[Development] Work on qDebug and friends - debug areas

[Olivier Goffart]

On Tuesday 24 January 2012 11:03:11 kai.koehne at nokia.com wrote:
> Hi,
> 
> One of the things still missing in the current debugging framework is to
> categorize messages by area: This would allow you to enable/disable e.g.
> debug messages for only one part of your app ...
> 
> KDE & kDebug
> 
> Here debug categories are basically ints, which have to be registered
> 'kdelibs/kdecore/kdebug.areas'. You can pass your specific as an argument
> to kDebug(..) et al., but usually you just set a define
> (KDE_DEFAULT_DEBUG_AREA).
> 
> + comparing int's is fast
> - one central registry needed for debug areas (no go for custom apps?)

May I suggest we use something like qHash("MyModule")
And ignore the fact that there are collisions. (you only would loose a bit 
granularity in rare occasions.)


> Log4cxx ...
> 
> Frameworks like log4cxx
> (http://www.360doc.com/content/09/0508/23/36491_3425784.shtml) that are
> modeled after log4j use free text to define areas. Also, the areas might be
> nested, so that "MyModule " includes "MyModule.Part" semantically, and you
> can do very fine grain adjustments on what exactly to log.
> 
> + Lots of flexibility
> - comparing strings is slow, chances that you mistype ...

you can reduce the mistype changes my using macro or static char*

How slow is it really, compared to the cost of streaming the different types 
to string and concatenating them?

Also qDebug will get disabled in release, right?