They can result if you try to make a virtual function call from a constructor or destructor. Since you can't make a virtual function call from a constructor or destructor (the derived class object hasn't been constructed or has already been destroyed), it calls the base class version, which in the case of a pure virtual function, doesn't exist.
class Base
{
public:
Base() { reallyDoIt(); }
void reallyDoIt() { doIt(); } // DON'T DO THIS
virtual void doIt() = 0;
};
class Derived : public Base
{
void doIt() {}
};
int main(void)
{
Derived d; // This will cause "pure virtual function call" error
}
See also Raymond Chen's 2 articles on the subject
As well as the standard case of calling a virtual function from the constructor or destructor of an object with pure virtual functions you can also get a pure virtual function call (on MSVC at least) if you call a virtual function after the object has been destroyed. Obviously this is a pretty bad thing to try and do but if you're working with abstract classes as interfaces and you mess up then it's something that you might see. It's possibly more likely if you're using referenced counted interfaces and you have a ref count bug or if you have an object use/object destruction race condition in a multi-threaded program... The thing about these kinds of purecall is that it's often less easy to fathom out what's going on as a check for the 'usual suspects' of virtual calls in ctor and dtor will come up clean.
To help with debugging these kinds of problems you can, in various versions of MSVC, replace the runtime library's purecall handler. You do this by providing your own function with this signature:
int __cdecl _purecall(void)
and linking it before you link the runtime library. This gives YOU control of what happens when a purecall is detected. Once you have control you can do something more useful than the standard handler. I have a handler that can provide a stack trace of where the purecall happened; see here: http://www.lenholgate.com/blog/2006/01/purecall.html for more details.
(Note you can also call _set_purecall_handler() to install your handler in some versions of MSVC).
I've tried to start a match twice today and both times after matchmaking I've gotten the error: Fatal Error: Pure Function Call
The game worked fine yesterday and I haven't changed anything. Maybe a windows update? Is anyone else getting this error??
o/ what's up! Yep I got that error twice during my sesh yesterday. Only the 3rd time the game has crashed in my 70+ hours, maybe was some server issues?
No idea what it is but I had to disconnected error last night and two crashes late last night. To be fair I've only had a couple of crashes in around 100hrs but it's still a bit odd since i haven't changed anything in my system. Something to do with servers?