[pacman-dev] [PATCH v2 2/2] Update the question callback

[Olivier Brunel]

On 07/02/14 00:03, Andrew Gregory wrote:
> On 07/01/14 at 08:27pm, Olivier Brunel wrote:
>> On 07/01/14 06:56, Allan McRae wrote:
>>> On 29/06/14 21:35, Olivier Brunel wrote:
>>>> On 06/29/14 03:50, Allan McRae wrote:
>>>>> On 24/06/14 20:18, Olivier Brunel wrote:
>>>>>> On 06/24/14 08:14, Allan McRae wrote:
>>>>>>> On 26/05/14 01:30, Andrew Gregory wrote:
>>>>>>>> The earlier changes to the event callback have the same issue and also
>>>>>>>> give errors about using non-literal strings with vprintf:
>>>>>>>>
>>>>>>>>  testdb.c:53:11: error: format string is not a string literal
>>>>>>>>        [-Werror,-Wformat-nonliteral]
>>>>>>>>                  vprintf(event->fmt, event->args);
>>>>>>>>                          ^~~~~~~~~~
>>>>>>>
>>>>>>> BAH!   Why did gcc no see this?
>>>>>>>
>>>>>>> Unless someone comes up with something else, I'll do the revert soon.
>>>>>>
>>>>>> I can't think of another way to silence the warning, but there's a way
>>>>>> to "work around" it: instead of putting fmt & args inside
>>>>>> alpm_event_log_t, we put the resulting string (i.e. call pm_asprintf()
>>>>>> in alpm and send the resulting string in the event).
>>>>>>
>>>>>> No more false warnings then (but a malloc/free for each log event). I
>>>>>> can send a patch if you'd like.
>>>>>
>>>>> Can not do that.   Translations of messages happen in the front-end.
>>>>
>>>> um, no? Translations obviously happen in ALPM, the call to gettext
>>>> happens before calling _alpm_log(), so by then whether we send the
>>>> message to the front-end as a pointer to the full string, or a pointer
>>>> to a format string and a va_list, doesn't really matter.
>>>>
>>>> All the front-end does is decide whether or not (e.g. based on level),
>>>> and how, to show the message to the user.
>>>>
>>>> Or did I not understand what you meant at all?
>>>
>>> Some parts are, some are not (the prefixes).  Also, pm_asprintf is not
>>> available in the backend.
>>
>> I assume by prefixes you mean the front-end could add e.g. "warning:"
>> before the message itself? Then sure, that part would be translated in
>> the front-end, but I fail to see how getting the message as a string and
>> not a format string & va_list would change/break anything?
>>
>> Either way, the front-end has no idea what the message is, nor does it
>> care/do anything other than showing it to the user.
>>
>> (And pm_asprintf could simply be moved to util-common.c no?)
>>
>>> I am in favour of reverting the log callback as the solution here.
>>
>> I feel it's a little sad there isn't a way to silence this
>> false-positive warning, since this is really all it's about.
>>
>> I guess the log already had its own callback separated from events,
>> although looking at the history it seems more to be because the log_cb
>> was created first than for any actual reason, and "merging it" into
>> events was a good idea IMO.
>>
>> (Of course, if there's ever another event with such a generated
>> string/message, it'll have to be an event, and that'll make the log
>> stand out even more for no good reason...)
>>
>> I just think making it an event was a good thing, but I don't feel very
>> strongly about this, so I guess you could just revert to a separate log
>> callback -- though I'm curious what's the main motivation for favoring
>> this solution? Avoiding the malloc/free calls (A buffer could also be
>> used/printed into then, leaving the malloc only for extra-long messages) ?
> 
> Incorporating log messages into the event callback also silenced log
> messages when --print is used, including debug messages, which needs

I don't understand. The commit that introduced log messages as event,
that Allan will likely revert, shouldn't have changed anything in
how/when said messages are printed, only how they are sent to the
front-end (as in, which callback function is used).

Also, I just ran `pacman --debug -S --print pacman` and I see debug
messages just fine. So I'm not sure what you mean, could you tell me how
to reproduce it?

> to be fixed.  So, in order to keep it in the event callback you would
> have to:
> 
> * create a special case for the log event in the callback when --print is used

As said earlier, I don't see why a special case is needed/what was
broken here.

> * malloc the formatted string in the back-end solely for the purpose
>   of passing it to the front-end even if it will be ignored or could
>   have been printed directly without the malloc

True (although it could be printed to a buffer, but yes)

> * malloc a second copy of the string in the front-end whenever it's in
>   the middle of a progress bar

True, but in that case pacman always mallocs its own copy of the message
anyways, so nothing new here.

> 
> I don't think keeping log messages in the event callback is worth the
> hassle.
> 
> apg
>