[Bug c++/35927] New: befriending a whole template in another namespace fails

[Bug c++/35927] New: befriending a whole template in another namespace fails

[mec at google dot com]

In this program, Beta::Gamma declares ::Alpha as a friend, but the friendship
does not work.

===

mec@hollerith:~/exp-friend$ cat z1.cc
template <typename T>
void Alpha(T* a) { a->Delta(); }

namespace Beta {

class Gamma {
 public:
  template <typename T> friend void ::Alpha(T*);

 private:
  void Delta();
};

}

int main() {
  Beta::Gamma* a = new Beta::Gamma;
  ::Alpha(a);
}

bash: /home/mec/gcc-4.2.1/install/bing++: No such file or directory
mec@hollerith:~/exp-friend$ /home/mec/gcc-4.2.1/install/bin/g++ -O2 -Wall -c
z1.cc
z1.cc: In function 'void Alpha(T*) [with T = Beta::Gamma]':
z1.cc:18:   instantiated from here
z1.cc:11: error: 'void Beta::Gamma::Delta()' is private
z1.cc:2: error: within this context

mec@hollerith:~/exp-friend$ /home/mec/gcc-4.2.2/install/bin/g++ -O2 -Wall -c
z1.cc
z1.cc: In function 'void Alpha(T*) [with T = Beta::Gamma]':
z1.cc:18:   instantiated from here
z1.cc:11: error: 'void Beta::Gamma::Delta()' is private
z1.cc:2: error: within this context

mec@hollerith:~/exp-friend$ /home/mec/gcc-4.3.0/install/bin/g++ -O2 -Wall -c
z1.cc
z1.cc: In function 'void Alpha(T*) [with T = Beta::Gamma]':
z1.cc:18:   instantiated from here
z1.cc:11: error: 'void Beta::Gamma::Delta()' is private
z1.cc:2: error: within this context
mec@hollerith:~/exp-friend$ 

===

In this program, Beta::Gamma declares the specialization ::Alpha<Beta::Gamma>
as a friend.  This works.

ec@hollerith:~/exp-friend$ cat z3.cc
template <typename T>
void Alpha(T* a) { a->Delta(); }

namespace Beta {

class Gamma {
 public:
  friend void ::Alpha<Beta::Gamma>(Beta::Gamma*);

 private:
  void Delta();
};

}

int main() {
  Beta::Gamma* a = new Beta::Gamma;
  ::Alpha(a);
}

mec@hollerith:~/exp-friend$ /home/mec/gcc-4.2.1/install/bin/g++ -O2 -Wall -c
z3.cc
mec@hollerith:~/exp-friend$ /home/mec/gcc-4.2.2/install/bin/g++ -O2 -Wall -c
z3.cc
mec@hollerith:~/exp-friend$ /home/mec/gcc-4.3.0/install/bin/g++ -O2 -Wall -c
z3.cc
mec@hollerith:~/exp-friend$

===

I think z1.cc is valid, per this clause from [temp.friend]:

"A template friend declaration specifies that all specializations of that
template, whether they are implicitly instantiated (14.7.1), partially
specialized (14.5.4) or explicitly specialized (14.7.3) are friends of the
class containing the template friend declaration.

I suspect it's a bug with the namespace part of "template <typename T> friend
void ::Alpha(T*);".


-- 
           Summary: befriending a whole template in another namespace fails
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mec at google dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35927

[Bug c++/35927] befriending a whole template in another namespace fails

[bangerth at dealii dot org]

------- Comment #1 from bangerth at dealii dot org  2008-04-14 14:21 -------
I too believe that z1.cc is valid. icc accepts it.

Not a regression, the code fails back to 2.95.
W.


-- 

bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at dealii dot org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2008-04-14 14:21:17
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35927

[Bug c++/35927] befriending a whole template in another namespace fails

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35927

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|gcc-bugs at gcc dot gnu.org |
      Known to work|                            |4.6.0, 4.6.1, 4.7.0
         Resolution|                            |FIXED

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-09-26 22:54:16 UTC ---
Fixed in 4.6.0.