=== [[C++]] [[OOP]]===

  /** @author: http://www.rzr.online.fr
    * How comes typed function overloading break it all ? */

  #include <iostream>
  using namespace std;

  #define CONFLICT // choose one of these not CONFLICT + OVERLOAD
  #define OVERLOAD

  class Base {
  public:
  virtual void main() { fvirtual();  } // show polymorphism

  virtual void fvirtual( std::ostream &  out = std::cout )
  { out<<"Base::fvirtual"<<endl; } // method to be linked dynamicly

  virtual void fvirtual(char* &arg, std::ostream &  out = std::cout )
  { out<<"Base::fvirtual "<< arg <<endl; } // will conflict with derived one

  };

  class Derived : public Base {
  public:
  #ifdef CONFLICT
  virtual void fvirtual(std::ostream &  out = std::cout )
  { out<<"Derived::fvirtual"<<endl; } // will conflict with base one
  #endif

  };

  int main(int argc, char* argv[[]]) {
  Derived cd;  cd.main(); // will illustrate what is polymorphism

  //cd.fvirtual( "test" , std::cout);

  #ifdef OVERLOAD
  Derived* c = new Derived;
  /*
    In function `int main(int, char**)':
    error: no matching function for call to `
    Derived::fvirtual(char*&, std::ostream&)'
    error: candidates are: virtual void
    Derived::fvirtual(std::ostream&)
    */
  #else
  Base* c = new Derived;
  /*
    will print
    Base::fvirtual ./cpppolymorphismdefaultparm
    */
  #endif
  c->main(); // ok it is allways linked
  c->fvirtual( argv[[0]] , std::cout); // will cause an error on compilation

  return 0;
  }


  /*
  TARGET=cpppolymorphismdefaultparm
  CXXFLAGS="-g -Wall -DMAIN_${TARGET}"
  make ${TARGET} CXXFLAGS="${CXXFLAGS}"  \
  &&  ${TARGET} || gdb ${TARGET}
  */

irc://irc.freenode.net/#c++ helped :

  <calvin_> RzR: function lookup and overload resolution are two distinct steps, performed in sequence. in short, the fvirtual(char*... ) becomes hidden in Derived.
  <RzR> just because it has the same name ?
  <RzR> thats annoying
  <PlasmaHH> yes, having the same name is called overloading....
  <ryg> hiding rule
  <ryg> when you override one overloaded version, you'll have to override them all.
  <RzR> the mangled name is different , isnt it ?
  <RzR> i thought that parameters where also defining a method
  <PlasmaHH> c++ has no concept of mangling names, only the implementations have...
  <RzR> ok well it makes sense now
  <RzR> so it is tricky to use generic names for functions

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