[v3] Use Solaris prototypes if possible (PR libstdc++-v3/1773)

[Marc Glisse]

On Thu, 18 Aug 2011, Marc Glisse wrote:

> I think the current patch is good enough for now

Actually, could someone please append to this comment in tr1/cmath:

   // Note: we deal with fabs in a special way, because an using std::fabs
   // would bring in also the overloads for complex types, which in C++0x
   // mode have a different return type.

Something like:

   // With __CORRECT_ISO_CPP_MATH_H_PROTO1, math.h imports std::fabs in the
   // global namespace after the declarations of the float / double / long
   // double overloads but before the std::complex overloads.

so we remember why it works, why it breaks if users do silly things, and 
what needs changing if another platform tries to define 
__CORRECT_ISO_CPP_MATH_H_PROTO1.

> In the longer term, there is the usual idea that we could rename the current 
> cmath (just taking this one as an example) to math.h, make it #include_next 
> the system math.h (instead of plain #include), and have a trivial cmath that 
> just includes math.h. This way all the goodness in cmath would already be 
> available in math.h, conforming to D.5 (which one between math.h and cmath is 
> a trivial wrapper to the other is a technical detail that doesn't matter if 
> both are installed in the same directory).

... and I forgot that this requires adding many lines like:
using std::thing;
in the global namespace after the declarations in namespace std.

-- 
Marc Glisse