Question

I remember reading somewhere that Qt guarantees the size of some data types on supported platforms. Is it that int will be at least 32 bits everywhere, and qint32 will be exactly 32 bits everywhere? Or something else?

C++ guarantees that int will be at least 16 bits, and some Qt structures like QRect and QPoint use int internally. I’m developing an application where 32 bits is needed with those types, and I don’t want to have to duplicate their functionality so I can use a larger type.

Answer 1

The size of an integer type is up to the compiler. I don’t think there’s a guarantee that plain int will be of a precise size. But you can make sure you know it’s not what you want by adding this line to the beginning of your main():

if(sizeof(int) != 4) {
  throw std::runtime_error("int is not 32-bit");
}