Apple clang 14.0.3 surfaces new default warnings; -Werror breaks Darwin builds

Is this due to a new toolchain?

According to @angerman, there wasn't a OS/toolchain update that would have made this start happening.

Update: The machines do have a newer version of clang than (some) other Darwin machines, so this is probably a factor.

Did something change recently in build configs that exposed these errors?

94f00e9b added -optc-Werror to the +werror transformer, but that happened back in December. I wouldn't expect to start seeing problems now.

Update: This was only merged last week, so it is definitely related.

Why are they coming piecemeal?

5b6612bc was written because "Darwin's toolchain inexplicably claims that write_barrier and friends have declarations without prototypes". But now there are more such functions. https://gitlab.haskell.org/ghc/ghc/-/jobs/1571118 complains of initAdjustors; https://gitlab.haskell.org/ghc/ghc/-/jobs/1571356 complains of reportMemoryMap; https://gitlab.haskell.org/ghc/ghc/-/jobs/1571120 complains that FFI_GO_CLOSURES is undefined (moved to #23568 (closed) since it's a different problem.) -Werror is complicit in all of these.

Update: This is probably due to the nondeterminism of a multi-core build.