Re: Question about interfaces
On Jun 28, 4:36 pm, sip.addr...@gmail.com wrote:
[...]
But we could also use private inheritance:
class Imp1 {
protected:
void f();
void g();
};
class Interface : private Imp1 {
public:
void f() { Imp1::f(); }
...
};
What are the advantages/disadvantages of each?
Normally, interfaces have more than one implementation as in Cat and
Dog inheriting from the Animal interface. So your private
implementation inheritance wouldn't work.
I believe in both cases
a level of indirection happens (through the virtual table or calling
the base class function in the second case). But probably today
compilers do some optimizations?
Sometimes, when the actual type of the object is known at compile time
I guess. Otherwise, in general the actual type is not known without
the use of virtual function table.
At a recent ACCU Silicon Valley talk, Ulrich Drepper mentioned how
indirect calls like C++'s virtual functions hurt the CPU's caching
schemes. Something to keep in mind, but I am not getting rid of my
virtual functions yet... :)
Ali