Rule Definition
By implementing class interfaces with member functions the implementation retains more control over how the object state can be modified and helps to allow a class to be maintained without affecting clients. Returning a handle to class-data allows for clients to modify the state of the object without using any interfaces.

Remediation
A resource can be used by the class but is not class-data, non-const handles to this data may be returned.

Violation Code Sample

class C
{
public:
int32_t & getA () // Non-compliant
{
return a;
}
private:
int32_t a;
};
void b ( C & c )
{
int32_t & a_ref = c.getA ();
a_ref = 10; // External modification of private C::a
}



c.getA() returns a reference to the member, which is then stored and modified by a_ref. The
class, therefore, has no control over changes to its state.

Fixed Code Sample

class C
{
public:
C ( int32_t * shared ) : m_shared ( shared )
{
}
int32_t * getA ()
{
return m_shared; // Compliant - m_shared is not class-data
}
private:
int32_t * m_shared;
};

MISRA C++ 2008, 9-3-2: Member functions shall not return non-const handles to class-data. AUTOSAR C++ 2014, A9-3-1: Member functions shall not return non-const “raw” pointers or references to private or protected data owned by the class.