Synopsis

Assignment operator does not check for self-assignment before allocating member functions

Enabled by default

Yes

Severity/Certainty

Medium/High

Full description

An assignment operator does not check for self-assignment before allocating member functions. If self-assignment occurs in a user-defined object which uses dynamic memory allocation, references to allocated memory will be lost if they are reassigned. This will most likely cause a memory leak, as well as unexpected results, because the objects referred to by any pointers are lost.

Coding standards

Code examples

The following code example fails the check and will give a warning:

class MyClass{
  int* p;
  MyClass& operator=(const MyClass& rhs){
    p = new int(*(rhs.p));  //reference to the old 
                            //memory is lost
    return *this;
  }
};

The following code example passes the check and will not give a warning about this issue:

class MyClass{
  int* p;
  MyClass& operator=(const MyClass& rhs){
    if (&rhs != this)  //the pointer is not reallocated
                       //if the object is assigned to itself
      p = new int(*(rhs.p));
    return *this;
  }
};