The helper function
RetType compareThreeWay(const T &left, const T &right) noexcept;
is used for C++20-comparison macros. Normally it's the user's
responsibility to provide this function as a hidden friend of the class
which uses the comparison helper macros.
For built-in types we provide the implementation inside the Qt
namespace.
We have to use custom IsIntegralType trait because libstdc++ only
treats __{u}int128_t types as integral when compiling in -std=gnu++XX
mode, and we compile Qt in -std=c++XX mode.
This patch provides the implementations only for compareThreeWay()
overloads, because there is no need to implement comparesEqual() for
built-in types. It would just be equivalent to calling operator==(),
so the user can do it directly.
Task-number: QTBUG-104113
Change-Id: I7b3f395458e1ee4c64f442ad48bbf4fec4c19c52
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
96f494bf92