virtual and sizeof

[jackandking]

class A{
virtual void foo(){};
};sizeof(A)=1

class B : public virtural A{
virtual void foo(){};
};
sizeof(B)=? and why

[kbw]

http://www.cprogramming.com/tutorial/size_of_class_object.html

[jsmith]

Undefined by the standard, IIRC (even though the tutorial leads you to believe otherwise).

[guestgulkan]

class A{
virtual void foo(){};
};sizeof(A)=1 //Why do you think sizeof A  will be 1   ?? 

[jackandking]

sorry for my thoughtless, sizeof(A)=4.

Actually, I am confused by:
class C : public A{
virtual void foo(){};
};

how about sizeof(C)=?
what's the difference between B and C?

[writetonsharma]

read

inside c++ object model

and clear all doubts.. :)

[guestgulkan]

The difference between Class B and Class C is in the way they inherit from Class A.

class A

class B : public virtual A

class C : public A

The important bit is that word virtual it adds an extra virtual function pointer to Class B.
So you will probably find Class A is size 4, Class B is size 8 and Class C is size 4

[jackandking]

guestgulkan,

I am afraid that sizeof(B)=4.

[guestgulkan]

Compiler specific?

4 8 4 microsoft;
4 4 4 mingw_g++