ldb bug fixes

[Adrian Cochrane]

Sorry, slight tidyup to those patches.

On Fri, Dec 4, 2015 at 3:54 PM, Adrian Cochrane 
<adrianc at catalyst.net.nz> wrote:
> Now I've got two working patches to propose to Samba, the first is 
> the one which fixes LDB to be able to handle empty messages in the 
> database. The second depends on it and would make that sort of issue 
> more obvious in the future. Please review
> 
> On Fri, Dec 4, 2015 at 10:03 AM, Adrian Cochrane 
> <adrianc at catalyst.net.nz> wrote:
>> It seems the patch for fixing error propagation is failing some 
>> tests. Please hold on that one.
>> 
>> I'm still happy with the patch for fixing handling of empty LDB 
>> messages (attached for clarity).
>> 
>> On Thu, Dec 3, 2015 at 2:29 PM, Adrian Cochrane 
>> <adrianc at catalyst.net.nz> wrote:
>>> Since the symptoms of the big I fixed in more previous patch were 
>>> incorrect, here's a patch which corrects the error propagation in 
>>> LDB.
>>> 
>>> On Wed, Dec 2, 2015 at 4:31 PM, Adrian Cochrane 
>>> <adrianc at catalyst.net.nz> wrote:
>>>> Another update, realized that if I'm allocating empty arrays it's 
>>>> probably useful still to check it for null.
>>>> 
>>>> On Thu, Nov 26, 2015 at 4:45 PM, Adrian Cochrane 
>>>> <adrianc at catalyst.net.nz> wrote:
>>>>> Updated patch per Andrew's comments.
>>>>> 
>>>>> On Wed, Nov 25, 2015 at 10:56 AM, Andrew Bartlett 
>>>>> <abartlet at samba.org> wrote:
>>>>>> On Mon, 2015-11-23 at 14:35 +1300, Adrian Cochrane wrote:
>>>>>>>  It turns out that wouldn't be an easier fix because
>>>>>>>  /lib/talloc/talloc_guide.txt specifically states:
>>>>>>>  >   talloc_realloc(context, ptr, type, 0) ==> talloc_free(ptr);
>>>>>>> 
>>>>>>>  However I did take your advice and incorporated it into this 
>>>>>>> updated
>>>>>>>  patch.
>>>>>> 
>>>>>> I think this, but with an error check on
>>>>>> msg->elements = talloc_array(msg, struct ldb_message_element, 0);
>>>>>> 
>>>>>> would be the correct solution.
>>>>>> 
>>>>>> LDB entries with zero attributes are vanishingly rare, but 
>>>>>> asking for
>>>>>> zero attributes is common, as is asking only for attributes that 
>>>>>> don't
>>>>>> exist.  We may post-process the ldb_message to add a generated
>>>>>> attribute later, and we should have a zero-length array to do 
>>>>>> that on.
>>>>>> 
>>>>>> This also follows the principle of least supprise from the 
>>>>>> current
>>>>>> code, which always returned an array the same length as the 
>>>>>> database
>>>>>> object (ie, always non-NULL, even with num_elements == 0)
>>>>>> 
>>>>>> Thanks,
>>>>>> 
>>>>>> Andrew Bartlett
>>>>>> 
>>>>>> --
>>>>>> Andrew Bartlett
>>>>>> https://samba.org/~abartlet/
>>>>>> Authentication Developer, Samba Team         https://samba.org
>>>>>> Samba Development and Support, Catalyst IT
>>>>>> https://catalyst.net.nz/services/samba
>>>>>> 
>>>>>> 
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