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NNTP-Posting-Date: Tue, 12 Apr 2011 13:20:07 -0500
From: Pete Becker <pete@versatilecoding.com>
Organization: Roundhouse Consulting, Ltd.
Newsgroups: comp.lang.c++
Date: Tue, 12 Apr 2011 14:20:06 -0400
Message-ID: <2011041214200693759-pete@versatilecodingcom>
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Subject: Re: // how can I access A::a?
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.c++:3506

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 */.

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

-- 
  Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The 
Standard C++ Library Extensions: a Tutorial and Reference 
(www.petebecker.com/tr1book)