Movatterモバイル変換

Proposed resolution (February, 2017):

The resolution ofissue 2272 also resolvesthis issue.

Proposed resolution (November, 2016) [SUPERSEDED]:

Change 9.5.2 [dcl.init.aggr] paragraph 8 as follows:

If there are fewerinitializer-clauses in the list than there areelements in the aggregate, then eachEach non-variantelementof the aggregate that isnot explicitly initializedshall beisinitialized from its default member initializer(11.4 [class.mem]) or, if there is no default member initializer,copy-initializedfrom an empty initializer list(9.5.5 [dcl.init.list]).If the aggregate is a unionand the initializer list is empty, then

• if any union member has a default member initilizer, thatmember is initialized from its default member initializer;

• otherwise, the first member of the union (if any) iscopy-initialized from an empty initializer list.

[Example:...

[Adopted at the February/March, 2017 meeting.]

According to 9.5.2 [dcl.init.aggr] paragraph 15,

When a union is initialized with a brace-enclosed initializer, the bracesshall only contain aninitializer-clause for the first non-staticdata member of the union.

This would appear to preclude using{} as the initializer for aunion, which would otherwise have reasonable semantics. Is there a reasonfor this restriction?

Also, paragraph 7 reads,

If there are fewerinitializer-clauses in the list than there aremembers in the aggregate, then each member not explicitly initialized shallbe initialized from an empty initializer list (9.5.5 [dcl.init.list]).

There should presumably be special treatment for unions, so that onlya single member is initialized in such cases.

(See alsoissue 1460.)