"Undefined reference to '__cxa_pure_virtual'" error message

I'm getting an undefined reference to '__cxa_pure_virtual' error when linking. What does this mean?

The __cxa_pure_virtual function is an error handler that is invoked when a pure virtual function is called.

If you are writing a C++ application that has pure virtual functions you must supply your own __cxa_pure_virtual error handler function. For example:

extern "C" void __cxa_pure_virtual()
{
  while (1);
}