Duplicate code using c++11

Something like that will do nicely:

template<bool bonus = false>
void MyFunction()
{
  foo();
  bar();
  if (bonus) { doBonusStuff(); }
  foobar();
}

Call it via:

MyFunction<true>();
MyFunction<false>();
MyFunction(); // Call myFunction with the false template by default

The “ugly” template can be all avoided by adding some nice wrappers to the functions:

void MyFunctionAlone() { MyFunction<false>(); }
void MyFunctionBonus() { MyFunction<true>(); }

You can find some nice informations on that technique there. That is an “old” paper, but the technique in itself stay totally right.

Provided you have access to a nice C++17 compiler you can even push further the technique, by using the constexpr if, like that:

template <int bonus>
auto MyFunction() {
  foo();
  bar();
  if      constexpr (bonus == 0) { doBonusStuff1(); }
  else if constexpr (bonus == 1) { doBonusStuff2(); }
  else if constexpr (bonus == 2) { doBonusStuff3(); }
  else if constexpr (bonus == 3) { doBonusStuff4(); }
  // Guarantee that this function will not compile
  // if a bonus different than 0,1,2,3 is passer
  else { static_assert(false);}, 
  foorbar();
}