[PATCH] D13828: Do not process __config file in C mode

[Richard Smith via llvm-commits]

rsmith added a comment.

In http://reviews.llvm.org/D13828#269391, @EricWF wrote:

> if `__config` is first included within an `extern "C"` it will define the header guard macro but nothing else


That's not how this macro works: the `__cplusplus` macro is not affected by `extern "C"`; it will be defined for all C++ compilations, whether or not we're in an `extern "C"` context. Personally, I'm sympathetic to coping with libc++'s headers being present in C compilations; it may be hard to avoid this in some circumstances, with some build tools.

If we want the `_LIBCPP_HAS_NO_SYSTEM_HEADER_PRAGMA` macro (and friends) defined by `<__config>` even in C, we could put `#ifdef __cplusplus` around just the specific parts of this header that don't work in C (the namespaces, `static_assert` emulation, `char16_t`/`char32_t`, and the use of `extern "C"`).


http://reviews.llvm.org/D13828