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.