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

Andrew Gregory andrew.gregory.8 at gmail.com
Tue Jul 1 18:03:04 EDT 2014

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

I don't think keeping log messages in the event callback is worth the


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