Re: Partial implementation in derived classes

"Victor Bazarov" <>
Fri, 5 May 2006 10:46:30 -0400
Alex Vinokur wrote:

I tried to build program with partial implementation.
However a linker generates errors.

Is there any approach that enables to use partial implementation for
similar purposes?

------ foo.cpp ---
struct Base
 virtual void foo1() = 0;
 virtual void foo2() = 0;

struct Derived1 : public Base
 void foo1() {}
 void foo2(); // Not for use

struct Derived2 : public Base
 void foo1(); // Not for use
 void foo2() {}

int main ()
 Base* p1 = new Derived1();
 Base* p2 = new Derived2();
 // -----------------------
 // I would like to get linkage error in the following cases:
 // p1->foo2();
 // p2->foo1();
 // -----------------------
 return 0;
------ foo.cpp ---

------ Compilation ------
// gpp: GNU C++ 4.0.1 (DJGPP)

$ gpp foo.cpp

undefined reference to `vtable for Derived1'
undefined reference to `vtable for Derived2' collect2: ld returned 1
exit status

You're in violation of the Standard requirement: a virtual function shall
be either defined or declared pure (or both). You cannot have a virtual
function declared [normal] and not defined.

You could try accomplishing "partial implementation" if the functions you
don't want to define (and call) are _non-virtual_.

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