Implement std::size and std::ssize for C-style arrays

[davidtranhq]

C++17 and C++20 defines template functions for deducing the size of C-style arrays. I've found this useful and the implementation is simple (pretty much identical to the implementation on cppreference).

[64]

LGTM, anyone else have objections to merging this? Alternatively it could live in cxxshim?

[Dennisbonke]

Two style nitpicks, other than that this looks good to me.

[no92]

I'd prefer the second commit to be squashed into the first, other than that LGTM.

[ArsenArsen]

Don't hijack std:: in frigg

[64]

Don't hijack std:: in frigg

i.e this could be changed to use the frg namespace or you could send a PR to cxxshim and put it there instead.

[davidtranhq]

Don't hijack std:: in frigg

yeah, not sure what's preferred here. I wanted it to match the corresponding get functions that were also overloaded in the std namespace + thought it fit better in frigg since the standard library defines these functions in <array>. Up to the maintainers where they want it to go.

[ArsenArsen]

<array> is included in freestanding in GCC 13. Either use GCC 13 snapshots (and more testing is always nice :) or a hack (though, you'd need to add it to this hack in particular).

Either way, frigg should not clash with the standard, and more conservatively, the standard namespace.

I recommend the GCC 13 route if you can afford using a compiler with potential regressions (and, again, finding and reporting such regressions is invaluable).

[ArsenArsen]

oh, also, FTR: adding stuff to std:: is explicitly UB, unless it's to specialize existing templates like is the case for std::get and std::tuple_{size,element}, which is why frigg works in hosted environments without this overload added.