RFC: When to use #warning ?

[Friedrich W. H. Kossebau]

Hi all and especially the Kexi developers :)

the last days I spent some time to do little commits to decrease the currently 
quite high amount of warnings during a full build of Calligra. Most commits 
were some simple fixes like removing/hiding unused parameters/variables, so I 
felt free to skip any review process and to simply commit directly, noone 
might have had fun reviewing them anyway ;) Managed to cut around 6 % of the 
warnings (/me pats himself on the back), see
http://build.kde.org/job/calligra_master/warnings14/trendDetails/?
(those now and then slight increases in numbers are quite strange, anyone with 
an explanation for that?)

I guess everyone agrees that ideally there are no warnings at all, not only to 
quickly see new warnings due to own code changes. We build with warnings for a 
reason, don't we? But with still more than 1000 warnings e.g. in a 
build.kde.org build of master the motivation to prevent new warnings might be 
low, because what is 1 new warning due to sloppy coding if there are already 
1000, right? ;)
So I would like to continue the "game" where my/our highscore is the lowscore 
of warnings :) to give everyone the feeling that that extra line to ensure 
more code quality is worth it.

Now, a "grep '#warning' . -R | wc -l" tells there are at least 200 compiler 
warnings only due to #warning, from which 152 are in kexi/ and which most look 
to me rather like TODO comments.

Dear Kexi developers,
is there are real need for that, or would you possibly go with the idea that 
TODOs can also be noted as comments?
Advantages that I see:
* can be done with different keywords, to map to different kind of TODOs
* quickly collectable without a compiler/build run, using grep & Co.
* does not clutter the warnings which only the compiler can find out about

So what do you think about a general rule to be added to the Calligra coding 
style to avoid #warnings and use them just to emit real build/compiling 
related problems (like build condition checks that should not fail or 
similar)?

Of course I am willing to help with any patches needed to transform TODO 
#warnings into TODO comments :)

Now please your comments, hints, proposals!

Cheers
Friedrich