infer_clone/infer/documentation/issues/NIL_MESSAGING_TO_NON_POD.md

In Objective-C, calling a method on nil (or in Objective-C terms, sending a message to nil) does not crash, it simply returns a falsy value (nil/0/false). However, sending a message that returns a non-POD C++ type (POD being "Plain Old Data", essentially anything that cannot be compiled as a C-style struct) to nil causes undefined behaviour.

std::shared_ptr<int> callMethodReturnsnonPOD() {
  SomeObject* obj = getObjectOrNil();
  std::shared_ptr<int> d = [obj returnsnonPOD]; // UB
  return d;
}

To fix the above issue, we need to check if obj is not nil before calling the returnsnonPOD method:

std::shared_ptr<int> callMethodReturnsnonPOD(bool b) {
  SomeObject* obj = getObjectOrNil(b);
  if (obj == nil) { return std::make_shared<int>(0); }
  std::shared_ptr<int> d = [obj returnsnonPOD];
  return d;
}