g++ warning: xxx does not declare anything

I see these warnings when building Trinity packages. They are non destructive warnings, the packages still build. I'm not a C++ guru but a quick browsing around the web indicates that this warning probably indicates sloppy code. Some examples: tdegraphics/kooka/thumbview.h:57: warning: declaration 'class KIO::PreviewJob' does not declare anything tdenetwork/kopete/libkopete/ui/metacontactselectorwidget.h:26: warning: declaration 'class Kopete::MetaContact' does not declare anything amarok/amarok/src/metadata/rmff/rmff.h:281: warning: declaration 'class TagLib::AudioProperties' does not declare anything Quality and robustness are always high on my priorities with Trinity. Should we address these warnings? If yes, then how can C++ newbies like me help with patching? That is, what is the appropriate fix for those warnings? Darrell