[PATCH] D55150: Emit warnings from the driver for use of -mllvm or -Xclang options.

Thu Dec 6 11:57:04 PST 2018

kristina requested changes to this revision.
kristina added a comment.

In D55150#1321829 <https://reviews.llvm.org/D55150#1321829>, @efriedma wrote:

> I'm not sure that putting a warning that can be disabled really helps here; anyone who needs the option will just disable the warning anyway, and then users adding additional options somewhere else in the build system will miss the warning.
>
> Instead, it would probably be better to rename Xclang and mllvm to something that makes it clear the user is doing something unsupported. Maybe "--unstable-llvm-option" and "--unstable-clang-option" or something like that.  (This will lead to some breakage, but the breakage is roughly equivalent for anyone using -Werror.)

Thinking about it more, downstream forks with custom passes may utilize those flags in tests, renaming them is definitely not the way to go, that is going to cause a lot of problem and possibly a lot of angry downstream users as well as contributors. Some out-of-tree test suites will treat warnings as failures so that behavior by default is also a possible cause for concern. I *really* think just changing the documentation to inform consumers about what the flags are intended for. In fact `-mllvm` is used extensively in a lot of lit/FileCheck tests, so that's also going to cause problems.

I think it's best to just document these options better, I agree, the documentation is extremely poor but anything beyond that will/could cause issues in so many places.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55150/new/

https://reviews.llvm.org/D55150