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The C++ Standard, [expr.delete], paragraph 3 [ISO/IEC 14882-2014], states the following:

In the first alternative (delete object), if the static type of the object to be deleted is different from its dynamic type, the static type shall be a base class of the dynamic type of the object to be deleted and the static type shall have a virtual destructor or the behavior is undefined. In the second alternative (delete array) if the dynamic type of the object to be deleted differs from its static type, the behavior is undefined.

...

Code Block

bgColor	#FFCCCC
lang	cpp

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

struct Derived final : Base {};

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

...

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:.

Code Block

bgColor	#ccccff
lang	cpp

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 that does not have a virtual destructor declared results in undefined destroy an array of polymorphic objects through the incorrect static type is undefined behavior. In practice, potential consequences include abnormal program termination and execution and memory leaks.