[libc++] Add std::fpclassify overloads for floating-point.

[tolikmalibroda]

Standard says that implementation of math functions that have floating-point-type parameter should provide an "overload for each cv-unqualified floating-point type".

[philnik777]

The implementation looks good, but this needs tests. Specifically,

• there should be a regression test to make sure an implicit conversion works now
• please make sure that we have test coverage for the _LIBCPP_NODISCARD_EXTs
• please make sure that we have test for the noexceptness of the overloads.

You should be able to find tests for this under libcxx/test/libcxx/{diagnostics,numerics/c.math} if they exist.

[tolikmalibroda]

Sorry, I pulled commits from main :(
I'll revert it

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[tolikmalibroda]

Now code diff's showing correct changes. But I'll probably need to create new PR to merge changes without extra commits...

Added tests for implicit conversions and noexceptness to libcxx/test/std/numerics/c.math/cmath.pass.cpp.
Tests for nodiscard already exist in libcxx/test/libcxx/diagnostics/math_nodiscard_extensions.verify.cpp.

[philnik777]

You can just rebase to fix your issues.

[tolikmalibroda]

Maybe I've done something wrong, but I've rebased and those all commits from main were added ahead of mine and appeared here...
I can somehow fix that and remove these commits from PR?

[philnik777]

You probably did something wrong while rebasing. In a rebase workflow you want a single commit that you're force-pushing to your branch generally. It looks like you had a merge commit or something like that and the new commits got rebased onto that, resulting in different hashes; i.e. different commits. When running git log HEAD...main in your branch you should see only the commits you want to be part of this PR until you see origin/main, or upstream/main or whatever you named the upstream repo. (And no worries; I pinged dozens of people a few times too when I screwed up a rebase - happens to everyone)

[tolikmalibroda]

git log HEAD...main on my branch gives all commits that I've merged (when I did rebase) and then reverted + commits relevant to this PR. I don't know if I can remove them now...

[philnik777]

You should be able to git rebase -i main and then drop the commits.

[tolikmalibroda]

Many thanks, that worked! I should definitely read more documentation on how git rebase works and be more careful next time : )

[philnik777]

LGTM with a comment added.