Hi Bill,
> class Sub1 : Base {
Probably should be:
class Sub1 : public Base {
> The question is, what happens when I call f() from g()? At -O3? Does
> it go though the usual vector dispatch table, does it call code for the
> same instance of f directly, does it inline f in g (separately for each
> subclass), or something else? Why? And, has it recently or is it going
> to change?
I presume the function call goes through the usual vector dispatch table.
But if you want to know for sure, compile with --save-temps and look at the
.s file.
There could be a SubSub1 : public Sub1, which extends Sub1. The compiler
does not know that there isn't.
If you want to get (or at least have the possibility of) inlining, you can
do this:
class Sub1
:
public Base
{
...
private:
void* f_impl(int a) // NOT virtual
{
code_f;
return something;
}
public:
virtual void* f(int a)
{
void* result = f_impl(a);
return result;
}
virtual void* g(int a)
{
code_g1;
void* r = f_impl(a+1);
code_g2;
return r;
}
}
Note carefully how that could affect SubSub1 (which may be adversely, or may
be beneficially... depends on the class and the method contract for f and g,
and if your team's convention of subclasses is to call their parent class
routines as well as doing their own additional behavior).
> Is there a reference I should have read rather than asking this question?
I recommend:
The C++ Programming Language (special edition) by Bjarne Stroustrup
C++ FAQ (2nd edition) by Cline, Lomow, and Girou
If you like reading standards documents:
ISO 14882
Sincerely,
--Eljay
