Re: c++/10437: "using namespace" at global scope creates incorrect code

[Wolfgang Bangerth <bangerth@ices.utexas.edu>]

The following reply was made to PR c++/10437; it has been noted by GNATS.

From: Wolfgang Bangerth <bangerth@ices.utexas.edu>
To: Dean Foster <foster@diskworld.wharton.upenn.edu>
Cc: dean@foster.net, <gcc-bugs@gcc.gnu.org>, <gcc-gnats@gcc.gnu.org>
Subject: Re: c++/10437: "using namespace" at global scope creates incorrect
 code
Date: Mon, 21 Apr 2003 15:03:33 -0500 (CDT)

 > I'm willing to agree that that I've have an error/ambiguity in my
 > code.  But I don't understand why bringing in a namespace that isn't
 > being called should change the ambiguity status.
 
 The point is that in order to find out which function the compiler 
 shall take, it needs to know about the possibilities. For this, the
 possible declarations must "work". Without knowing your choices, you can't 
 perform overload resolution.
 
 
 > In other words,
 > 
 > 		main()
 > 		{
 > 		  using namespace foo;
 > 		  /* ... */           // no error
 > 		}
 > doesn't generate an error. But, the following does generate an error:
 > 		  
 > 		using namespace foo;
 > 		main()
 > 		{
 > 		  /* ... */         // generates error
 > 		}
 > 
 > It seems that [they] should be the same. 
 
 I guess that should be so.
 
 I can't reproduce this with the small example I posted. Can you try to 
 come up with something short that shows this? Your original example was 
 incredibly contrived, and I don't want to go through the ordeal again of 
 reducing it, which took me well over an hour. Hint: try stripping template 
 parameters, and replacing typedefs by the types the point to, etc. Once 
 it's well below 100 lines I'll be willing to look at it again :-)
 
 W.
 
 -------------------------------------------------------------------------
 Wolfgang Bangerth              email:            bangerth@ices.utexas.edu
                                www: http://www.ices.utexas.edu/~bangerth/