Builder design pattern does not work for me - c++

Question

I have a problem with a c++ code I just written. The code is a sample of the Builder design pattern. I created an abstract builder class, and two classes inherited from this class: MonsterBuilder and RuffianBuilder. I created a Builder class, this class receives a Monster or a RuffianBuilder, and constructs a new instance of these classes. The problem comes here: if the MonsterBuilder class is used to build a new instance the program terminates with an error (a.exe has stopped working). If the Builder receives a RuffianBuilder, it constructs a new instance without an error. Here is the sample code:
#include <iostream>
class Character
{
private:
// Attributes
int dex;
int str;
int end;
// skills
int lockpick;
int guns;
int sneak;
/***************************************** Setters ********************************************************/
// Attribute setters
public:
void setStrength(const int &s)
{
this->str = s;
}
void setDexterity(const int &d)
{
this->dex = d;
}
void setEndurance(const int &e)
{
this->str = e;
}
// Skill setters
void setLockpick(const int &s)
{
this->lockpick = s;
}
void setSneak(const int &s)
{
this->sneak = s;
}
void setGuns(const int &s)
{
this->guns = s;
}
int getGuns()
{
return this->guns;
}
int getStrength()
{
return this->str;
}
};
/* Abstract builder */
class CharacterBuilder
{
protected:
Character * int_character;
public:
Character * getCharacter()
{
return int_character;
}
void buildCharacter()
{
int_character = new Character;
}
virtual void buildSkills() = 0;
virtual void buildAttributes() = 0;
};
class MonsterBuilder : public CharacterBuilder
{
public:
virtual void buildSkills()
{
int_character->setLockpick(10);
int_character->setSneak(12);
int_character->setGuns(50);
}
virtual void buildAttributes()
{
int_character->setStrength(5);
int_character->setDexterity(5);
int_character->setEndurance(5);
}
};
class RuffianBuilder : public CharacterBuilder
{
public:
virtual void buildSkills()
{
int_character->setLockpick(10);
int_character->setSneak(12);
int_character->setGuns(50);
}
virtual void buildAttributes()
{
int_character->setStrength(5);
int_character->setDexterity(5);
int_character->setEndurance(5);
}
};
class Builder
{
public:
void setBuilder(CharacterBuilder * builder)
{
this->builder = builder;
}
Character * getCharacter()
{
return builder->getCharacter();
}
void buildCharacter()
{
//std::cout << builder->buildSkills;
builder->buildSkills();
builder->buildAttributes();
}
private:
CharacterBuilder * builder;
};
int main()
{
Builder B;
RuffianBuilder R;
MonsterBuilder Mo;
B.setBuilder(&R);
B.buildCharacter();
std::cout << B.getCharacter()->getGuns();
std::cout << B.getCharacter()->getStrength();
B.setBuilder(&Mo);
B.buildCharacter();
//std::cout << B.getCharacter()->getStrength();
return 0;
}
What causes this problem? Could somebody explain it?

Answer 1

Reading uninitlalized variable will cause undefined behavior.
I added builder->buildCharacter(); to Builder::buildCharacter() and then this code seems working well.
class Builder
{
public:
void setBuilder(CharacterBuilder * builder)
{
this->builder = builder;
}
Character * getCharacter()
{
return builder->getCharacter();
}
void buildCharacter()
{
//std::cout << builder->buildSkills;
builder->buildCharacter(); // add this line
builder->buildSkills();
builder->buildAttributes();
}
private:
CharacterBuilder * builder;
};