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  1. Qt
  2. QTBUG-98770

QList<T>::count(const T&) triggers undefined behavior sanitizer when list is empty

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    • 6855b80eae (qt/tqtc-qtbase/6.3)

    Description

      This minimal example triggers the UndefinedBehaviorSanitizer:

      QList<int> list;
list.count(2)

      Output from UndefinedBehaviorSanitizer (clang 12.0.0)

      /.../include/QtCore/qlist.h:198:52: runtime error: reference binding to null pointer of type 'const int'
    #0 0x5ac304 in QList<int>::const_iterator::operator*() const /.../include/QtCore/qlist.h:198:45
    #1 0x5797e8 in long long QList<int>::count<int>(int const&) const /.../include/QtCore/qlist.h:524:38

SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /.../include/QtCore/qlist.h:198:52 i

      We discovered this in our test suite, when trying to migrate to Qt 6.2.

      Attachments

        For Gerrit Dashboard: QTBUG-98770
        # Subject Branch Project Status CR V
        383718,4 QList::count(T): remove the &* hack on iterators dev qt/qtbase Status: MERGED +2 0
        383752,2 QList::count(T): remove the &* hack on iterators 6.2 qt/qtbase Status: MERGED +2 0

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            thiago Thiago Macieira
            frichter Florian Richter
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            Dates

              Created:
              Updated:
              Resolved:

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