Thanks Bob and Frank, indeed that was it. The most derived class must
explicitly invoke the virutal base class's constructor.
Great
thanks both
klaas
Frank wrote:
> I think BobR gave the correct solution. In this case, virtual
> inheritance makes the constructor of "base" delay to the most derived
> class "'doublederived" and suppresses the call of it from "derived".
> Actually, in the constructor of " base", if you don't invoke the
> constructor of "base", its default constructor will be the first
> candidate.
>
> "BobR 写道：
> "
>> Klaas Vantournhout wrote in message
>> <4560e845$0$1120$>...
>>> Hi,
>>>
>>> Recently I obtained a problem with virtual inheritance when implementing
>>> it in multiple files. To present the problem I have included at the
>>> bottom of this post the code of the 4 files. I show results with the
>>> gnu compiler but i have the same results with the intel compiler.
>>>
>>> file1.cpp compiles without a problem, the problem occurs when compiling
>>> file2.cpp. It complains about not finding the constructor of the class
>>> base.
>>>
>>> [klaas@blackdwarf cpptest]$ g++ -c -Wall file2.cpp
>>> file2.cpp: In constructor 'doublederived::doublederived(int)':
>>> file2.cpp:3: error: no matching function for call to 'base::base()'
>>> file1.hpp:3: note: candidates are: base::base(int)
>>> file1.hpp:1: note: base::base(const base&)
>>>
>>> When derived does not virtual inherit base, this does not give a
>>> problem. Is there a reason why this is not working?
>>>
>>> Regards
>>> Klaas
>>>
>>> // file1.hpp
>>> class base {
>>> public:
>>> base(int);
>>> };
>>>
>>> class derived : public virtual base {
>>> public:
>>> derived(int);
>>> };
>>>
>>> // file1.cpp
>>> #include <iostream>
>>> #include "file1.hpp"
>>> base::base(int a) { std::cout << a << std::endl;}
>>> derived::derived(int a) : base(a) { }
>>>
>>> // file2.hpp
>>> #include "file1.hpp"
>>> class doublederived : public derived {
>>> public:
>>> doublederived(int);
>>> };
>>>
>>> // file2.cpp
>>> #include "file2.hpp"
>>> doublederived::doublederived(int a) : derived(a) { }
>> I'm not real sharp on this one. I looked at Eckel's and found this (in
>> diamond example):
>>
>> class Left : virtual public Top { public: <snip>
>> Left(int m, int n) : Top(m) { y = n; }
>> };
>>
>> class Right : virtual public Top { public: <snip>
>> Right(int m, int n) : Top(m) { z = n; }
>> };
>>
>> class Bottom : public Left, public Right {
>> int w;
>> public:
>> Bottom(int i, int j, int k, int m)
>> : Top(i), Left(0, j), Right(0, k) { w = m; }
>> };
>>
>> Note how, even though Bottom did not directly derive from Top, it was still
>> initialised in Bottom.
>>
>> So, maybe try(?):
>>
>> doublederived::doublederived(int a) : base(a), derived(a) { }
>>
>> Makes since to me because your error is in looking for a base default
>> constructor, instead of using your defined constructor.
>>
>> I'm just guessing at this, but, it shouldn't hurt to try it.
>> I tried it (in a single file) and it worked.
>>
>> --
>> Bob R
>> POVrookie
>
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