c++/7049: Overloading "cout <<" in one namespace obscures similar functions in a different namespace

c++/7049: Overloading "cout <<" in one namespace obscures similar functions in a different namespace

[steev]

>Number:         7049
>Category:       c++
>Synopsis:       Overloading "cout <<" in one namespace obscures similar functions in a different namespace
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jun 17 01:46:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Steev Wilcox
>Release:        3.1 (sparc-sun-solaris2.8)
>Organization:
>Environment:
Solaris 8
>Description:
If you define a operator<<(ostream&,thing) for an object X in one namespace, then in another namespace, define the same sort of function for a different object Y, it hides the original function so you can't print objects of type X in the namespace associated with object Y.

Fairly obvious workaround:  don't define operator<<'s in namespaces - make sure they always go in the global namespace.  Bjarne wouldn't be pleased, though.  I'm not 100% certain this is a bug and not a "feature" of C++ - it just looks suspicious.

I haven't been able to find this in the list of known bugs, but it doesn't mean it's not there.

Thanks for your time, Steev
>How-To-Repeat:
Compile bug2.cpp with "g++ -c bug2.cpp".  It'll fail in the way indicated in file "testout".  If you place the definition of the operator<< on Y in the global namespace, g++ can suddenly find the definition of operator<< on X.
>Fix:
For workaround, see above.
>Release-Note:
>Audit-Trail:
>Unformatted:

Re: c++/7049: Overloading "cout <<" in one namespace obscures similar functions in a different namespace

[paolo]

Synopsis: Overloading "cout <<" in one namespace obscures similar functions in a different namespace

Responsible-Changed-From-To: unassigned->paolo
Responsible-Changed-By: paolo
Responsible-Changed-When: Tue Jun 18 05:23:37 2002
Responsible-Changed-Why:
    .
State-Changed-From-To: open->closed
State-Changed-By: paolo
State-Changed-When: Tue Jun 18 05:23:37 2002
State-Changed-Why:
    Philip is right (also double checked with two other respected
    compilers).

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7049

Re: c++/7049 Overloading "cout <<" in one namespace obscures similar functions in a different namespace

[Philip Martin]

The following reply was made to PR c++/7049; it has been noted by GNATS.

From: Philip Martin <philip@codematters.co.uk>
To: steev@paradigmds.com, gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org, gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org
Cc:  
Subject: Re: c++/7049 Overloading "cout <<" in one namespace obscures similar functions in a different namespace
Date: 18 Jun 2002 12:30:14 +0100

 This is not a bug, that's how name lookup works.
 
 The compiler will lookup operator<< in the anonymous namespace where
 the statement "cout << x" occurs, the std:: namespace where ostream is
 defined, and the ns:: namespace where class X is defined.  Since the
 compiler will find an operator<< by doing this it won't look anywhere
 else.  In particular operator<< in the global namespace will not be
 considered.
 
 Put operator<< for X where it belongs, in the ns:: namespace that
 defines class X.
 
 -- 
 Philip

Re: c++/7049: Overloading "cout <<" in one namespace obscures similar functions in a different namespace

[paolo]

Synopsis: Overloading "cout <<" in one namespace obscures similar functions in a different namespace

State-Changed-From-To: feedback->open
State-Changed-By: paolo
State-Changed-When: Mon Jun 17 05:07:47 2002
State-Changed-Why:
    Attachments provided.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7049

Re: c++/7049: Overloading "cout <<" in one namespace obscures similar functions in a different namespace

[paolo]

Synopsis: Overloading "cout <<" in one namespace obscures similar functions in a different namespace

State-Changed-From-To: open->feedback
State-Changed-By: paolo
State-Changed-When: Mon Jun 17 02:13:16 2002
State-Changed-Why:
    Hi. For some reason, both 'bug2.cpp' and 'testout' got lost.
    Could you possibly provide them again?
    Thanks, Paolo.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7049