[Bug c++/52126] New: compilation error

[Bug c++/52126] New: compilation error

[tmmikolajczyk at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

             Bug #: 52126
           Summary: compilation error
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: tmmikolajczyk@gmail.com


I encountered a compilation error when compiling the following code:

template<typename T>
class A
{
public:
    void foo() {};

    class B : private A<T>
    {
    public:
        typedef A<T> inherited;
        using inherited::foo;
    };
};

The code seems to be valid. Compilation output (the gcc_47_error.cpp file is
attached):
$ g++ --version
g++ (GCC) 4.7.0 20120205 (experimental)
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ g++ gcc_47_error.cpp
gcc_47_error.cpp:12:26: error: no members matching ‘A<T>::B::inherited::foo’ in
‘A<T>::B::inherited’

It compiles fine with gcc 4.6.2 and clang.
I'm using gcc built manually based on revision 183914.

My OS: Arch Linux:
$ uname -a
Linux alligator 3.2.2-1-ARCH #1 SMP PREEMPT Thu Jan 26 08:28:27 UTC 2012 i686
Intel(R) Pentium(R) 4 CPU 2.40GHz GenuineIntel GNU/Linux

[Bug c++/52126] [4.7 Regression] compilation error

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org,
                   |                            |jason at gcc dot gnu.org
   Target Milestone|---                         |4.7.0
            Summary|compilation error           |[4.7 Regression]
                   |                            |compilation error

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-02-05 20:28:32 UTC ---
Started with http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=182711

[Bug c++/52126] [4.7 Regression] compilation error

[tmmikolajczyk at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

--- Comment #2 from tmmikolajczyk at gmail dot com 2012-02-05 20:57:29 UTC ---
Further investigation shows that the issue appears only when inheritance from
the template class (class B : private A<T>) is provided explicitly. According
to the standard a nested class defined inside a class template is implicitly
template as well. The modified code reflecting that rule compiles fine:

template<typename T>
class A
{
public:
    void foo() {};

    class B : private A
    {
    public:
        typedef A inherited;
        using inherited::foo;
    };
};

Anyway, the first version of the code seems to be valid C++ code.

[Bug c++/52126] [4.7 Regression] compilation error

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

--- Comment #3 from fabien at gcc dot gnu.org 2012-02-06 21:31:30 UTC ---
I'll be assigning myself to this bug when I come back from vacation next
monday.

[Bug c++/52126] [4.7 Regression] compilation error

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
           Priority|P3                          |P1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-02-07
      Known to work|                            |4.6.3
     Ever Confirmed|0                           |1

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-02-07 15:46:32 UTC ---
Confirmed.

[Bug c++/52126] [4.7 Regression] compilation error

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-02-07 17:23:40 UTC ---
(In reply to comment #2)
> Further investigation shows that the issue appears only when inheritance from
> the template class (class B : private A<T>) is provided explicitly. According
> to the standard a nested class defined inside a class template is implicitly
> template as well.

I don't think that's relevant.  The point is that the injected-class-name 'A'
and 'A<T>' both refer to the class template, and should work equivalently.

It can be reduced to:

template<typename T>
struct A
{
    int foo;

    struct B : A<T>
    {
        using A::foo;
    };
};

[Bug c++/52126] [4.7 Regression] compilation error

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

fabien at gcc dot gnu.org changed:

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

[Bug c++/52126] [4.7 Regression] compilation error

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

--- Comment #6 from fabien at gcc dot gnu.org 2012-02-16 09:57:20 UTC ---
(In reply to comment #5)
> (In reply to comment #2)
> > Further investigation shows that the issue appears only when inheritance from
> > the template class (class B : private A<T>) is provided explicitly. According
> > to the standard a nested class defined inside a class template is implicitly
> > template as well.
> 
> I don't think that's relevant.  The point is that the injected-class-name 'A'
> and 'A<T>' both refer to the class template, and should work equivalently.

Yes, they should. The first bug is that 'A' does not behave like 'A<T>' -- I
have fixed it. The second bug is that 'A<T>' as a base for a nested class does
not currently work if A is also an enclosing class. I have tested a patch, but
it is not quite ready.

[Bug c++/52126] [4.7 Regression] compilation error

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

--- Comment #7 from fabien at gcc dot gnu.org 2012-02-17 07:49:43 UTC ---
Author: fabien
Date: Fri Feb 17 07:49:35 2012
New Revision: 184328

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=184328
Log:
gcc/testsuite/ChangeLog

2012-02-16  Fabien Chene  <fabien@gcc.gnu.org>

    PR c++/52126
    * g++.dg/template/using21.C: New.
    * g++.dg/template/using22.C: Likewise.

gcc/cp/ChangeLog

2012-02-16  Fabien Chene  <fabien@gcc.gnu.org>

        PR c++/52126
    * decl.c (xref_basetypes): call dependent_scope_p instead of
    dependent_type_p.

Added:
    trunk/gcc/testsuite/g++.dg/template/using21.C
    trunk/gcc/testsuite/g++.dg/template/using22.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/decl.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/52126] [4.7 Regression] compilation error

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52126

fabien at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #8 from fabien at gcc dot gnu.org 2012-02-17 07:51:44 UTC ---
Fixed in 4.7.