first stage to factoring and separate compiler warnings options to disable in goal to limit traces generate while compilation. In all cases, Clang >=8 give better results than GCC while parsing C++ syntax everywehere and reports less false positive than GCC. I recommend to switch to Clang to compile whole digiKam. Reports on the console are more human readable and canbe really considerate has true positive. The Clang -Wpedantic for ex, report real problem on C++ syntax. In oppposite, GCC -Wpedantic, report plenty false positive with qCdebug which transform compilation traces as a mess...