On Sun, Dec 9, 2018 at 8:22 AM Darin Adler <darin@apple.com> wrote:
Best would be to eliminate “config.h”: Change “config.h” into an empty file first, then remove all “config.h” includes, and then remove the file. But to do that, we need to make sure every build system for WebKit supports prefix headers. I don’t know how close to that we are. Maybe close? How can we quickly find out?

 GCC and Clang support '-include <file>' option.

  https://gcc.gnu.org/onlinedocs/gcc/Preprocessor-Options.html
  https://clang.llvm.org/docs/ClangCommandLineReference.html

GTK and WPE ports are using it only in WK2 since r163032.

  https://trac.webkit.org/changeset/163032

MSVC has /FI option.

  /FI (Name Forced Include File) | Microsoft Docs
  https://docs.microsoft.com/en-us/cpp/build/reference/fi-name-forced-include-file?view=vs-2017

Unfortunately, it seems that MSVC's precompiled header needs to be included explicitly.

  /Yu (Use Precompiled Header File) | Microsoft Docs
  https://docs.microsoft.com/en-us/cpp/build/reference/yu-use-precompiled-header-file?view=vs-2017