Some shadow fixes.

[Nathan Myers]

On Thu, May 18, 2000 at 12:36:21PM -0700, Steven King wrote:
> This patch fixes some typos that prevent compilation and adds some 
> required symbols. Additionally, I've restructured the way cmath 
> exposes the double precision routines, using a inline forwarding 
> function instead of a using directive makes for better looking 
> error messages.  I'm somewhat of the opinion that all of the 
> shadowed functions should be done this way.
> 
> 2000-05-18 Steven King <sxking@uswest.net>
> 
>  	* shadow/math.h: Add ::abs(float), ::abs(double) as inline
> 	forwardingcall to std::abs(float), std::abs(double);
> ...
> >   //we cant use using ::std::abs; here
> >   inline float abs (float __x) { return std::abs (__x); }
> >   inline double abs (double __x) { return std::abs (__x); }

Unfortunately, the standard requires that the ::abs visible when you 
include <math.h> be identically the same function as the std::abs.  
it also defines.  The same applies if somebody includes <cmath> 
and you later include <math.h>, or vice versa.

In practice, this means you have to hide the extern "C" declaration 
in a namespace somewhere, and define a single inline forwarding 
function to expose in various namespaces.  There are several examples 
of this in the shadow headers already; it seems we must use the same 
trick for the math functions too.  

Note, though, that the C++ standard doesn't include the C99 extensions,
so any such have to be guarded with #ifdef __USE_C9X.

Nathan Myers
ncm at cantrip dot org