Question

Let’s assume I have a c++ class that have properly implemented a copy constructor and an overloaded = operator. By properly implemented I mean they are working and perform a deep copy:

Class1::Class1(const Class1 &class1)
{
  // Perform copy
}
Class1& Class1::operator=(const Class1 *class1)
{
  // perform copy
  return *this;
}

Now lets say I have this constructor as well:

Class1::Class1(Class1 *class1)
{
   *this = *class1;
}

My question is would the above constructor be acceptable practice? This is code that i’ve inherited and maintaining.

Answer 1

I would say, “no”, for the following reasons:

• A traditional copy constructor accepts its argument as a const reference, not as a pointer.
• Even if you were to accept a pointer as a parameter, it really ought to be const Class1* to signify that the argument will not be modified.
• This copy constructor is inefficient (or won’t work!) because all members of Class1 are default-initialized, and then copied using operator=
• operator= has the same problem; it should accept a reference, not a pointer.

The traditional way to “re-use” the copy constructor in operator= is the copy-and-swap idiom. I would suggest implementing the class that way.