On Tue, 3 Dec 2019 at 20:09, Thiago Macieira <thiago.macie...@intel.com> wrote: > > On Monday, 2 December 2019 18:53:14 PST Ramakanth Kesireddy wrote: > > We got below errors in Qt 5.13 using C++ QWidgets while running static code > > analysis withKlocwork: > > > > 1)Address of a local variable is returned via return statement expression > > 'QStringBuilder<QStringBuilder<const char*,QString>,const char[2]>(a, > > &b).b'. > > 2)Address of a local variable is returned via return statement expression > > 'QStringBuilder<QStringBuilder<const char*,QString>,const char[2]>(a, &b).b' > > 3)Address of a local variable is returned via return statement expression > > 'QStringBuilder<const char[2],QString>(&a, b).a'. > > > > pointing to the below source @ > > https://github.com/qt/qtbase/blob/dev/src/corelib/text/qstringbuilder.h > > > > template <typename A, typename B> > > QStringBuilder<typename QConcatenable<A>::type, typename > > QConcatenable<B>::type> > > operator%(const A &a, const B &b) > > { > > return QStringBuilder<typename QConcatenable<A>::type, typename > > QConcatenable<B>::type>(a, b); > > } > > > > We are concatenating two QStrings using % which might lead to the above > > errors: > > For eg: eventString = eventString % eventState > > > > Do you recommend to use QString(%1%2").arg( eventString ).arg( eventState ) > > instead to resolve above errors or ignore the Klocwork errors reported? > > No, there's no need. QStringBuilder works just fine and has been working for > over 10 years. Either there's a problem somewhere in your code that you didn't > show to us or it s a Klocwork false positive.
To me it seems that QStringBuilder is broken. 10 years ago there was no C++11, no auto. QStringBuilder *worked* just fine, but not anymore. > Hint: do not use "auto" to detect the type when QStringBuilder is active. Hint: don't tell C++ programmers that by using Qt you cannot use C++ features as you wish. > Don't write: > auto str = a + b; > instead, write: > QString str = a + b; IMHO, it is legit to write code like: const QUrl url(urlString); const auto appId = url.host() + "." + url.path().mid(1); doSomeThing(appId); // void doSomeThing(const QString &stuff); Yet it results in crashes, apparently because of QStringBuilder holding references to temporary implicitly shared Qt object. I would expect QStringBuilder to somehow grab a reference to this implicitely shared object (eg. by incrementing a ref counter). AFAIU, QT_USE_QSTRINGBUILDER is a dangerous build option, don't use it. I honestly cannot accept that Qt is dictating me how to write C++ code because something is broken in Qt and the Qt people refuse to ack it. Please prove me wrong. Chris. NB: That's quite a perfect timing. The problem described above was reported to me yesterday evening, and this morning i saw this email thread. _______________________________________________ Interest mailing list Interest@qt-project.org https://lists.qt-project.org/listinfo/interest
