On Tue, Mar 05, 2019 at 15:47:16 -0500, Mathias Stearn wrote:
> [1] Currently, with gcc and clang, you need to "partially preprocess" using
> -fdirectives-only or -frewrite-includes because those tools behave
> differently when compiling TUs that have already been fully preprocessed. I
> haven't tried doing a similar experiment with MSVC to know how well it
> handles fully preprocessed files.

There was discussion of this on Reddit a while ago:

    https://www.reddit.com/r/cpp/comments/6abi99/rfc_issues_with_separate_preprocess_and_compile/

--Ben