For the following classes, why is the output 1 instead of 10?:
class Top
{
public:
Top():a(1){}
Top(int arg):a(arg){}
virtual ~Top(){}
int a;
};
class Left : virtual public Top
{
public:
Left():b(2){}
int b;
};
class Right : virtual public Top
{
public:
Right(): c(3), Top(10){}
int c;
};
class Bottom : public Left, public Right
{
public:
Bottom():d(4){}
int d;
};
int main()
{
Bottom* bottom = new Bottom();
Right *right = bottom;
cout << "right->a: " << right->a << endl;
return 0;
} 4 2612 ch******@gmail. com wrote:
For the following classes, why is the output 1 instead of 10?:
....
>
class Right : virtual public Top
{
public:
Right(): c(3), Top(10){}
int c;
};
class Bottom : public Left, public Right
{
public:
Bottom():d(4){}
int d;
};
int main()
{
Bottom* bottom = new Bottom();
Right *right = bottom;
cout << "right->a: " << right->a << endl;
return 0;
}
The virtual base class constructor must be called
from the most derived constructor. In this case it must
be called from Bottom.
John.
John Grabner wrote:
ch******@gmail. com wrote:
For the following classes, why is the output 1 instead of 10?:
...
class Right : virtual public Top
{
public:
Right(): c(3), Top(10){}
int c;
};
class Bottom : public Left, public Right
{
public:
Bottom():d(4){}
int d;
};
int main()
{
Bottom* bottom = new Bottom();
Right *right = bottom;
cout << "right->a: " << right->a << endl;
return 0;
}
The virtual base class constructor must be called
from the most derived constructor. In this case it must
be called from Bottom.
John.
I know this is a bit of a digression from the OP's question but
shouldn't there be a delete Bottom; to avoid a memory leak? (I'm not
completely sure -- this is a genuine question, not a rhetorical one.)
Paul Epstein pa**********@at t.net wrote:
I know this is a bit of a digression from the OP's question but
shouldn't there be a delete Bottom; to avoid a memory leak? (I'm not
completely sure -- this is a genuine question, not a rhetorical one.)
Paul Epstein
In my opinion, yes and no. Yes, the memory needs to be deleted, but no,
not by delete. Here would be my main:
int main()
{
boost::shared_p tr<Rightright(b oost::shared_pt r<Bottom>(new
Bottom()));
cout << "right->a: " << right->a << endl;
return 0;
}
The shared_ptr cleans up for you when it goes out of scope.
Todd Gardner
The virtual base class constructor must be called
from the most derived constructor. In this case it must
be called from Bottom.
John.
So what happens to the explicit call to Top(10) in the initializer list
of class Right? Does it get called at all? This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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}
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