Den 15-03-2016 kl. 14:07 skrev Marc Mutz:
Hi,No, this is not about the +1. QRect is internally represented as QPoint topLeft, bottomRight, which means it can hold rectangles for which width() and height(), returning ints, may overflow, e.g. QRect{{INT_MIN, INT_MIN}, QPoint{0, 0}} QRect{{INT_MIN, INT_MIN}, QPoint{INT_MAX, INT_MAX}} While these may seem like pathological cases that never occur in practice, the auto-test checks such rectangles, and if it didn't the next attacker would. It is therefore important to provide a fix width() and height(). There are two options I can see: qint64 width64() const; unsigned int width??() const; The first returns the result as a 64-bit quantitiy, preserving the negative widths of unnormalised rectangles, and never overflowing, but possibly penalises 32-bit platforms without 64-bit register support. The second still overflows for left() == INT_MIN, right() == INT_MAX, because of the +1 (don't highjack this thread, you have been warned! :), would only work on normalized rects, but doesn't require a 64-bit quantitiy. Opinions on which one to choose? One? The other? Both?
There is another option that doesn't mean a change of signature: Bound the result. So if the real result is > INT_MAX, return INT_MAX. Same for INT_MIN.
Yes, it's not the correct result, but I completely agree with you that it's a theoretical problem. As long as it's documented in the width() I really don't see the problem with this solution.
Bo Thorsen, Director, Viking Software. -- Viking Software Qt and C++ developers for hire http://www.vikingsoft.eu _______________________________________________ Development mailing list Development@qt-project.org http://lists.qt-project.org/mailman/listinfo/development
