MISRA.CTOR.DYNAMIC

Object's dynamic type is used from the body of its constructor.

MISRA-C++ Rule 12-1-1 (required): An object"™s dynamic type shall not be used from the body of its constructor or destructor.

This rule is also covered by MISRA.DTOR.DYNAMIC.

[Undefined 10.4(6)]

Rationale

During construction and destruction of an object, its final type may be different to that of the completely constructed object. The result of using an object"™s dynamic type in a constructor or destructor may not be consistent with developer expectations.

The dynamic type of an object is used in the following constructs:

• typeid on a class with a virtual function or a virtual function in a base class.
• dynamic_cast
• A virtual call to a virtual function.

This rule also prohibits a call being made to a pure virtual function from within a constructor or destructor. Such calls lead to undefined behaviour.

Example

class B1
{
public:
   B1 ( )
   {
      typeid ( B1 );                    // Compliant, B1 not polymorphic
   }
};

class B2
{
public:
   virtual ~B2 ( );
   virtual void foo ( );
   B2 ( )
   {
      typeid ( B2 );                    // Non-compliant
      B2::foo ( );                      // Compliant — not a virtual call
      foo ( );                          // Non-compliant
      dynamic_cast< B2* > ( this );     // Non-compliant
   }
};