Re: // how can I access A::a?

From:

Victor Bazarov <v.bazarov@comcast.invalid>

Newsgroups:

comp.lang.c++

Date:

Tue, 12 Apr 2011 15:01:57 -0400

Message-ID:

<io27j5$3v1$1@dont-email.me>

On 4/12/2011 2:20 PM, Pete Becker wrote:

On 2011-04-12 13:34:19 -0400, Victor Bazarov said:

On 4/12/2011 7:38 AM, Pete Becker wrote:

On 2011-04-11 18:52:40 -0400, dick said:

/* multi_level_inheritance.cpp */
struct A
{
int a;
};

struct B1 : public A
{
int a;
};

struct B2 : public A
{
int a;
};

struct C : public B1, public B2
{
int a;
};

int main()
{
C ccc;

ccc.a=123;

ccc.B1::a=456;

/* 0030 */ ccc.B1::A::a=789;

}

// c++ multi_level_inheritance.cpp
// multi_level_inheritance.cpp: In function int main():
// multi_level_inheritance.cpp:30: error: A is an ambiguous base of C

// how can I access A::a?

There are two A::a's, which is why the error message said that the
reference to A is ambiguous. You need to decide which one you want to
access, then name it. Hint: there's one in B1 and one in B2.

And does the fact that the OP specifically used 'B1::' before 'A::a'
matter not?

Sure, but you're giving away the ending. There's clearly a problem in
the line ccc.a = 123; so it's not at all likely that the only error
message came from the line marked /* 0030 */.

Actually, since 'C' has a member 'a', which hides *both* 'B1::a' and
'B2::a' (which in turn hid both 'A::a' from base class 'A'), I would not
expect to see an error in 'ccc.a = 123;'. Just saying...

On the other hand, it does help to carefully read the code in question. :-(

V
--
I do not respond to top-posted replies, please don't ask