Re: [PATCH] Use offsetof instead of magic number in scandir()

[Sebastian Huber <sebastian dot huber at embedded-brains dot de>]

On 03/28/2013 02:54 PM, Corinna Vinschen wrote:
> On Mar 28 14:36, Sebastian Huber wrote:
> > On 03/28/2013 01:42 PM, Corinna Vinschen wrote:
> > > On Mar 28 12:44, Sebastian Huber wrote:
> > > > > On 03/28/2013 12:17 PM, Corinna Vinschen wrote:
> > > > > > > Shouldn't we better use the upstream version as used in FreeBSD and
> > > > > > > OpenBSD?
> > > > > > >
> > > > > > >    #define DIRSIZ(dp)                                                      \
> > > > > > >            ((sizeof(struct dirent) - sizeof(dp)->d_name) +                 \
> > > > > > > 	      (((dp)->d_namlen + 1 + 3) &~ 3))
> > > > >
> > > > > I have problems to understand this expression.  What is
> > > > > "sizeof(dp)->d_name"? I think this looks like a hand-crafted
> > > > > offsetof variant.
> > > sizeof(dp)->d_name is sizeof((dp)->d_name), but without the lexically
> > > unnecessary parens.  I was just thinking that using the upstream
> > > version has the advnatage to use easier comparable code, given that
> > > our scandir.c is the BSD version anyway.
> >
> > Ok, this makes sense.  Should I use the FreeBSD version of DIRSIZ()
> > including its formatting?
> >
> > http://svnweb.freebsd.org/base/head/lib/libc/gen/scandir.c?revision=202693&view=markup
> >
> > It seems that the scandir() implementations diverged a bit.  In
> > Newlib we have this bugfix:
> >
> > commit c7ec1406e5abb6f1ec6363e1d13061934c1746e9
> > Author: Jeff Johnston <jjohnstn@redhat.com>
> > Date:   Mon Nov 24 20:42:33 2008 +0000
> >
> >      2008-11-24  Joel Sherrill <joel.sherrill@oarcorp.com>
> >
> >              * libc/posix/scandir.c: Fix memory leaks.
> >
> > Maybe we should report this to the BSDs.
>
> OpenBSD as well as FreeBSD have both fixed this issue, albeit slightly
> different from our version.

Yes, they fixed this bug ten years earlier:

http://svnweb.freebsd.org/base/head/lib/libc/gen/scandir.c?r1=39327&r2=40013

FreeBSD also changed the comparison function to ensure POSIX 2008 conformance:

http://svnweb.freebsd.org/base?view=revision&revision=202556

This is a difference to Newlib.

--
Sebastian Huber, embedded brains GmbH

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