$ cat test.C
#include <QList>

int main(int argc, char** argv) {

  QList<int> a;
  a.append(1);
  a.removeFirst();
  return 0;
}

$ g++ -std=c++11 -Werror -Wextra -fPIC -I/usr/include/qt -I/usr/include/qt/QtCore -lQt5Core -o test test.C

In file included from /usr/include/qt/QtCore/QList:1,
                 from test.C:1:
/usr/include/qt/QtCore/qlist.h: In instantiation of ‘QList<T>::iterator QList<T>::erase(QList<T>::iterator) [with T = int]’:
/usr/include/qt/QtCore/qlist.h:353:55:   required from ‘void QList<T>::removeFirst() [with T = int]’
test.C:7:17:   required from here
/usr/include/qt/QtCore/qlist.h:536:12: error: implicitly-declared ‘QList<int>::iterator& QList<int>::iterator::operator=(const QList<int>::iterator&)’ is deprecated [-Werror=deprecated-copy]
  536 |         it = begin(); // implies detach()
/usr/include/qt/QtCore/qlist.h:239:16: note: because ‘QList<int>::iterator’ has user-provided ‘QList<T>::iterator::iterator(const QList<T>::iterator&) [with T = int]’
  239 |         inline iterator(const iterator &o) Q_DECL_NOTHROW : i(o.i){}
      |                ^~~~~~~~
cc1plus: all warnings being treated as errors