MacArthur, Ian (SELEX GALILEO, UK) wrote:
> Also, can someone tell me... For a "fast" and "light" toolkit, is there
> a performance impact with the overloading and virtual functions?
Not with overloading, overloads are just different functions (which
happen to share similar name) and the resulting machine code is the same
as if you would use different names.
As Fabien writes elsewhere, virtual functions are somewhat slower due to
additional dereferencing through vtable pointer and also normaly can not
be inlined - exception might be situation when you explicitly use
particular incarnation of virtual function like
class Derived: public Base{
void do_something(){
Base::do_comething(); // could be inlined
do_something_else();
}
}
which could be inlined if the code for the base function is available
and appropriate compiler optimisation switches are set.
Nevertheless the penalty for virtualisation is small if the function is
not really primitive one and you do not call it in some google loop, it
hardly matters. And if you need a "virtual" functionality in some form,
you do not have too many options - any codding around would be probably
much worse.
R.
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