Abstract base class with pure virtual functions

If i have an abstract base class, that only contains pure virtual methods
(and maybe some non-virtual methods), is a vtable still being generated,
for the first derived class that implements those pure virtuals? My idea is
that as long as there are less than two virtual methods of the same name in
existance, it would (in theory) not be necessary to build a vtable, thus
eliminating the need for a lookup during runtime.

Arne

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re: Abstract base class with pure virtual functions

Arne Schmitz wrote:
And how are you going to call the Single virtual member via pointer to
its base class?

re: Abstract base class with pure virtual functions

Arne Schmitz wrote:"Less than two virtual method of the same name in existance"? Could
you please elaborate? The 'vtable' method of implementing virtual
function mechanism has nothing to do with the number of identically
named functions in existence. Besides, if I derive from your class
and override one of them, and then do it again, and again, how (or
why) would it affect the way _your_ class is implemented?

V
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re: Abstract base class with pure virtual functions

Victor Bazarov wrote:
Yes, I just realised that virtual member functions are implementation
dependent. This and your other comment answered my question. :)

Thanks,

Arne

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re: Abstract base class with pure virtual functions

Arne Schmitz wrote:You should still implement a (pure) virtual dtor.
Note that even if it's abstract, you still need to provide a dtor
definition.

e.g.

Having this in your header:

class abstract {
virtual void foo() = 0;
virtual ~abstract() = 0;
};

Put this in your implementation file:

abstract::~abstract() {
}