Hi,
I've been developing a Qt oriented clang compiler plugin called clazy [1]. It has about 50 custom checks/warnings for common Qt and C++ mistakes. I would like to propose clazy to be used to sanitize API of new Qt modules. Of course, only a few of the 50 checks are relevant to API, so I will only talk about those. ** Checks that can find bugs ** * clazy-copyable-polymorphic polymorphic copyable classes are usually vulnerable to slicing [2] The cases I found were either real bugs or easily fixable by adding Q_DISABLE_COPY. * clazy-rule-of-two-soft Finds when you're calling the compiler generated copy-ctor of a class that has a user-defined assign operator (and vice-versa). You'll want to write both, or none. I've found many bugs where one of them was missing (where the copy-ctor didn't have the same behavior as the assign- operator). In most cases you can simply remove the user defined methods and let the compiler generate them. * clazy-rule-of-three Either implement all 3 dtor, copy-ctor and assign-op or none of them. This is my favorite as it finds many bugs which are easy to fix. It's very common to have a class that is holding a resource and frees it in the DTOR, but if that class gets copied then two DTORs might run, freeing the resource twice, which might crash or misbehave the app. See for example https://codereview.qt-project.org/#/c/151488/ , QBasicTimer is copyable, but when a copy is destroyed it stops both timers. Also common is copying a class that has a d-pointer and getting a crash when both DTORs are run because you forgot the copy-ctor and assign-op. So either implement the copy-ctor and assign-op too, or use Q_DISABLE_COPY, or in the majority of cases, just remove your DTOR if it doesn't do any work. * mutable-container-key QMap or QHash having a key that can be modified by external factors (like QPointer) ** Nice to haves (don't find real bugs but are related to performance) ** * clazy-function-args-by-ref Pass big or non-trivial types (so copy-ctor and dtor don't get called) by const-ref * clazy-missing-typeinfo Types used in containers but missing a Q_DECLARE_TYPEINFO * clazy-qenums: Use Q_ENUM instead of Q_ENUMS * clazy-missing-qobject-macro missing a Q_OBJECT macro ** Debatable ** * clazy-function-args-by-value Pass small and trivial types by value Thanks for reading. [1] https://github.com/KDE/clazy [2] https://en.wikipedia.org/wiki/Object_slicing Regards, -- Sérgio Martins | sergio.mart...@kdab.com | Senior Software Engineer Klarälvdalens Datakonsult AB, a KDAB Group company Tel: Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322) KDAB - The Qt Experts _______________________________________________ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
