Work around false SLOTS defined but not used warning on GCC

[Pokechu22]

This warning was caused by #10364; see e.g. this build log. The bug in question is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80351, and it seems to be solvable by explicitly using std::initializer_list instead of auto. The warning is generated only for the first auto initializer list, but we need to change both SLOTS and MEMCARD_SLOTS as if only SLOTS is changed, then MEMCARD_SLOTS becomes the first auto initializer list and generates a warning. An alternative solution is to mark SLOTS as [[maybe_unused]], which does not require changing MEMCARD_SLOTS, but that seems a bit silly. (I've requested an account on the GCC bugzilla to add some additional notes there, but it hasn't been created yet.)

[shuffle2]

why not just explicitly state the type and make it a [] or std::array?

[Pokechu22]

I don't think there's much of a benefit of using [] or std::array over explicitly stating that it's a std::initializer_list, but using either [] or std::array would require also listing the length (but I don't think it'd have any difference in performance or anything). auto deduces to std::initializer_list here, so there isn't any behavior difference from this change.

[shuffle2]

[] doesn't require listing the length. the benefit is just that initializer_list is some new(er) jargon which apparently still has spotty support on some compilers. there should be no behavior difference in any case, but just using something like a plain old array seems simple and straightforward here (not that it really matters one way or the other, really - apart from the fact some workaround is needed).

[lioncash]

It's definitely more idiomatic to use std::array for this sort of thing over an initializer_list. It's also shorter since with template deduction guides, you wouldn't need to state the size, you would just do:

constexpr std::array SLOTS = {Slot::A, Slot::B, Slot::SP1};

[Pokechu22]

The freebsd builder doesn't like to deduce std::array, see https://dolphin.ci/#/builders/13/builds/5852

[lioncash]

I think that's indicative more than anything that the freebsd builder needs to be updated, given that deduction guides have been supported by std lib implementations for quite a while now

[Pokechu22]

For what it's worth, I've submitted a patch to GCC to fix this issue, and the patch is expected to land in GCC 13.

[Pokechu22]

The patch has been merged, though it will be a while before it ends up in a release build of GCC (GCC 12 just entered the release candidate state, and this patch is for the GCC 13 branch).