Chapter 38. Object Identity

Difficulty: 5

Who am I, really?” This problem addresses how to decide whether two pointers really refer to the same object.

The “this != &other” test (illustrated below) is a common coding practice intended to prevent self-assignment. Is the condition necessary and/or sufficient to accomplish this? Why or why not? If not, how would you fix it?

T& T::operator=( const T& other ) 
  if( this != &other )    // the test in question
    // ...
  return *this;

Remember to distinguish between “protecting against Murphy versus protecting against Machiavelli”—that is, protecting against things going wrong on their own versus a malicious programmer going to great lengths trying to break your code.


Short answer: In most cases, ...

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