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

[Sebastian Huber]

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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