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Do not delete an array object through a static pointer type that differs from the dynamic pointer type of the object. Deleting an array through a pointer to the incorrect type, results in undefined behavior.

Noncompliant Code Example

In this noncompliant code example, an array of Derived objects is created and the pointer is stored in a Base *. Despite Base::~Base() being declared virtual, this still results in undefined behavior. Further, attempting to perform pointer arithmetic on the static type Base *, results in a violation of CTR39CTR56-CPP. Do not use pointer arithmetic on polymorphic objects.

struct Base {
  virtual ~Base() = default;
  virtual void f() {}
};

struct Derived final : Base {};

void f() {
   Base *b = new Derived[10];
   // ...
   delete [] b;
}

Compliant Solution

In this compliant solution, the static type of b is Derived *, which removes the undefined behavior when indexing into the array as well as when deleting the pointer:

struct Base {
  virtual ~Base() = default;
  virtual void f() {}
};

struct Derived final : Base {};

void f() {
   Derived *b = new Derived[10];
   // ...
   delete [] b;
}

Risk Assessment

Attempting to destruct a polymorphic object which does not have a virtual destructor declared results in undefined behavior. In practice, potential consequences include abnormal program termination and memory leaks.

Automated Detection

Related Vulnerabilities

Search for other vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

Bibliography

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