This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 108i. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2022-07-16


2171. Triviality of copy constructor with less-qualified parameter

Section: 11.4.5.3  [class.copy.ctor]     Status: CD4     Submitter: Jason Merrill     Date: 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 const argument, 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:

  2. 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...
  3. Change 11.4.5.3 [class.copy.ctor] paragraph 25 as follows:

  4. 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...