These appear to be noexcept-able. Osama Abdelkader <[email protected]> 於 2025年10月18日 週六 下午10:50寫道：
> This fixes the C++23 compliance issue where std::tuple<> cannot be compared > with other empty tuple-like types such as std::array<T, 0>. > > The operators correctly allow comparison with array<T, 0> even when T is > not > comparable, because empty tuple-like types don't compare element values. > > libstdc++-v3/ChangeLog: > > PR libstdc++/119721 > * include/std/tuple: Add tuple<> comparison operators for > empty tuple-like types. > > Signed-off-by: Osama Abdelkader <[email protected]> > --- > v2: > - Replaced explicit array<T, 0> operators with generic tuple-like operators > - Only operator== and operator<=> are provided > - Operators work with any empty tuple-like type > - No need for reversed argument order > --- > libstdc++-v3/include/std/tuple | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/libstdc++-v3/include/std/tuple > b/libstdc++-v3/include/std/tuple > index 0ca616f1b..800f6e372 100644 > --- a/libstdc++-v3/include/std/tuple > +++ b/libstdc++-v3/include/std/tuple > @@ -2001,6 +2001,25 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > tuple(allocator_arg_t, const _Alloc&, const tuple&) noexcept { } > }; > > +#if __cpp_lib_tuple_like // >= C++23 > + // Comparison operators for tuple<> with other empty tuple-like types > + // Note: These operators allow comparison with any empty tuple-like > type, > + // including array<T, 0> and span<T, 0>, where T may not be comparable. > + // This is correct because empty tuple-like types don't compare > elements. > + template<__tuple_like _UTuple> > + requires (!__is_tuple_v<_UTuple> && tuple_size_v<_UTuple> == 0) > + [[nodiscard]] > + constexpr bool > + operator==(const tuple<>&, const _UTuple&) > + { return true; } > + > + template<__tuple_like _UTuple> > + requires (!__is_tuple_v<_UTuple> && tuple_size_v<_UTuple> == 0) > + constexpr strong_ordering > + operator<=>(const tuple<>&, const _UTuple&) > + { return strong_ordering::equal; } > +#endif // C++23 > + > #if !(__cpp_concepts && __cpp_consteval && __cpp_conditional_explicit) // > !C++20 > /// Partial specialization, 2-element tuple. > /// Includes construction and assignment from a pair. > -- > 2.43.0 > >
