class - C++ classes, segmentation fault when calling member function -

i learning c++ , have been experimenting classes head around how work. have programmed classes in java before now.

in code have class definition , driver test. in comments have mention works , doesn't. want know why instantiating objects 1 way works in other ways errors. compiler, make file, or class code? constructor/default constructor? when compare code others textbook, can't see i've gone wrong.

using: code::blocks 10.5 on linux mint 13.

header file:

#ifndef enemy_h #define enemy_h #include <string> using namespace std;  class enemy { public:     enemy();     enemy(int, int, string);      ~enemy();      string display();      // setter , getters:     int gethp();     void sethp(int);     int getx();     void setx(int);     int gety();     void sety(int);     string getname();     void setname(string);  private:     int hitpoints;     int x_pos;     int y_pos;     string name; }; #endif // enemy_h 

member function defifnitions:

#include "enemy.h" #include <iostream> #include <string>   // default ctor  enemy::enemy() {     cout << "creating enemy default ctor.\n"; }  //ctor enemy::enemy(int x, int y, string str) {     cout << "creating object  name: " << str << endl;     setx(x);     sety(y);     sethp(100);     setname(str); }  //dtor enemy::~enemy() {     cout << "destroying enemy: " << name << endl; }  string enemy::display() {     cout<<name<<" -  x: "<<x_pos<<", y: "<<y_pos<<", hp: "<<hitpoints<<endl; }  int enemy::gethp(){     return hitpoints; } void enemy::sethp(int hp){    hitpoints = hp; } int enemy::getx(){     return x_pos; } void enemy::setx(int x){     x_pos = x; } int enemy::gety(){     return y_pos; } void enemy::sety(int y){     y_pos = y; } string enemy::getname(){     return name; } void enemy::setname(string objectname){     name = objectname; } // end of function definitions 

driver:

#include "enemy.h" #include <iostream> #include <string>  using namespace std;  int main() {     cout << "program started.\n" << endl;      // initialise few enemy objects     enemy e1(1, 1, "e1");     enemy e2(2, -4, "e2");     enemy e3;     enemy e4;     enemy *e5 = new enemy(4, 5, "e5");       e1.display(); // <- success!     e2.display(); // <- success!     e3.display(); // <- segmentation fault @ run time     e4.display(); // <- segmentation fault @ run time     e5.display(); // <- compile time error "request member                   //    'display'" in 'e5'. of                   //    non-class type 'enemy'      cout << "end of program.\n";     return 0; } 

what's causing segfault fact you're flowing off edge of function that's supposed return string (which undefined behavior):

string enemy::display() //^^^^ you're supposed return string {     cout<<name<<" -  x: "<<x_pos<<", y: "<<y_pos<<", hp: "<<hitpoints<<endl;     // no return statement } 

the rest in @chris' answer.