MISRA.CAST.PTR.VRCLASS

A cast form pointer to a virtual base class to pointer to a derived class does not use 'dynamic_cast'.

MISRA-C++ Rule 5-2-2 (required): A pointer to a virtual base class shall only be cast to a pointer to a derived class by means of dynamic_cast.

[Undefined 5.2.9(5, 8)]

Rationale

Casting from a virtual base to a derived class, using any means other than dynamic_cast has undefined behaviour. The behaviour for dynamic_cast is defined.

Example

class B { ... };
class D: public virtual B { ... };

D d;
B *pB = &d;
D *pD = static_cast<D*>(pB);    // Non-compliant - undefined behaviour
D *pD2 = dynamic_cast<D*>(pB);  // Compliant, but pD2 may be NULL
D & D3 = dynamic_cast<D&>(*pB); // Compliant, but may throw an exception