Builtins in `std'

[Mark Mitchell]

At startup, we push lots of builtins into `std'.  For example, we do:

  namespace std {
    extern "C" double fabs (double);
  };

This seems like a bad idea to me.  For one thing, we accept the
following entirely bogus program:

  void f() { std::fabs (3.0); }

This isn't C, where `void f() { fabs (3.0); }' is a legal program.

The compiler then has to go through tons of shenanigans if someone
tries to do something like:

  namespace std {
    int fabs;
  };

or even:

  namespace std {
    double fabs (double); // Should no longer have `C' linkage.
  };

Arguably, the former case should not be allowed, but the latter
probably should be.  (Does V3 give `fabs' C or C++ linkage?  The
standard says it's unspecified.)

There's no compatibility issue here, becuase we already broke:

  void f() { fabs (3.0); }

by putting the builtins in the `std' namespace.  Anyone writing a
standard library should be using `__builtin_fabs' anyhow for tidiness,
and I know that V3 does this.

So, any objections to just not doing the insertion into `std'?

--
Mark Mitchell                   mark@codesourcery.com
CodeSourcery, LLC               http://www.codesourcery.com