[Bug c++/13495] New: Impossible "friend"-ship to nested template

[Bug c++/13495] New: Impossible "friend"-ship to nested template

[sstrasser at systemhaus-gruppe dot de]

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Hi.
I don´t exactly know what the correct syntax to do this is, since I couldn´t
look up in the specification, but it looks like a bug because
a) I couldn´t figure out a way to do this with GCC
b) I could figure out a way which does work with MSVC but doesn´t with GCC

so here it is:

a template class which contains a nested class which itself is no template but
inherits the template parameter:

template<typename T>
class A{
public:
  class B{};
};

class A<T>::B should be friend of another class:

template<typename T>
class OtherClass{
  XXX
};

A<T>::B is a dependent type, so using it requires the 'typename'-keyword.
("implicit typename deprecated")

a) XXX == friend typename A<T>::B; doesn´t work because it requires the
'class'-keyword because it´s a class friendship

b) XXX == friend class A<T>::B; doesn´t work because A<T>::B is a dependent
typename, which requires the 'typename' keyword.

c) XXX == friend typename class A<T>::B; or 
d) XXX == friend class typename A<T>::B pass out with parse error.

MSVC compiles a) (wrongly) and c) (possibly correct)

Thank you,

Stefan

-- 
           Summary: Impossible "friend"-ship to nested template
           Product: gcc
           Version: 3.3
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sstrasser at systemhaus-gruppe dot de
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495

[Bug c++/13495] Friendship to class nested withint a template is broken

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2003-12-27 09:03 -------
It's been clarified by DR180 that the form:

friend class A<T>::B;

is the only allowed. In fact, the name is implicitily a type because of 
the 'class' keyword put in front of it, so a typename is not needed (and it is 
not allowed by syntax either). This has been correctly implemented by the new 
parser in GCC 3.4.

Then you must understand the difference between:

template<class T> class OtherClass {
   friend class A<T>::B;
};

and:

template<class T> class OtherClass {
   template <class Q>
   friend class A<Q>::B;
};

In the first case, you're saying that, for each OtherClass<X>, A<X>::B is a 
friend (only for the same X!). In the second, you're saying that for each 
OtherClass<X>, any A<Y>::B is a friend (for any Y).

Nonetheless, there is indeed a bug in GCC. I propose this testcase:

--------------------------------------------
template<typename T>
class A{
public:
    class B
    {
        void func1(void);
        void func2(void);
    };
};

template<typename Q>
class F1
{
    friend class A<Q>::B;
    enum { foo = 0 };
};

template<typename Q>
class F2
{
    template<typename T>
    friend class A<T>::B;
    enum { foo = 0 };
};

template <typename T>
void A<T>::B::func1(void)
{
    (void)F1<T>::foo;        // OK, A<T>::B is a friend for this T (#1)
    (void)F2<T>::foo;        // OK, any A<K>::B is a friend (#2)
}

template <typename T>
void A<T>::B::func2(void)
{
    (void)F1<double>::foo;   // ERROR, A<double>::T is not a friend (#3)
    (void)F2<double>::foo;   // OK, any A<K>::B is a friend (#4)
}

template class A<void>;
--------------------------------------------

Thus, GCC should emit an error only for #3. Instead it emits an error for #2 
and not for #3. This is clearly a bug (but not a regression, since the previous 
versions of GCC were even more broken wrt friendships to nested classes or 
specializations of templates).

This is a job for Kriang :)


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |accepts-invalid, rejects-
                   |                            |valid
   Last reconfirmed|0000-00-00 00:00:00         |2003-12-27 09:03:43
               date|                            |
            Summary|Impossible "friend"-ship to |Friendship to class nested
                   |nested template             |withint a template is broken
            Version|3.3                         |3.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495

[Bug c++/13495] Friendship to class nested withint a template is broken

[lerdsuwa at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |lerdsuwa at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495

[Bug c++/13495] Friendship to class nested withint a template is broken

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-08-30 15:33 -------
Kriang, it looks like g++.old-deja/g++.pt/friend44.C is related to this bug. 
The testcase is xfailed on mainline, and you already fixed half of it with your 
patch for PR5369. I guess your patch for this bug also cures that testcase?

