QPixmap doesn't call detach() when load() is being called

In 4.6.2, QPixmap break the implicit sharing rule. I dosen't call detach() when load() is being called. The following code can produce this problem.

QPixmap pm1(":/image1.png");
QPixmap pm2(pm1);

pm1.load(":/image2.png");

pm1.save("output1.png");
pm2.save("output2.png");

after running this program, output1.png should be the same as image2.png and output2.png should be the same as image1.png, but now they are both image2.png