This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 116a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-12-19

2703. Three-way comparison requiring strong ordering for floating-point types, take 2

The resolution accepted for issue 2539 does not actually address the example in the issue, because overload resolution is never performed for expressions involved only built-in types.

Suggested resolution:

Change in 11.10.3 [class.spaceship] paragraph 1 as follows:

The synthesized three-way comparison of type R (17.11.2 [cmp.categories]) of glvalues a and b of the same type is defined as follows:

• If a <=> b is usable (11.10.1 [class.compare.default]) and can be explicitly converted to R using static_cast, static_cast<R>(a <=> b).
• Otherwise, if a <=> b is usable or overload resolution for a <=> b is performed and finds at least one viable candidate, the synthesized three-way comparison is not defined.
• Otherwise, ...