Forcing enum to be of unsigned long type

Question

Is it possible to force the underlying type of an enumeration to be unsigned long type? Thanks

Answer 1

In C++11 and higher, you can explicitly mention what type you want:

enum MyEnumeration: unsigned long {
   /* ... values go here ... */
};

This will allow you to explicitly control the underlying type.

In C++03, there is no way to force an enumerated type to have any particular underlying implementation. Quoth the C++03 spec, §7.2/5:

The underlying type of an enumeration is an integral type that can represent all the enumerator values defined in the enumeration. It is implementation-defined which integral type is used as the underlying type for an enumeration except that the underlying type shall not be larger than int unless the value of an enumerator cannot fit in an int or unsigned int. If the enumerator-list is empty, the underlying type is as if the enumeration had a single enumerator with value 0. The value of sizeof() applied to an enumeration type, an object of enumeration type, or an enumerator, is the value of sizeof() applied to the underlying type.

This is a pretty lax condition and says that not only can you not necessarily know the type, but because it's implementation-defined there's no guarantee that it even corresponds to one of the primitive types at all.