[Bug c++/19189] New: A derived template cannot access base template members without using this

[Bug c++/19189] New: A derived template cannot access base template members without using this

[amos at ilogix dot com]

If you try to access a member of a base template from a derived template (event
if the member is public) you are getting a compilation error.
This is a regression related to previous versions of the compiler (worked in
3.3.3) and I think its not ANSI C++ as well.

For example, compiling the following code (in test.cpp) will issue these errors:
$ g++ -c test.cpp 
test.cpp: In member function `virtual bool Derived<Concept>::test(Concept)':
test.cpp:21: error: `xxx' undeclared (first use this function)
test.cpp:21: error: (Each undeclared identifier is reported only once for each f
                                               unction it appears in.)

------------
test.cpp
------------
// The base template
template <class Concept> class Base 
{
public :
    int xxx;     
};

// The derived template
template <class Concept> class Derived : public Base<Concept> 
{
public :
	bool test(Concept p)
	{
        return (xxx > 10); // to fix this I need to modify it to: return
(this->xxx > 10);
    }
};

// usage
bool call_test(Derived<int>& d)
{
	return d.test(5);
}

-- 
           Summary: A derived template cannot access base template members
                    without using this
           Product: gcc
           Version: 3.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: amos at ilogix dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: gcc version 3.4.2 (mingw-special)
  GCC host triplet: MinGW on WinXP
GCC target triplet: MinGW on WinXP


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19189

[Bug c++/19189] A derived template cannot access base template members without using this

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-12-29 14:33 -------
Does anyone read the release notes?

Yes this is required by the C++ standard.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19189

[Bug c++/19189] A derived template cannot access base template members without using this

[pinskia at physics dot uc dot edu]

------- Additional Comments From pinskia at physics dot uc dot edu  2004-12-29 14:58 -------
Subject: Re:  A derived template cannot access base templat e members without using this


On Dec 29, 2004, at 9:54 AM, Amos Ortal wrote:

> Hi Andrew,
>
> Thank you for your fast reply, I saw the entry in the release notes 
> but it doesn't point to the standard and I could not find it.
>
> Can you please point me to the section in the standard that specify 
> this?

14.6, the whole section is about name resolution in templates.

-- Pinski



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19189

[Bug c++/19189] A derived template cannot access base template members without using this

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-12-29 16:59 -------
Specifically, [temp.dep]/3. Besides, even if the release notes do not point you 
to a specific place in the standard, the fact that we even documented that it's 
a *wanted* change in behaviour, it means it has to be correct, don't you think?

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19189

[Bug c++/19189] A derived template cannot access base template members without using this

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-12-29 17:04 -------
BTW, I just added the standard reference to the release notes as well.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19189

[Bug c++/19189] A derived template cannot access base template members without using this

[amos at ilogix dot com]

------- Additional Comments From amos at ilogix dot com  2004-12-30 07:32 -------
(In reply to comment #3):
I agree that this is the expected behavior, although such a change, without any
backward compatibility, makes it hard to upgrade to a new version of the compiler.
In our specific case, we provide a generic library and a client that tried to
upgrade found the error and didn't understand why (they didn't read the release
notes as well). Also the error message doesn't help you to understand that this
is a deliberate change.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19189