Windows, MSVC2010+: Warning C4718 with QMap when using /W 4

1>d:\5.0.2\include\qtcore\qmap.h(234): warning C4718: 'QMapNode<int,int>::destroySubTree' : recursive call has no side effects, deleting
1>d:\5.0.2\include\qtcore\qmap.h(332): warning C4718: 'QMapNode<int,int>::destroySubTree' : recursive call has no side effects, deleting
1>d:\test\main.cpp(8): warning C4718: 'QMapNode<int,int>::destroySubTree' : recursive call has no side effects, deleting
1>d:\test\main.cpp(17): warning C4718: 'QMapNode<int,int>::destroySubTree' : recursive call has no side effects, deleting

#include <QtCore/QCoreApplication>
#include <QtCore/QMap>

class Test
{
    public:
    Test() {}
    ~Test() {}
    QMap<int, int> m;
};

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    Test t;
    return a.exec();
}