On Tue, Jan 21, 2014 at 9:42 AM, Richard Stallman <rms@gnu.org> wrote:

>     Fine, but what's the policy now regarding features that require an
>     installed clang to work; can they be merged to Emacs proper or not?
>
> Emacs (and all GNU packages involving C code) should be designed to
> work best with GCC.  There should be nothing to encourage users not to
> use our compiler.


Richard,

That really does not answer David's question.  If you read it carefully he
called out "features that require an installed clang to work".  That is the
crux of the tension here.  While the most obvious manifestation of clang is
as a C/C++ compiler very similar to gcc it is also much more.  That is
because it is architected as suite of libraries intended to be integrated
into more environments than just a compiler:

http://clang.llvm.org/features.html#libraryarch
http://clang.llvm.org/features.html#ideintegration

Tooling for analyzing and manipulating C/C++ is simply a space that gcc is
not addressing.  Based on its architecture it likely never will.

There exist now various packages integrating emacs will elements of clang.
 These packages are not supporting clang as alternative compiler.  Rather
by exploiting clang interfaces that have no gcc analog they offer exciting
IDE-like features.

/john