Re: Pure virtual function call in Winamp?
"Robbie Hatley" <lonewolf@well.com> wrote in
news:0cGdnaaabt2ruHzXnZ2dnUVZ_j-dnZ2d@giganews.com:
So I think something in this one program is, under a very particular
set of circumstances, trying to call the base-class version of a
pure virtual function.
My reason for posting this *here* is to see if anyone has actually
run into bugs like this, either in their own code, or someone else's.
Being a C++ developer myself, it seems to me a very unusual bug;
something like that would normally be caught early in alpha testing,
I should think.
You cannot test for everything, especially if the problem appears in a
"very particular set of circumstances".
I have definitely seen that bug myself, mostly in my own code during
development. In my code, the bugs were always caused by too complex data
structures, where child objects had backlink pointers or references to
their parents, and the object lifetimes were not entirely clear. The
following example ought to exhibit the bug, about once per each 10 runs.
#include <iostream>
#include <stdlib.h>
#include <time.h>
#include <string>
bool BadMoonPhase() {
return rand()%10 == 0;
}
class X {
public:
virtual ~X() {}
};
class A {
public:
A(): x_(NULL) {}
void SetX(X* x) {x_ = x;}
virtual std::string Description() const=0;
virtual ~A() {
delete x_;
}
private:
X* x_;
};
class Y: public X {
public:
Y(A& parent): parent_(parent) {}
std::string Description() const {
return "Y, inside of a " + parent_.Description();
}
~Y() {
if (BadMoonPhase()) {
std::cerr << "Bad moon phase discovered by: ";
std::cerr << Description() << "\n";
}
}
private:
A& parent_;
};
class B: public A {
public:
B() {
SetX(new Y(*this));
}
virtual std::string Description() const { return "B object";}
};
int main() {
srand(time(NULL));
B b;
}