CWG Issue 491 (original) (raw)

This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 117a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2025-04-13

491. Initializers for empty-class aggregrate members

Section: 9.5.2 [dcl.init.aggr]Status: CD1Submitter: Nathan SidwellDate: 15 Dec 2004

[Voted into WP at April, 2007 meeting.]

The current wording of 9.5.2 [dcl.init.aggr] paragraph 8 requires that

An initializer for an aggregate member that is an empty class shall have the form of an empty initializer-list {}.

This is overly constraining. There is no reason that the following should be ill-formed:

struct S { };
S s;
S arr[1] = { s };

Mike Miller: The wording of 9.5.2 [dcl.init.aggr] paragraph 8 is unclear. “An aggregate member” would most naturally mean “a member of an aggregate.” In context, however, I think it must mean “a member [of an aggregate] that is an aggregate”, that is, a subaggregate. Members of aggregates need not themselves be aggregates (cf paragraph 13 and 11.9.2 [class.expl.init]); it cannot be the case that an object of an empty class with a user-declared constructor must be initialized with {} when it is a member of an aggregate. This wording should be clarified, regardless of the decision on Nathan's point.

Proposed resolution (October, 2005):

This issue is resolved by the resolution ofissue 413.