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From Yann Ylavic <ylavic....@gmail.com>
Subject Re: What is the lifetime of apr_dbd_get_entry(...); result?
Date Mon, 02 Mar 2015 10:24:33 GMT
I meant to reply to all...

On Mon, Mar 2, 2015 at 11:23 AM, Yann Ylavic <ylavic.dev@gmail.com> wrote:
> On Mon, Mar 2, 2015 at 8:22 AM, Jan Kaluža <jkaluza@redhat.com> wrote:
>> On 02/04/2015 02:53 PM, Jan Kaluža wrote:
>>
>>> httpd's mod_authn_dbd module currently seems to expect that lifetime of
>>> apr_dbd_get_entry(...) result is the same as of the pool used in
>>> apr_dbd_get_row(...) function.
>
> It seems that the result's lifetime is really the one of the row, but
> mod_authn_dbd keep reading rows (sequentially) to cleanup the results
> (before exiting the loop, probably for connection keepalive purpose).
>
>>>
>>> But this is not a true for at least pgsql backend. Its get_entry
>>> function returns "return PQgetvalue(row->res->res, row->n, n);".
>>> Documentation for PQgetvalue says following:
>>>
>>> "One must explicitly copy the data into other storage if it is to be
>>> used past the lifetime of the PGresult structure itself."
>>>
>>> res->res is also freed in dbd_pgsql_get_row(...).
>
> Only the results out-of-range are freed (wrt asked rownum), but not
> the current one(s).
>
>>>
>>> Is that correct behaviour and httpd's mod_authn_dbd module should strdup
>>> the result, or is it apr_dbd, which should return result with expected
>>> lifetime?
>
> I think the fix is to be mod_authn_dbd only, APR looks correct here,
> and so is your patch.
>
> Regards,
> Yann.

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