Question

I am not sure whether I am missing something basic. But I am unable to understand why the compiler is generating the error for this code:

class A { };  class B { public:     B();     A* get() const;  private:     A* m_p; };  B::B() {     m_p = new A; }  A* B::get() const {     //This is compiling fine     return m_p; }  class C { public:     A* get() const; private:     A m_a; };  A* C::get() const {    //Compiler generates an error for this. Why?      return &m_a; } 

EDIT: The compiler error is : error C2440: ‘return’ : cannot convert from ‘const class A *’ to ‘class A *’ Conversion loses qualifiers

Answer 1

const in the function signature tells the compiler that the object’s members may not be modified. Yet you return a non-const pointer to a member, thus allowing a violation of that promise.

In your class B, you make/break no promise since you don’t return a pointer to a member, you return a copy of it (and the member happens to be a pointer).