[Bug c++/21092] New: friend inaccessibility

[Bug c++/21092] New: friend inaccessibility

[Ralf dot Wildenhues at gmx dot de]

A recent change on CVS HEAD breaks this:
$ cat a.cc
class X {
  friend class Y;
  friend int foo(const Y&);
};
$ g++ -c -W -Wall a.cc
a.cc:3: error: expected ',' or '...' before '&' token
a.cc:3: error: ISO C++ forbids declaration of 'Y' with no type

The original bug report is against CLN with possibly more info
of value, and may be read here:
http://thep.physik.uni-mainz.de/pipermail/cln-list/2005-April/000119.html

AFAIK gcc-4.0.0 is fine.

-- 
           Summary: friend inaccessibility
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: Ralf dot Wildenhues at gmx dot de
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21092

[Bug c++/21092] friend inaccessibility

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-04-18 19:40 -------
No, the code is invalid, as Y has not been interjected yet.  This is a progression and not a regression.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21092

[Bug c++/21092] friend inaccessibility

[kreckel at ginac dot de]

------- Additional Comments From kreckel at ginac dot de  2005-04-18 20:19 -------
(In reply to comment #1)
> No, the code is invalid, as Y has not been interjected yet.  This is a
progression and not a regression.

Really?  What about paragraph 11.4/7 "A name nominated by a friend
declaration shall be accessible in the scope of the class containing the
friend declaration."


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21092

[Bug c++/21092] friend inaccessibility

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2005-04-18 20:29 -------
This sentence just says that you can't do this: 
  class A { private: struct I{}; }; 
  class B { friend class A::I;   }; 
because A::I isn't accessible in B. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21092

[Bug c++/21092] friend inaccessibility

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2005-04-18 20:34 -------
And the answer to the original question: even though gcc handled it as this 
in the past (incorrectly), a friend declaration is not a declaration. In 
other words, if a name is not declared before, but first seen in a friend 
declaration, then this does not make this name known. This is the problem 
you run against: class Y is only marked for friendship in the friend 
declaration, 
for when the class is actually declared later on. However, it is still 
undeclared once you get to the function declaration. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21092

[Bug c++/21092] friend inaccessibility

[kreckel at ginac dot de]

------- Additional Comments From kreckel at ginac dot de  2005-04-18 21:04 -------
(In reply to comment #3)
> This sentence just says that you can't do this: 
>   class A { private: struct I{}; }; 
>   class B { friend class A::I;   }; 
> because A::I isn't accessible in B. 

Where's that snippet from?  As it stands, it's out of any context whatsoever.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21092

[Bug c++/21092] friend inaccessibility

[kreckel at ginac dot de]

------- Additional Comments From kreckel at ginac dot de  2005-04-18 21:08 -------
(In reply to comment #5)
> (In reply to comment #3)
> > This sentence just says that you can't do this: 
> >   class A { private: struct I{}; }; 
> >   class B { friend class A::I;   }; 
> > because A::I isn't accessible in B. 
> 
> Where's that snippet from?  As it stands, it's out of any context whatsoever.

Oh, sorry.  Now I understand what you're referring to.

11.4/9 appears to be the relevant section in this case.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21092