[libc-commits] [libc] [libc] Support configurable errno modes (PR #98287)

[Roland McGrath via libc-commits]

https://github.com/frobtech approved this pull request.

LGTM now. I think we could refine a little how we make the overlay vs full mode setting interact with the option, but it's a little hairy to decide what we want and it doesn't seem crucial.  Likewise I think we should clarify and fully specify the plan about per-function/symbol headers and how that relates to errno/__llvm_libc_errno inside the tree. But that too is not urgent. When we do that we should start using `-Wprototypes` or whatever it is that complains if we define `__llvm_libc_errno` without a prior header declaration being in scope.

https://github.com/llvm/llvm-project/pull/98287