@aha_1980 Thanks for your detailed answer to this thread!
First, I'm working on a software where users need to instantiate such large integers, that's the main motivation behind my contribution. I cannot estimate whether it'll be a rare use, I only know that we need it. And the fact is we don't have many options:
Inherit from QAbstractSpinBox and reimplement dirtily the needed methods, duplicating existing code from private parts of Qt that we don't have access to, or patch up code to make it works (not a really satisfying solution) Modify Qt source code and distribute it with the program (can be tedious to maintain tho) Modify Qt source code and integrate the changes (providing everyone with a clean new widget/feature)That being said, I am perfectly aware of the code duplication for I studied the QSpinBox code when implementing the QLongLongSpinBox. Hence I came to (quite) the same conclusion: using a qlonglong in place of the actual int for member variables. The main drawback of this would be the memory cost, I guess, so I was thinking of some kind of optimizations but I will have to consult people that know more about it.
That's where your mailing list comes in handy! So thanks again, I'm definitely going to ask questions there!