On Thu, 13 Mar 2025, Ville Voutilainen wrote: > On Thu, 13 Mar 2025 at 23:16, Ville Voutilainen > <ville.voutilai...@gmail.com> wrote: > > > > On Thu, 13 Mar 2025 at 23:03, Patrick Palka <ppa...@redhat.com> wrote: > > > + // Defined as a template to work around PR libstdc++/116440. > > > + template<class...> > > > + constexpr explicit(!__convertible<const _Elements&...>()) > > > + tuple(const _Elements&... __elements) > > > > I don't understand how a constructor template declared like this can > > ever be called. The template parameter pack > > can't be provided or deduced, and can't have a default. So we're > > effectively making this signature always lose > > overload resolution to the one that takes a pack of _UElements&&. > > > > Which may be fine. I can't head-compile a test that would fail in that > > case. If any of the incoming argument isn't one > > of _Elements, that constructor wins overload resolution anyway. If the > > incoming arguments are exactly _Elements, that > > constructor does the same thing as this one. I think. > > Oh, never mind. The pack is just deduced as an empty pack.
Yep that's my understanding, though I don't know where in the standard this is specified, a quick Ctrl+F is failing me. I can use template<int = 0> or template<typename = void> if that's preferred :)
