finally_delete -- Adapt old C object to RAII.

finally_delete.hpp

// adapt old C object to RAII
// Example:
// ```
//    Object* object_pointer = nullptr;
//    finally_delete(object_pointer, delete_function)
//    auto* object_pointer = allocate_some_object();
//    throw exception/return;
// ```

template <typename objectPointer, typename delete_function>
struct finally_delete_implementation {
  finally_delete_implementation(objectPointer& o, delete_function f)
      : o(o), f(f) {}
  ~finally_delete_implementation() {
    if (o) {
      f(o);
      o = nullptr;
    }
  }
  objectPointer& o;
  delete_function f;
};

template <typename objectPointer, typename delete_function>
finally_delete_implementation<objectPointer, delete_function>
finally_delete_function(objectPointer& o, delete_function f) {
  return finally_delete_implementation<objectPointer, delete_function>(o, f);
}

#define finally_delete(object_pointer, delete_function) \
  finally_delete_helper_1(object_pointer, delete_function, __LINE__)
#define finally_delete_helper_1(object_pointer, delete_function, line) \
  finally_delete_helper_2(object_pointer, delete_function, line);
#define finally_delete_helper_2(object_pointer, delete_function, line) \
  const auto& finally_delete_##line =                                  \
      finally_delete_function(object_pointer, delete_function)