Michael P. O'Connor

Ug, the hard drive on my Linux box seems to be having some major problems, Bad sectors and all. So what I am trying to do, is since it only is happening on the /home partion, and that partion is 100Gb large and I only have 30Gb of data on it, and the problem seems to be at the beginning of the partion, I backed up the data, then did the /home partion to partion out the bad block area from the file system. When I finish formating the new /home partion, I will restore my files. But till then my Linux box is a bit down :-(. The partion will be will finish formating soon (I run the badblock check on it as I format) then I will get the data to restore, it should be finished by the time I get back from my churches Super Bowl party.

In my last post, I talked about using Virtual Class Inheritance, and was thinking about how to cast it.

well I have come up with from books and talking with others to try this:
[code]
// See http://blog.mikeoconnor.net/?postid=874
// for the class defs

grandchild* Base2grandchild(Base *ptr)
{
grandchild *toBeReturned;
try
{
toBeReturned = dynamic_cast(ptr);
return toBeReturned;
}
catch(…)
{
// cast failed deal with it
}
return NULL;
}
[/code]
So it looks like what needs to be done.

I am going to post some evil now, I will cover more on it later.

But a program I am working on has gotten to a point to where I ended up needing to do something like
[code]
class Base
{
public:
int value
};
class child1 : public Base { };
class child2 : public Base { };
class grandchild : public child1, public child2
{
public:
grandchild() { /* I want to access value here */ };
};
[/code]
Now with the above I can not access value directly I have to say which value I want since it comes down twice I have it as both child1::value and child2::value. Well I looked around to see what I can do with this problem, I found out about Virtual Base Classes so to deal with it check out the code below
[code]
class Base
{
public:
int value
};
class child1 : public Base { };
class child2 : public Base { };
class grandchild : virtual public child1, virtual public child2
{
public:
grandchild() { value };
};
[/code]
Now the above does work, the virtual keyword in the inheritance causes the grandchild object to get only one copy of the Base class so I can get to value just like if there was only one path to the Base class.
The problem I am dealing with is assume I now have a virtual function call getWhatAmI() that returns info that I can use to know what type of object I am working on, so I end up in a portion of the code where I have a grandchild object being pointed to by a Base pointer. I have an if statement that only happens if I am working with a grandchild object, now I have to cast back to a grandchild so I have access to the grandchild objects. But I can not just cast it any more I get the error of [code]
“error C2635: cannot convert a ‘Base*’ to a ‘grandchild*’; conversion from a virtual base class is implied”
[/code]
So now I have to find out how to cast with this virtual base class stuff.
I will post the solution when I find a good one.