Proposed resolution:

Modify Table 38 — Type property predicates for is_empty as follows:

T is a class type, but not a union type,is a non-union class type with no non-static data members other than, no unnamed bit-fields of non-zero length 0, no virtual member functions, no virtual base classes, and no base class B for which is_empty_v<B> is false.

[ 2016-10 Telecon ]

Should probably point at section 1.8 for some of this. Status back to 'Open'

[ 2016-10 by Marshall - this PR incorrectly highlighted changed portions ]

Modify Table 38 — Type property predicates for is_empty as follows:

T is a non-union class type with no non-static data members other than, no unnamed bit-fields of non-zero length 0, no virtual member functions, no virtual base classes, and no base class B for which is_empty_v<B> is false.

[ 2016-08 Chicago ]

Walter says: We want is_empty_v<S> to produce false as a result. Therefore, we recommend adoption of the first of the issue's suggestions.

Tuesday AM: Moved to Tentatively Ready

Previous resolution [SUPERSEDED]:

The 'Condition' for std::is_empty is listed as:

"T is a class type, but not a union type, with no non-static data members other than bit-fields of length 0, no virtual member functions, no virtual base classes, and no base class B for which is_empty<B>::value is false."

This is incorrect: there is no such thing as a non-static data member that is a bit-field of length 0, since bit-fields of length 0 must be unnamed, and unnamed bit-fields are not members (see [class.bit] p2).

It also means that classes such as:

struct S {
 int : 3;
};

are empty (because they have no non-static data members). There's implementation divergence on the value of is_empty<S>::value.

I'm not sure what the purpose of is_empty is (or how it could be useful), but if it's desirable for the above type to not be treated as empty, something like this could work:

"T is a class type, but not a union type, with no non-static data members other than, no unnamed bit-fields of non-zero length 0, no virtual member functions, no virtual base classes, and no base class B for which is_empty<B>::value is false."

and if the above type should be treated as empty, then this might be appropriate:

"T is a class type, but not a union type, with no (named) non-static data members other than bit-fields of length 0, no virtual member functions, no virtual base classes, and no base class B for which is_empty<B>::value is false."