calling pure virtual

##### [11:08:10] # [dare2be@PC10CIS:/tmp] #####
$ cat b.cpp
class B {
public:
  B() { f1(); }
  // call from ctor to “impure” virtual; looks safe
  virtual void f1() { f3(10); } // call to pure virtual from non-ctor; looks safe
  virtual void f3(int x) = 0;
};

class D : public B {
  void f3(int x) {}
};

int main() {
  D d;
  return 0;
}
##### [11:08:24] # [dare2be@PC10CIS:/tmp] #####
$ g++ -Wall b.cpp -o b
##### [11:08:35] # [dare2be@PC10CIS:/tmp] #####
$ ./b
pure virtual method called
terminate called without an active exception
Aborted