Re: Connecting to DBus socket without specifying bus_name

[Ian Arkver <ian arkver dev gmail com>]

On 03/02/16 01:31, Gerlof Fokkema wrote:
> Hello mailing list,
>
> I'm trying to use the glibmm interface to connect to the PulseAudio 
> DBus socket.
> So far, I've managed to connect to the DBus Session bus and retrieve 
> the socket address, and I've also managed to set up a connection to 
> that DBus socket.
>
> Source is here:
> https://github.com/gfokkema/equalizer/blob/master/src/pa-equalizer.cpp
>
> I'm having trouble calling DBus methods on the PulseAudio DBus socket,
> because of what I think is a bug in the glibmm bindings.
>
> https://github.com/gfokkema/equalizer/blob/master/src/pa-equalizer.cpp#L52
> ---------------------------------------------------------------------------------------------------
> auto sinks_result = this->conn->call_sync (
> "/org/pulseaudio/equalizing1",
> "org.freedesktop.DBus.Properties",
> "Get",
> parameters,
> "org.PulseAudio"
> );
>
> There is a QTPython application that also connects to this socket, but 
> it leaves the busname empty
> (link: 
> https://github.com/mkbosmans/pulseaudio/blob/master/src/utils/qpaeq#L229).
> Calling this method without specifying bus_name also works when using 
> glib, allowing the result to be converted glibmm.
> See branch develop on the same git repository for example.
>
> Am I correct in my understanding that because this is a standalone 
> DBus socket,
> the busname can be empty?
> And if so, why doesn't glibmm allow the busname to be 0 or NULL, while 
> the documentation does say that is acceptable input?
>
> When I change the bus_name, "org.PulseAudio" to NULL, my program 
> crashes with:
> # ./project
> > terminate called after throwing an instance of 'std::logic_error'
> > what(): basic_string::_M_construct null not valid
> > Aborted (core dumped)
>
>
> Thanks in advance,
>
> Gerlof Fokkema

This looks similar to the DBus::Connection::signal_describe problem from 
last September which required a patch from Murray to fix...

https://git.gnome.org/browse/glibmm/commit/?id=ece1463f6d796c7c74da1e9d37a4e69904a9706e

Regards,
Ian.