From: Petr Baudis <pasky@suse.cz>
Date: Thu, 02 Nov 2006 11:04:50 GMT
Subject: Re: weird strncmp usage?
Message-ID: <20061102110450.GK20017@pasky.or.cz>
In-Reply-To: <45494D84.2060402@shadowen.org>

Dear diary, on Thu, Nov 02, 2006 at 02:44:36AM CET, I got a letter
where Andy Whitcroft <apw@shadowen.org> said that...
> Han-Wen Nienhuys wrote:
> > 
> > Hi,
> > 
> > the git source seems full of calls similar to
> > 
> >   strncmp (x, "constant string", 15)
> > 
> > is there a reason not to use something like
> > 
> >   int
> >   strxmp (char const *x, char const *y)
> >   {
> >     return strncmp (x, y, strlen (y));
> >   }
> > 
> > everywhere?
> 
> If you are doing these a _lot_ then there is a significant additional
> cost to using strlen on a constant string.
> 
> That said if you know its constant you can also use sizeof("foo") and
> that is done at compile time.  Something like:
> 
> #define strxcmp(x, y)	strncmp((x), (y), sizeof((y))

At least in the #define, reasonable compilers should optimize out
strlen("foo"). Hopefully as well if you would make strxmp() inlinable
though I'm not so sure there.

-- 
				Petr "Pasky" Baudis
Stuff: http://pasky.or.cz/
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$/=unpack('H*',$_);$_=`echo 16dio\U$k"SK$/SM$n\EsN0p[lN*1