How to handle and avoid Recursions - c++

Question

I'm using custom classes to manage a vending machine. I can't figure out why it keeps throwing a stack overflow error. There are two versions to my program, the first is a basic test to see whether the classes etc work, by pre-defining certain variables. The second version is what it should be like, where the variables in question can change each time the program is ran (depending on user input).
If anyone can suggest ways of avoiding this recursion, or stack overflow, I'd great. Below is the code for the three classes involved;
class Filling
{
protected:
vector<Filling*> selection;
string fillingChosen;
public:
virtual float cost()
{
return 0;
}
virtual ~Filling(void)
{
//needs to be virtual in order to ensure Condiment destructor is called via Beverage pointer
}
};
class CondimentDecorator : public Filling
{
public:
Filling* filling;
void addToPancake(Filling* customerFilling)
{
filling = customerFilling;
}
~CondimentDecorator(void)
{
delete filling;
}
};
class Frosted : public CondimentDecorator
{
float cost()
{ //ERROR IS HERE//
return (.3 + filling->cost());
}
};
Below is the code used to call the above 'cost' function;
void displayCost(Filling* selectedFilling)
{
cout << selectedFilling->cost() << endl;
}
Below is part of the code that initiates it all (main method);
Filling* currentPancake = NULL;
bool invalid = true;
do
{
int selection = makeSelectionScreen(money, currentStock, thisState);
invalid = false;
if (selection == 1)
{
currentPancake = new ChocolateFilling;
}
else if...
.
.
.
.
else
invalid = true;
} while (invalid);
bool makingSelection = true;
CondimentDecorator* currentCondiment = NULL;
do
{
int coatingSelection = makeCoatingSelectionScreen(money, currentStock, thisState);
if (coatingSelection == 1)
currentCondiment = new Frosted;
else if (coatingSelection == 2)...
.
.
.
else if (coatingSelection == 0)
makingSelection = false;
currentCondiment = thisSelection;
currentCondiment->addToPancake(currentPancake);
currentPancake = currentCondiment;
displayCost(currentPancake);
//Below is the code that DOES work, however it is merely meant to be a test. The
//above code is what is needed to work, however keeps causing stack overflows
//and I'm uncertain as to why one version works fine and the other doesn't
/*currentCondiment = new Frosted;
currentCondiment->addToPancake(currentPancake);
currentPancake = currentCondiment;
displayCost(currentPancake);
currentCondiment = new Wildlicious;
currentCondiment->addToPancake(currentPancake);
currentPancake = currentCondiment;
displayCost(currentPancake);*/
} while (makingSelection);
displayCost(currentPancake);
delete currentPancake;

Answer 1

The infinite recursion happens when you call displayCostwith a Frosted whose filling is a Frosted as well. And that happens right here:
currentCondiment->addToPancake(currentPancake);
currentPancake = currentCondiment;
displayCost(currentPancake);
You set the filling of currentCondiment to currentPancake, then call displayCost with currentCondiment.
In the process you also leak the memory that was originally assigned to currentPancake.
Btw currentCondiment = thisSelection; also leaks memory.
Idea: Use smart pointers like std::unique_ptr to get rid of the leaks.