CWG Issue 2171 (original) (raw)

This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 118e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2025-11-05

2171. Triviality of copy constructor with less-qualified parameter

Section: 11.4.5.3 [class.copy.ctor]Status: CD4Submitter: Jason MerrillDate: 2015-09-14

[Adopted at the June, 2016 meeting.]

Issue 1333 says that a defaulted copy constructor with a less-const-qualified parameter type than the implicit declaration is non-trivial. This is inconsistent with the usual pattern that whether a special member function is callable is separate from whether it is trivial; the different declaration only affects whether you can call it with a constargument, it doesn't affect the operations involved. Should this outcome be reconsidered?

Proposed resolution (April, 2016):

1. Change 11.4.5.3 [class.copy.ctor] paragraph 12 as follows:

A copy/move constructor for class X is trivial if it is not user-provided, its parameter-type-list is equivalent to the parameter-type-list of an implicit declaration, and if...

1. Change 11.4.5.3 [class.copy.ctor] paragraph 25 as follows:

A copy/move assignment operator for class X is trivial if it is not user-provided, its parameter-type-list is equivalent to the parameter-type-list of an implicit declaration, and if...