> What will be the size of a class with no instance variable ?
>
I read your question wrongly as "What will be the size of a class with no
instance". So replying again.
I would say that the question "What will be the size of a class with no
instance variable?" is not specific. So there are different answers.
1. The size of a class with no "non-static member variable" (I think this term
is correct),
which doesn't inherit any other class and doesn't have any virtual functions in
it is 1. (The least possible integer)
2. The size of a class with no non-static member variable, which inherits other
classes and has virtual functions.
This depends on the size of the immediate base class(s) and also
depends on if virtual
functions are present in that class or in any of the base classes. In
the following
example, eventhough there are no non-static member variables in the
class and in any of
the base classes, the size is 8 because the virtual base class pointer
adds a 4 bytes
overhead in each virtual inheritance.
#include <iostream>
using namespace std;
class Base
{
};
class Interm1: public virtual Base
{
};
class Interm2: public virtual Base
{
};
class Derived: public Interm1, public Interm2
{
};
int main()
{
cout << sizeof(Derived);
return 0;
}
If there are virtual functions in the class or in any of the base classes,
there will be a 4
bytes overhead, which is the sizeof(vptr).
class ABC
{
virtual void function1()
{
}
};
int main()
{
cout << sizeof(ABC);
return 0;
}
Regards,
Jos Collin
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