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V794. The assignment operator should be…
Analyzer Diagnostics
General Analysis (C++)
General Analysis (C#)
General Analysis (Java)
Diagnosis of micro-optimizations (C++)
Diagnosis of 64-bit errors (Viva64, C++)
MISRA errors
AUTOSAR errors
Additional information
Contents

V794. The assignment operator should be protected from the case of this == &src.

June 1, 2017

The analyzer has detected a dangerous copy assignment operator that lacks a check for object self-assignment and at the same time contains operations that could cause memory leaks, use of deallocated pointers, and other problems, in case it receives a reference to '*this' as an argument.

Consider the following example:

class C {
  char *p;
  size_t len;
public:
  C& operator = (const C& other) {
    delete p;
    len = other.len;
    p = new char[len];
    std::copy(other.p, other.p + len, p);
    return *this;
  }
};

The error will show if 'this == &other' and, therefore, 'p == other.p'. In that case, the uninitialized array will be copied into itself when the 'std::copy' call is executed.

Fixed code:

C& operator = (const C& other) {
  if (this == &other)
    return *this;
  delete p;
  len = other.len;
  p = new char[len];
  std::copy(other.p, other.p + len, p);
  return *this;
}

If, however, you know that no such situation can occur, i.e. the operator has an implicit contract, it is recommended that you formalize this contract as an 'assert' construct:

C& operator = (const C& other) {
  MyAssert(this != &other);
  ....
}

You can look at examples of errors detected by the V794 diagnostic.

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