Issue with using and const overloaded methods in GCC 3.0.3

Issue with using and const overloaded methods in GCC 3.0.3

[Hunter, David J]

The following code

struct A
{
   A( ) { }

    const void a( ) const { }  // Line A
          void a( )       { }        // Line B
};

struct B : public A
{
    B( ) : A( ) { }

    using A::a;
};

int main( unsigned int, char** )
{
    B b1;

    b1.a( );

    const B b2;

    b2.a( );
}

produces the error  "Test.c:XX: passing `const B' as `this' argument of
`void A::a()' discards qualifiers",
which seems to suggest that only the non const version of the method A::a is
brought into the B scope
by the using declaration in B. The error disappears when the line A and B
are reversed which seems
to imply that only the first A::a, whichever it is, is being brought into
scope B.

My understanding of the using declaration in B is that it should bring both
A::a methods into the B scope
and that the const resolution should work fine, am I in error in this or is
the compiler?

Note that I have test on GCC 3.0.3 on Linux 7.2 and Solaris 8. This code
compiles fine on Forte 6 update
2 on Solaris.

David Hunter






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Re: Issue with using and const overloaded methods in GCC 3.0.3

[Oliver Kullmann]

> The following code
>
> struct A
> {
>    A( ) { }
>
>     const void a( ) const { }  // Line A
>           void a( )       { }        // Line B
> };
>
> struct B : public A
> {
>     B( ) : A( ) { }
>
>     using A::a;
> };
>
> int main( unsigned int, char** )
> {
>     B b1;
>
>     b1.a( );
>
>     const B b2;
>
>     b2.a( );
> }
>
> produces the error  "Test.c:XX: passing `const B' as `this' argument of
> `void A::a()' discards qualifiers",
> which seems to suggest that only the non const version of the method A::a is
> brought into the B scope
> by the using declaration in B. The error disappears when the line A and B
> are reversed which seems
> to imply that only the first A::a, whichever it is, is being brought into
> scope B.
>
> My understanding of the using declaration in B is that it should bring both
> A::a methods into the B scope
> and that the const resolution should work fine, am I in error in this or is
> the compiler?
>
> Note that I have test on GCC 3.0.3 on Linux 7.2 and Solaris 8. This code
> compiles fine on Forte 6 update
> 2 on Solaris.
>
> David Hunter
>
>

Using g++, version 3.0.4 (the current stable version) the code also compiles without
problems. Considering section 7.3.3 on the the using declaration in ISO/IEC 14882:1998(E)
(especially the example on top of page 119), furthermore that in general a cv-qualified type
(that is, a type qualified with "constant" or "volatile") is a different type than the corresponding
unqualified type, and given the rules for function overloading, I also think your interpretation
is right (and thus also version 3.0.4 is correct here).

Oliver