CWG Issue 263 (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

263. Can a constructor be declared a friend?

Section: 11.4.5 [class.ctor]Status: CD1Submitter: Martin SeborDate: 13 Nov 2000

[Voted into WP at April 2003 meeting.]

According to 11.4.5 [class.ctor] paragraph 1, a declaration of a constructor has a special limited syntax, in which only _function-specifier_s are allowed. A friendspecifier is not a function-specifier, so one interpretation is that a constructor cannot be declared in a frienddeclaration.

(It should also be noted, however, that neither friendnor function-specifier is part of the declaratorsyntax, so it's not clear that anything conclusive can be derived from the wording of 11.4.5 [class.ctor].)

Notes from 04/01 meeting:

The consensus of the core language working group was that it should be permitted to declare constructors as friends.

Proposed Resolution (revised October 2002):

Change paragraph 1a in 6.5.5.2 [class.qual] (added by the resolution of issue 147) as follows:

If the nested-name-specifier nominates a class C, and the name specified after the nested-name-specifier, when looked up inC, is the injected-class-name of C ( Clause 11 [class]), the name is instead considered to name the constructor of class C. Such a constructor name shall be used only in the declarator-id of a constructor definition declaration that appears outside of the class definition names a constructor....

Note: the above does not allow qualified names to be used for in-class declarations; see 9.3.4 [dcl.meaning] paragraph 1. Also note that issue 318 updates the same paragraph.

Change the example in 11.8.4 [class.friend], paragraph 4 as follows:

class Y { friend char* X::foo(int); friend X::X(char); // constructors can be friends friend X::~X(); // destructors can be friends //... };