What is Data Type of Vptr pointer

[Veeru]

Hi ,
What is the data type of Vptr pointer used in the virtual funtion
mechanism?
i suppose its void. Please correct me if i am wrong...

Regards,
Veeru

 

[Victor Bazarov]

What is the data type of Vptr pointer used in the virtual funtion
mechanism?
i suppose its void. Please correct me if i am wrong...

Not sure what 'Vptr' you mean. Do you mean 'vtbl'? If so, it is not
defined in C++. It's an ipmlementation detail, and as such has no
representation/definition in C++ proper.

V

 

[Murali Krishna]

Hi ,
What is the data type of Vptr pointer used in the virtual funtion
mechanism?
i suppose its void. Please correct me if i am wrong...

Regards,
Veeru

your question was answered in Marshall Cline's FAQs

see this..
http://www.parashift.com/c++-faq-lite/virtual-functions.html#faq-20.4

-- Murali Krishna

 

[Veeru]

your question was answered in Marshall Cline's FAQs

see this..
http://www.parashift.com/c++-faq-lite/virtual-functions.html#faq-20.4

-- Murali Krishna

i searched in the FAQ but didnt find the answer to my question. i
wanted to know the data type of the Vptr pointer the points to the
Vbtl(virtual table) which contains the function pointers to virtual
functions.

Please help.

Regards,
Veeru

 

[Murali Krishna]

i searched in the FAQ but didnt find the answer to my question. i
wanted to know the data type of the Vptr pointer the points to the
Vbtl(virtual table) which contains the function pointers to virtual
functions.

Please help.

Regards,
Veeru

I think you have faced this in an interview. I have not seen about
VPtr's data-type till now. but as written in FAQs, you can understand
that it is a generic pointer (say void*) to a generic member function
because it stores the starting address of the V-Table.

I guess it is void*.

-- Murali Krishna.

 

[Veeru]

I think you have faced this in an interview. I have not seen about
VPtr's data-type till now. but as written in FAQs, you can understand
that it is a generic pointer (say void*) to a generic member function
because it stores the starting address of the V-Table.

I guess it is void*.

-- Murali Krishna.

Thanks Murali for such a quick response.
There are two possibilities as far as i can see now:
1. Either Vptr could be a void *
OR
2. V-Table must be some kind of an internal hidden sturture or class.
And the Vptr points to the V-Table. So Vptr could have a data type of
V-Table.

Well, this is just what i can guess.
But still need a confimation.

Regards,
Veeru

 

[Kai-Uwe Bux]

Thanks Murali for such a quick response.
There are two possibilities as far as i can see now:
1. Either Vptr could be a void *
OR
2. V-Table must be some kind of an internal hidden sturture or class.
And the Vptr points to the V-Table. So Vptr could have a data type of
V-Table.

Well, this is just what i can guess.
But still need a confimation.

There is no way to confirm this: the c++ standard does not even require that
v-tables exist. In particular, it does not prescribe the types and data
structures used to implement the dispatch mechanism for virtual functions.
Thus, your question does not have a general answer. If you are interested
in how a given implementation does it, then you should ask your question in
a forum dedicated to that particular implementation.


Best

Kai-Uwe Bux

 

[tragomaskhalos]

Hi ,
What is the data type of Vptr pointer used in the virtual funtion
mechanism?
i suppose its void. Please correct me if i am wrong...

Your question actually makes no sense - virtual function dispatch is a
language internal feature, and as such has nothing to do with the type
system.