Date: Sun, 18 Mar 2012 19:32:04 -0700 From: Tim Kientzle <tim@kientzle.com> To: Jason Hellenthal <jhellenthal@dataix.net> Cc: svn-src-stable@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org, Eitan Adler <eadler@FreeBSD.org>, svn-src-stable-8@FreeBSD.org Subject: Re: svn commit: r233147 - stable/8/lib/libc/string Message-ID: <264991E4-B083-4E61-9337-E5882DED66C3@kientzle.com> In-Reply-To: <20120319021724.GC13456@DataIX.net> References: <201203190127.q2J1RtgB044557@svn.freebsd.org> <20120319015203.GB13456@DataIX.net> <CAF6rxgkhiznBRU04%2Bc%2BDPdBj9Omg03SqeSd9-0Ct-FfxAVm95g@mail.gmail.com> <20120319021724.GC13456@DataIX.net>
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On Mar 18, 2012, at 7:17 PM, Jason Hellenthal wrote: > > > On Sun, Mar 18, 2012 at 09:58:12PM -0400, Eitan Adler wrote: >> On Sun, Mar 18, 2012 at 9:52 PM, Jason Hellenthal >> <jhellenthal@dataix.net> wrote: >>> >>> >>> On Mon, Mar 19, 2012 at 01:27:55AM +0000, Eitan Adler wrote: >>>> Author: eadler >>>> Date: Mon Mar 19 01:27:55 2012 >>>> New Revision: 233147 >>>> URL: http://svn.freebsd.org/changeset/base/233147 >>>> >>>> Log: >>>> MFC r232503: >>>> POSIX mandates that swab do nothing when len < 0 >>>> >>>> PR: 140690 >>>> Approved by: cperciva >>>> >>>> Modified: stable/8/lib/libc/string/swab.c >>>> ============================================================================== >>>> --- stable/8/lib/libc/string/swab.c Mon Mar 19 01:27:30 2012 (r233146) >>>> +++ stable/8/lib/libc/string/swab.c Mon Mar 19 01:27:55 2012 (r233147) >>>> @@ -45,6 +45,8 @@ swab(const void * __restrict from, void >>>> int n; >>>> char *fp, *tp; >>>> >>>> + if (len <= 0) >>>> + return; >>> >>> Does this not test to see if it is also equal to 0(zero) ? >>> >>> If I understand the above statement "POSIX mandates that swab do nothing >>> when len < 0" then the above code should be exactly that ... and not >>> testing whether it is equal to zero... >> >> If the code doesn't check for len <= 0 then it will do something. >> > > To my understanding of the specification it should only return if len is > negative... 0 is not a negative number. From POSIX: > The swab() function shall copy nbytes bytes… This implies that it does nothing when the argument is zero. The check for <= 0 is a performance optimization; otherwise the code will do nothing in a more expensive fashion. > If nbytes is negative, swab() does nothing. This states that it does nothing when the argument is less than zero. So the change is correct; it covers both cases. Tim
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