Stern ÐÐÑÐÑ:
> On Mon, 6 Aug 2012, Pavel Vasilyev wrote:
>
> > 06.08.2012 18:36, Alan Stern ÐÐÑÐÑ:
> > > 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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