c++ overloaded virtual function warning by clang?

Question

clang emits a warning when compiling the following code:

struct Base
{
    virtual void * get(char* e);
//    virtual void * get(char* e, int index);
};

struct Derived: public Base {
    virtual void * get(char* e, int index);
};

The warning is:

warning: 'Derived::get' hides overloaded virtual function [-Woverloaded-virtual]

(the said warning needs to be enabled of course).

I don't understand why. Note that uncommenting the same declaration in Base shuts the warning up. My understanding is that since the two get() functions have different signatures, there can be no hiding.

Is clang right? Why?

Note this is on MacOS X, running a recent version of Xcode.

clang --version
Apple LLVM version 5.0 (clang-500.1.74) (based on LLVM 3.3svn)

Update: same behavior with Xcode 4.6.3.

Answer 1

This warning is there to prevent accidental hiding of overloads when overriding is intended. Consider a slightly different example:

struct chart; // let's pretend this exists
struct Base
{
    virtual void* get(char* e);
};

struct Derived: public Base {
    virtual void* get(chart* e); // typo, we wanted to override the same function
};

As it is a warning, it doesn't necessarily mean it is a mistake, but it might indicate one. Usually such warnings have a means of shutting them off by being more explicit and letting the compiler know you did intend what you wrote. I believe in this case you can do the following:

struct Derived: public Base {
    using Base::get; // tell the compiler we want both the get from Base and ours
    virtual void * get(char* e, int index);
};