Re: RS6000 buried treasure - NO_IMPLICIT_EXTERN_C

[Stan Shebs <shebs at apple dot com>]

Dale Johannesen wrote:

> On Friday, November 8, 2002, at 11:20  AM, Zack Weinberg wrote:
>
> > On Fri, Nov 08, 2002 at 10:56:24AM -0500, David Edelsohn wrote:
> >
> > > > I am inclined to enable NO_IMPLICIT_EXTERN_C for the entire directory,
> > > > in rs6000.h.  What few targets this is inappropriate for -- I'm
> > > > willing to bet that's either none, or only AIX 3.1 -- can #undef it
> > > > again.
> > > >
> > > > Comments?
> > >
> > >     I could see placing this in sysv4.h, but not rs6000.h.  I do not
> > > believe that GCC's fixincludes completely addresses the C++ issues 
> > > in the
> > > AIX header files.  IBM Visual Age C++ distributes its own system header
> > > files.
> >
> > Defining or not defining NO_IMPLICIT_EXTERN_C addresses only one C++
> > issue with system headers.  It should be defined by all targets where
> > the system headers already wrap declarations in extern "C" { ... }
> > when appropriate, and not defined otherwise.  Is it really the case
> > that no AIX release provides extern "C" markers?
>
> Darwin headers seem to provide extern "C", at least in the examples I
> tried, although I'm not sure I understand what "when appropriate"
> is exactly.  However, darwin.h doesn't currently define 
> NO_IMPLICIT_EXTERN_C,
> and I'm not aware of any problems with the way things work now
> (it's possible the same altivec.h problem exists, though), so I'd
> request that somebody at least try it on Darwin before changing it.
Alas, many of the Mach headers are unprotected, even in 6.2, although
I believe that will be fixed in a future release.  So if it got defined in
rs6000.h, we'd have to undef in darwin.h.

Stan