[Development] qDebug, qWarning, qCritical, qFatal in Qt source code
Hi, I would like to know if there are any guidelines about using qDebug and friends in Qt source code? Recently I had to remove qWarning statements from a submit (for very plausible reasons), but a quick search through qtbase revealed a lot of qWarning statements. So are there any rules of thumb? Cheers, Kurt ___ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
Re: [Development] qDebug, qWarning, qCritical, qFatal in Qt source code
On 3 May 2014 11:28, Kurt Pattyn pattyn.k...@gmail.com wrote: Hi, I would like to know if there are any guidelines about using qDebug and friends in Qt source code? Recently I had to remove qWarning statements from a submit (for very plausible reasons), but a quick search through qtbase revealed a lot of qWarning statements. So are there any rules of thumb? qWarning - the developer writing an app using Qt has made an error in their code that has lead to calling Qt with invalid values, for example connecting to a slot that does not exist. qDebug - when used in Qt itself, this is stuff to help with debugging of Qt. Users of Qt will often have Qt itself built without them, so don't rely on these messages to actually appear to people developing apps. qFatal - something is so screwed we cannot continue. Prints a message then aborts. qCritical - similar to the above but doesn't abort. Rich. ___ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
Re: [Development] qDebug, qWarning, qCritical, qFatal in Qt source code
On 3 May 2014 12:28, Kurt Pattyn pattyn.k...@gmail.com wrote: Recently I had to remove qWarning statements from a submit (for very plausible reasons), but a quick search through qtbase revealed a lot of qWarning statements. So are there any rules of thumb? Please also cf. the other thread about using categorized logging from within Qt. It's never good to use qDebug unconditionally, as that's useless information for the users. qWarning, qCritical, qFatal are fine to indicate a major problem, usually originating from user code or from some specific configuration issue. For instance a failing QObject::connect will print a warning through qWarning. Running a setuid binary will trigger a qFatal. Q_ASSERTs go through qFatal if they fail (but they're compiled out in release mode). qCritical is not really used in Qt. qFatal on its own will crash the program; qWarning / qCritical can be set to do the same by exporting QT_FATAL_WARNINGS=1. In programs we work on we strive to get 0 warnings by keeping that env variable set at all times. About qDebug: usually in Qt source code we had debug statements wrapped in macros: [snip] #ifdef ENGINE_DEBUG qDebug() Foo foo; #endif [snip] or: [snip] #ifdef ENGINE_DEBUG #define engineDebug qDebug #else #define engineDebug QT_NO_QDEBUG_MACRO #endif engineDebug() Foo foo; [snip] But for new code we should use categorized logging and its tests. Hope this helps, -- Giuseppe D'Angelo ___ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
