Comment out unused parameters

[e-kwsm]

No description provided.

[ghutchis]

Sorry, I'm not going to merge anything C++17 anytime soon. C++11 is okay, though. We need to be intentionally very conservative with support.

[e-kwsm]

The attribute is not effective unless -std=c++17 is supplied. Actually there are many unused variables.

[correaa]

Sorry, I'm not going to merge anything C++17 anytime soon. C++11 is okay, though. We need to be intentionally very conservative with support.

Good call.

I think the fallback case should be to use nothing. (evaluate UNUSED(x) to `` --nothing--). #2376

Besides [[maybe_unused]] is only for C++17, the keyword is not for that™.
[[maybe_unused]] is mainly for generic code or macros, if constexpr, etc.

An unused variable shouldn't be named in the first place.
At most have a commented name f(double /*unused x*/) (Linters recommend that).
There is nothing wrong with not naming the unusued variable, there is no need to make acrobatics with unused attributes.

[e-kwsm]

The original motivation is to replace UNUSED macro with [[maybe_unused]] attribute, so this does not fix all of the warning on unused parameters.

[e-kwsm]

Now the unused parameters are commented out as far as clang-tidy does.