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495

[Bug c++/13495] Friendship to class nested withint a template is broken

[lerdsuwa at gcc dot gnu dot org]

------- Additional Comments From lerdsuwa at gcc dot gnu dot org  2004-08-31 10:56 -------
Yes, the patch will also fix the warning produced
when testing g++.old-deja/g++.pt/friend44.C.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495

[Bug c++/13495] Friendship to class nested withint a template is broken

[lerdsuwa at gcc dot gnu dot org]

------- Additional Comments From lerdsuwa at gcc dot gnu dot org  2004-09-04 15:59 -------
Patch in progress.  Note that even with the fix,
GCC still doesn't diagnose the code in Comment #1
correctly because of PR16617.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495

[Bug c++/13495] Friendship to class nested withint a template is broken

[lerdsuwa at gcc dot gnu dot org]

------- Additional Comments From lerdsuwa at gcc dot gnu dot org  2004-09-06 15:55 -------
Patch submitted:
  http://gcc.gnu.org/ml/gcc-patches/2004-09/msg00557.html

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495

[Bug c++/13495] Friendship to class nested within a template is broken

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-10-20 16:20 -------
Subject: Bug 13495

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	lerdsuwa@gcc.gnu.org	2004-10-20 16:20:51

Modified files:
	gcc/cp         : ChangeLog cp-tree.h decl.c friend.c parser.c 
	                 pt.c 
	gcc/testsuite  : ChangeLog 
	gcc/testsuite/g++.old-deja/g++.pt: friend44.C 
Added files:
	gcc/testsuite/g++.dg/template: memfriend9.C memfriend10.C 
	                               memfriend11.C memfriend12.C 
	                               memfriend13.C memfriend14.C 
	                               memfriend15.C memfriend16.C 
	                               memfriend17.C 

Log message:
	PR c++/13495
	* decl.c (make_unbound_class_template): Add PARM_LIST parameter.
	* cp-tree.h (make_unbound_class_template): Adjust prototype.
	* parser.c (cp_parser_lookup_name): Adjust call to
	make_unbound_class_template.
	(cp_parser_single_declaration): Handle member class of class
	template as template friend parsing correctly.
	* friend.c (is_friend): Call is_specialization_of_friend for
	template friend class.
	(make_friend_class): Handle member class of class template as
	template friend.
	* pt.c (is_specialization_of_friend): Likewise.
	(instantiate_class_template): Likewise.
	(tsubst): Adjust call to make_unbound_class_template.
	
	* g++.dg/template/memfriend9.C: New test.
	* g++.dg/template/memfriend10.C: Likewise.
	* g++.dg/template/memfriend11.C: Likewise.
	* g++.dg/template/memfriend12.C: Likewise.
	* g++.dg/template/memfriend13.C: Likewise.
	* g++.dg/template/memfriend14.C: Likewise.
	* g++.dg/template/memfriend15.C: Likewise.
	* g++.dg/template/memfriend16.C: Likewise.
	* g++.dg/template/memfriend17.C: Likewise.
	* g++.old-deja/g++.pt/friend44.C: Remove bogus error.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.4447&r2=1.4448
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/cp-tree.h.diff?cvsroot=gcc&r1=1.1065&r2=1.1066
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/decl.c.diff?cvsroot=gcc&r1=1.1316&r2=1.1317
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/friend.c.diff?cvsroot=gcc&r1=1.101&r2=1.102
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/parser.c.diff?cvsroot=gcc&r1=1.267&r2=1.268
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/pt.c.diff?cvsroot=gcc&r1=1.936&r2=1.937
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.4478&r2=1.4479
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend9.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend10.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend11.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend12.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend13.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend14.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend15.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend16.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/memfriend17.C.diff?cvsroot=gcc&r1=NONE&r2=1.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.old-deja/g++.pt/friend44.C.diff?cvsroot=gcc&r1=1.3&r2=1.4



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495

[Bug c++/13495] Friendship to class nested within a template is broken

[lerdsuwa at gcc dot gnu dot org]

------- Additional Comments From lerdsuwa at gcc dot gnu dot org  2004-10-20 16:25 -------
I am closing this as fixed by patch:
  http://gcc.gnu.org/ml/gcc-patches/2004-10/msg01709.html

For access checking problem mentioned in the comments, it's 
already covered in PR16617.  That part requires some structural 
changes that won't be investigated for some time.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13495