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Bug 142423 - Incorrect scope for for inline class friend functions
Incorrect scope for for inline class friend functions
Product: Red Hat Enterprise Linux 3
Classification: Red Hat
Component: gcc3 (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Jakub Jelinek
Depends On:
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Reported: 2004-12-09 12:44 EST by Fedor Pikus
Modified: 2007-11-30 17:07 EST (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2004-12-29 07:56:20 EST
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RHEL 7.3 requirements from Atomic Host:
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Description Fedor Pikus 2004-12-09 12:44:04 EST
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.7.3)

Description of problem:
The following program should not compile:
class A
    A( int x0 = 0 ) : x( x0 ) {}
    friend int foo( const A& a ) { return a.x; }
    int x;
int main() 
    A a;
    int i = foo( 0 );

the call to foo() should require argument-dependent lookup but since
the argument is "int" not "A&", ADL cannot be performed. 

This can lead to rather bizarre behaviour, for example:
#include <iostream>
using namespace std;

template <typename T> class A
    A( T x0 = 0 ) : x( x0 ) {}
    friend T foo( const A& a ) { cout << "A::foo" << endl; return a.x; }
    T x;

template <typename T> class B
    B( T x0 = 0 ) : x( x0 ) {}
    friend T foo( const B& a ) { cout << "B::foo" << endl; return a.x; }
    T x;

int main()
        A<int> a = 0;
        int i = foo( a ); 
        int j = foo( 0 ); 
        B<int> b = 0;
        int i = foo( b ); 
        int j = foo( 0 ); 

In this program the error message is:
lookup4.C: In function `int main()':
lookup4.C:30: call of overloaded `foo(int)' is ambiguous
lookup4.C:8: candidates are: int foo(const A<int>&)
lookup4.C:16:                 int foo(const B<int>&)

Call on line 30 is ambiguous but call on line 25 is not (and indeed
compiles if line 30 is commented out, A::foo is called). 

Version-Release number of selected component (if applicable):
gcc version 3.2.3 20030502 (Red Hat Linux 3.2.3-34)
Comment 2 Jason Merrill 2004-12-27 14:43:22 EST
g++ still injects the names of friend functions into the enclosing namespace;
this is obsolete behaviour which was removed from the language in favor of
argument-dependent lookup of friend functions, but g++ has not yet caught up.
Comment 3 Jakub Jelinek 2004-12-29 07:56:20 EST
Given that even current CVS HEAD doesn't handle this, I'm closing this as
UPSTREAM.  When/if upstream fixes this and if the fix is simple enough, we might
consider backporting it (but RHEL4 has certainly bigger chance of backporting
that than RHEL3).

Jason, is there any PR about this in gcc.gnu.org/bugzilla?

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