Regularly, I could reference limits.h to see what the max is for a certain type, like an int or long.
In Qt, there are types like qlonglong. Is there a header file and/or documentation that can be used in a similar way to manually or programmatically reference the limits of these types?
There's a high likelihood the Qt types distill down to one of the basic types for which numeric_limits are defined. Have you tried calling e.g., std::numeric_limits<qlonglong>::max()?
As MSalters points out, too, if the types are not builtin numeric_limits can still be specialized for them. If that were the case one would hope Qt would include them.
Take a look at the QtGlobal documentation.
For some of the non-obvious ones:
qlonglong - 64-bit
qptrdiff - 32-bit or 64-bit depending on platform
qreal - double (float on ARM architectures)
quintptr - unsigned 32-bit or 64-bit depending on platform
qulonglong - unsigned 64-bit
uchar, uint, ulong, ushort - convenience shorthand for unsigned types
来源：https://stackoverflow.com/questions/4788693/where-are-the-limits-for-qt-types