What kind of magic does QString().setNum() do?

I agree with Blazecock Pileon that this smells like a bug. But, if you really want to convert signed to unsigned, this bit of JS trickery will do it: Input: -1413011644 >> 0 >>> 0 Output: 2881955652 JS's Number representation is strange to say the least. It's internally represented as a floating-point number, except when https://developer.mozilla.org/en/JavaScript/Reference/Operators/Bitwise_Operators when it's represented as a signed integer. Except in the case of >>>, when it's an unsigned integer. So you can abuse the bitwise operators to convert your Number to a signed integer, then an unsigned integer.

From the http://doc.trolltech.com/4.2/qstring.html#setNum: The base is 10 by default and must be between 2 and 36. For bases other than 10, n is treated as an unsigned integer. Since you're working in base 10, this implies you can give a signed value. Perhaps you've discovered a bug, if your signed value is being printed as its unsigned equivalent. You might want to contact the devs for support, in that case.

I neglected to mention that 'id' is defined as quint32, so it is indeed unsigned. It is less than helpful that when I print it to stdout it comes out as signed, which led to the confusion. Applying zsazsa's trickery to my code solves the problem. Thank you.

The shift hack will work, but mathematically http://www.google.com/search?q=2%5E32+-1413011644 if you want something that's easier for people too understand if they ever look through your code.

when I print it to stdout it comes out as signed How are you printing it to stdout? It's possible that that's where the reinterpretation from uint32 to sint32 is happening.