r224012 - Emit warning if define or undef reserved identifier or keyword.

[Joerg Sonnenberger]

On Thu, Dec 11, 2014 at 12:18:09PM -0000, Serge Pavlov wrote:
> Author: sepavloff
> Date: Thu Dec 11 06:18:08 2014
> New Revision: 224012
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=224012&view=rev
> Log:
> Emit warning if define or undef reserved identifier or keyword.

So I see valid applications for:

(1) #define const const, #define inline inline, etc --> autoconf has
been doing that a lot.
(2) #define restrict __restrict__ --> code that has to deal with pre-C99
default in GCC.
(3) #define extern, #define static --> debug, code sharing

In short, I wonder what kind of problems the default warning set is
supposed to find, which doesn't also have a decent list of valid users.

Joerg