Hi, On Monday 30 November 2009 11:07:29 Uwe Rathmann wrote: > Olivier Goffart wrote: > > I would like to add that using a floating point type as a key of a QHash > > might be dangerous as there will be == comparison on floating point type, > > which might not work well due to rounding issue > > The Qwt code is completely uninterested in hashing (or sorting) of doubles. > It only uses a simple QList<double> to store doubles for its values. > > > To my knowledge, Qt never had a qHash function for floating point types. > > I just verified it by grepping the diff between Qt 4.5 and Qt 4.6 > > For Qt <= 4.2 I had to add a dummy implementation of qHash<double> to the > Qwt headers. After reporting the bug to the TrollTech support the problem > was gone in Qt 4.3. Seems like this ( or a similar ) problem has been > reintroduced in Qt 4.6. > > > To my knowledge, Qt never had a qHash function for floating point types. > > I just verified it by grepping the diff between Qt 4.5 and Qt 4.6 > > I didn't check the QTL code, but I guess the code in qhash.h(875) is not > instantiated by the compiler in Qt 4.3 - Qt 4.5 for lists, that are never > sorted ? > > Uwe > > PS: It seems to be Windows only - I never saw problems with qHash on Linux.
I think this is because buggy compilers on windows instantiate the entire templated class even though some of the template functions are never called. gcc for example only instantiates the functions that are actually required. Sean _______________________________________________ Qt4-preview-feedback mailing list [email protected] http://lists.trolltech.com/mailman/listinfo/qt4-preview-feedback
