[Bug libstdc++/113500] Using std::format with float or double based std::chrono::time_point causes error: no match for 'operator<<'

["redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113500

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #6)
> (In reply to Hirthammer from comment #5)
> > This whole thing with std::format and std::chrono::time_point is currently a
> > total minefield.
> 
> That seems like an exaggeration.
> 
> > In MSVC it is even more complicated and I already reported
> > the bug in October 2023. See:
> > 
> > https://developercommunity.visualstudio.com/t/Using-std::format-with-
> > unsigned-integer-/10501153
> > 
> > If you change the clock to utc_clock or gps_clock the code compiles with
> > MSVC (but not with GCC) on Compiler Explorer.
> 
> It compiles fine with GCC for me.

Ah, maybe you mean your original example. The one at in the MSVC bug report
compiles fine with GCC using utc_clock and gps_clock.

Your original example doesn't, because formatting a utc_time or gps_time is
specified in terms of a sys_time, and that's how libstdc++ implements it. So if
the utc_time or gps_time uses a float rep, we're back to square one.

I'll ask the committee to clarify that too.