What can a ‘const’ method change? Without explicitly casting away constness, a const member function can change: mutable data members, and any data the class has non-const access to, irrespective of whether that data’s accessible: via member variables that are pointers or references, via pointers or references passed as function arguments, via pointers or references … Read more
When you apply the const qualifier to a nonstatic member function, it affects the this pointer. For a const-qualified member function of class C, the this pointer is of type C const*, whereas for a member function that is not const-qualified, the this pointer is of type C*. A static member function does not have … Read more
When you call a.foo();, the compiler goes through overload resolution to find the best function to use. When it builds the overload set it finds void foo() const and void foo() Now, since a is not const, the non-const version is the best match, so the compiler picks void foo(). Then the access restrictions are … Read more