C++ function overloading, name mangling, name hiding are somehow related to the same issue: overload resolution at compile time ( note override is run-time resolution).
What is C++ Function overloading:
two or more functions have same name and but have different parameters/signature.
The way compiler distinguishes those different functions is adding additional information about arguments to function names called Name Mangling. The extern “C” in C++ is to make sure the function names are unmangled, thus being able to be called in C style.
Overloading with inheritance
The function overloading become interesting in the case of c++ inheritance
class Base { public: virtual void f() {}; }
class Derived: public Base { public: void f(int){}; }
int main(){ Derived c; c.f(); return 0 }
if we call Derived.f(), the compiler will fail. why?
In C++, phases of the function call process are as following
- Name lookup
- Overload resolution
- Access control
Once a name f(int) was found in the name lookup phrase in the Derived class, the compiler will move to the overload resolution phrase: now the C++ name hiding rule will hide all the same name functions ( even it is a virtual function) in Base class, which means Derived.f() is invisible, though Derived.Base::f() is still visible. So there is no f() in this scope, the compile will fail.
why do we need C++ name hiding rule?
One reason is due to fragile base class problem described in http://thesyntacticsugar.blogspot.com/2011/10/behind-scenes-name-hiding-in-c.html
This is just one reason, but NOT a strong reason, as Java overloading works across scopes contrary to C++. please see example from:
http://www.geeksforgeeks.org/does-overloading-work-with-inheritance/
Can someone tell me why Java work this way?
The work-around for name hiding
one is using directive
class Derived: public Base {
public:
using Base:f;
void f(int);
}
References:
http://www.programmerinterview.com/index.php/c-cplusplus/c-name-hiding/
http://thesyntacticsugar.blogspot.com/2011/10/behind-scenes-name-hiding-in-c.html
