[C++ PATCH] Fix bug 75 (a regression)

[Nathan Sidwell <nathan at codesourcery dot com>]

Hi,
I've installed the attached on both the mainline and 3.0 branch, which
fixes bug 75, we we'd give an error when accessing a function already
in the current namespace via a using decl - that's not introducing the
function. It also now gives an error when the return type of extern "C"
functions so introduced _don't_ match.

built & tested on i686-pc-linux-gnu, approved by Mark.

nathan
-- 
Dr Nathan Sidwell   ::   http://www.codesourcery.com   ::   CodeSourcery LLC
         'But that's a lie.' - 'Yes it is. What's your point?'
nathan@codesourcery.com : http://www.cs.bris.ac.uk/~nathan/ : nathan@acm.org
2001-02-26  Nathan Sidwell  <nathan@codesourcery.com>

	* decl2.c (do_nonmember_using_decl): Don't complain if we find
	same function. Do complain about ambiguating extern "C"
	declarations.

Index: cp/decl2.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/cp/decl2.c,v
retrieving revision 1.443
diff -c -3 -p -r1.443 decl2.c
*** decl2.c	2001/02/19 21:47:08	1.443
--- decl2.c	2001/02/26 15:50:44
*************** do_nonmember_using_decl (scope, name, ol
*** 5126,5147 ****
  	    {
  	      tree old_fn = OVL_CURRENT (tmp1);
  
! 	      if (!OVL_USED (tmp1)
! 		  && compparms (TYPE_ARG_TYPES (TREE_TYPE (new_fn)),
! 				TYPE_ARG_TYPES (TREE_TYPE (old_fn))))
  		{
! 		  if (!(DECL_EXTERN_C_P (new_fn)
! 			&& DECL_EXTERN_C_P (old_fn)))
! 		    /* There was already a non-using declaration in
! 		       this scope with the same parameter types.  */
! 		    cp_error ("`%D' is already declared in this scope",
! 			      name);
  		  break;
  		}
- 	      else if (duplicate_decls (new_fn, old_fn))
- 		/* We're re-using something we already used 
- 		   before.  We don't need to add it again.  */ 
- 		break;
  	    }
  
  	  /* If we broke out of the loop, there's no reason to add
--- 5126,5146 ----
  	    {
  	      tree old_fn = OVL_CURRENT (tmp1);
  
!               if (new_fn == old_fn)
!                 /* The function already exists in the current namespace.  */
!                 break;
! 	      else if (OVL_USED (tmp1))
! 	        continue; /* this is a using decl */
! 	      else if (compparms (TYPE_ARG_TYPES (TREE_TYPE (new_fn)),
! 		  		  TYPE_ARG_TYPES (TREE_TYPE (old_fn))))
  		{
! 	          /* There was already a non-using declaration in
! 		     this scope with the same parameter types. If both
! 	             are the same extern "C" functions, that's ok.  */
!                   if (!decls_match (new_fn, old_fn))
!     	            cp_error ("`%D' is already declared in this scope", name);
  		  break;
  		}
  	    }
  
  	  /* If we broke out of the loop, there's no reason to add
// Build don't link:
// 
// Copyright (C) 2001 Free Software Foundation, Inc.
// Contributed by Nathan Sidwell 26 Feb 2001 <nathan@codesourcery.com>

// Bug 75. using declarations cannot introduce functions which ambiguate
// those in the current namespace, BUT here we're reaccessing the current
// namespace -- the function is not being 'introduced'.

extern int a();
struct x {};

using ::x;
using ::a;

extern "C" void foo ();

namespace {
  extern "C" int foo ();
  using ::foo; // ERROR - already in use
}