CWG Issue 3007 (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

3007. Access checking during synthesis of defaulted comparison operator, take 2

Section: 11.10.1 [class.compare.default]Status: openSubmitter: Jason MerrillDate: 2025-03-13Liaison: EWG

Issue 2568 sought to make the following situation well-formed:

struct Base { protected: bool operator==(const Base& other) const = default; };

struct Child : Base { int i; bool operator==(const Child& other) const = default; };

bool b = Child() == Child(); // error: deleted operator==

However, the applied resolution of that issue failed to achieve the intent, because the object expression has type Base when invoking Base::operator== in the synthesized body of Child::operator==, per 11.10.1 [class.compare.default] paragraph 5 together with 11.10.2 [class.eq] paragraph 2 and 11.10.3 [class.spaceship] paragraph 2. The synthesized body of Child::operator== looks like this:

bool Child::operator==(const Child& other) const { return (static_cast<const Base&>(*this) == static_cast<const Base&>(other)); // error, protected }

Additional notes (March, 2025)

EWG should decide whether the design intent is to allow access to Base::operator== in the example. Forwarded to EWG withpaper issue #2239by decision of the CWG chair.