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Calling a pure virtual function
- From: Adam Nielsen <a dot nielsen at shikadi dot net>
- To: gcc at gcc dot gnu dot org
- Date: Sat, 9 Jul 2005 20:41:47 +1000
- Subject: Calling a pure virtual function
Hi all,
I was expecting the following code snippet to work, so am I doing
something wrong, or is there an issue with GCC? I was under the
impression that this is allowed, according to
http://www.parashift.com/c++-faq-lite/strange-inheritance.html#faq-23.1
It seems like GCC initially allows it as it starts to compile okay, but
then I get an undefined reference error from the linker (because it
seems to be actually calling Base::number(), which obviously won't work
as it's a pure virtual function.)
I was only able to try this with GCC 3.2.3 (i486 target) and 3.3.6
(djgpp/msdos target) and both versions give the same error.
Thanks,
Adam.
------------------------------------------------------
#include <iostream>
using namespace std;
class Base {
public:
Base()
{
cout << "This is class " << this->number();
}
virtual int number() = 0;
};
class One: virtual public Base {
public:
int number()
{
return 1;
}
};
int main(void)
{
// Correctly fails stating Base is abstract
// Base *b = new Base();
// Won't compile giving undefined reference to Base::number()
One *o = new One();
return 0;
}