[Bug c++/29470] New: Using declaration access semantics change with templates

["spam at david dot osborn dot name" <gcc-bugzilla at gcc dot gnu dot org>]

In the following class template, the protected using declaration causes the
inherited member to become publicly accessible.  The code compiles, even though
it shouldn't.

template <typename T> struct B
{
        protected:
        T v;
};
template <typename T> struct D : B<T>
{
        protected:
        using B<T>::v;
};
int main()
{
        D<int> d;
        d.v = 0;
        return 0;
}

$ g++ test.cpp

The same code without templates gives the correct behaviour and doesn't
compile.

struct B
{
        protected:
        int v;
};
struct D : B
{
        protected:
        using B::v;
};
int main()
{
        D d;
        d.v = 0;
        return 0;
}

$ g++ test.cpp
test.cpp: In function 'int main()':
test.cpp:4: error: 'int B::v' is protected
test.cpp:14: error: within this context

The preprocessed file from the template version is as follows:

# 1 "test.cpp"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "test.cpp"
template <typename T> struct B
{
 protected:
 T v;
};

template <typename T> struct D : B<T>
{
 protected:
 using B<T>::v;
};

int main()
{
 D<int> d;
 d.v = 0;
 return 0;
}


-- 
           Summary: Using declaration access semantics change with templates
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: spam at david dot osborn dot name
 GCC build triplet: i686-pc-mingw32
  GCC host triplet: i686-pc-mingw32
GCC target triplet: i686-pc-mingw32


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29470