why am I getting errors with the Mammal.h class when compiling

Question

Guys, why am I getting errors here? The following was done in Visual C++

Mammal.h class file

#include <iostream>
using namespace std;

class Mammal
{
public:
    //constructor
    Mammal() { cout << "Mammal constructor...\n"; }
    Mammal(int age) { maAge = age; cout << "Mammal age constructor...\n"; }
    ~Mammal() { cout << "Mammal destructor...\n"; }
    //accessors
    void setMaAge(int age) { maAge = age; }
    void setMaWeight(int weight) { maWeight = weight; }
    int getMaAge() { return maAge; }
    int getMaWeight() { return maWeight; }
    //other func
    void speak() { cout << "Mammal Sound!...\n"; }
    void maSleep() { cout << "Mammal Sleeping!...\n"; }
protected:
    int maAge, maWeight;
};

Dog.h class file

#include <iostream>
#include "Mammal.h"
using namespace std;
enum BREED { golden, shepard, lab, doberman };
class Dog : public Mammal
{
public:
    //constructor
    Dog() { cout << "Constructing dog!...\n"; }
    Dog(int age) { Mammal(age); cout << "Constructing dog with age!...\n"; }
    Dog(int age, BREED breed) { Mammal(age); dogBreed = breed; 
    cout << "Constructing dog with age and breed!... \n"; }
    Dog(int age, int weight) { Mammal(age); maWeight = weight;
    cout << "Constructing dog with age and weight!...\n"; }
    ~Dog(){ cout << "Destruction of dog!...\n"; }
    //accessors
    void setDogAge(int age) { maAge = age; }
    void setDogWeight(int weight) { maWeight = weight; }
    void setDogBreed(BREED breed) { dogBreed = breed; }
    int getDogAge() { return maAge; }
    int getDogWeight() { return maWeight; }
    int getDogBreed() { return dogBreed; }
    //other func
    void dogWagTail() { cout << "Dog Wagging Tail!...\n"; }
    void dogBegFood() { cout << "Dos is Hungry!... Wants a bone.\n"; }
    void speak() { cout << "Dog Sound: Wof, Wof!\n"; }
private:
    BREED dogBreed;
};

main.cpp file

#include <iostream>
#include "Mammal.h"
#include "Dog.h"
using namespace std;

int main()
{
    Mammal fourLegs;//const mammal
    Dog Champ;//const dogs
    Dog Pimp(4, lab);
    Dog Mango(2, 54);
    fourLegs.speak();
    Champ.speak();
    Champ.setDogBreed(doberman);
    Pimp.setDogWeight(123);
    cout << "Pimp is: " << Pimp.getDogAge() << " years old - Weight: " << Pimp.getDogWeight() 
        << " pounds - breed: " << Pimp.getDogBreed() << endl;
    Mango.dogWagTail();
    system("pause");
    return 0;
}

errors:

1>------ Build started: Project: Overriding, Configuration: Debug Win32 ------
1>  main.cpp
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\mammal.h(5): error C2011: 'Mammal' : 'class' type redefinition
1>          c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\mammal.h(5) : see declaration of 'Mammal'
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(6): error C2504: 'Mammal' : base class undefined
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(10): error C2079: 'age' uses undefined class 'Mammal'
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(10): error C2082: redefinition of formal parameter 'age'
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(11): error C2079: 'age' uses undefined class 'Mammal'
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(11): error C2082: redefinition of formal parameter 'age'
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(13): error C2079: 'age' uses undefined class 'Mammal'
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(13): error C2082: redefinition of formal parameter 'age'
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(13): error C2065: 'maWeight' : undeclared identifier
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(17): error C2065: 'maAge' : undeclared identifier
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(18): error C2065: 'maWeight' : undeclared identifier
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(20): error C2065: 'maAge' : undeclared identifier
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\dog.h(21): error C2065: 'maWeight' : undeclared identifier
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\main.cpp(8): error C2079: 'fourLegs' uses undefined class 'Mammal'
1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\main.cpp(12): error C2228: left of '.speak' must have class/struct/union
1>          type is 'int'
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

any help appreciated

score 3 · Accepted Answer · edited Oct 29 '16 at 10:49

Read this:

1>c:\users\jorge\documents\visual studio 2010\projects\overriding\overriding\mammal.h(5): error C2011: 'Mammal' : 'class' type redefinition

Now, when your program compiles (starts from main.cpp) it includes iostream, then Mammal.h, then Dog.h.

When including Mammal.h and Dog.h program includes also all the includes from those files also.

So, Mammal.h is included first from main.cpp and then from Dog.h

To remove this error, simply use #ifndef, #define and #endif like this:

#ifndef _MAMMAL_H
#define _MAMMAL_H
#include <iostream>
using namespace std;

class Mammal
{
public:
    //constructor
    Mammal() { cout << "Mammal constructor...\n"; }
    Mammal(int age) { maAge = age; cout << "Mammal age constructor...\n"; }
    ~Mammal() { cout << "Mammal destructor...\n"; }
    //accessors
    void setMaAge(int age) { maAge = age; }
    void setMaWeight(int weight) { maWeight = weight; }
    int getMaAge() { return maAge; }
    int getMaWeight() { return maWeight; }
    //other func
    void speak() { cout << "Mammal Sound!...\n"; }
    void maSleep() { cout << "Mammal Sleeping!...\n"; }
protected:
    int maAge, maWeight;
};
#endif

Always include #ifndef #define AND #endif in all your .h files.

`_MAMMAL_H_` is a bad name for the include guard macro as it is an identifier reseverd for the implementation. It starts with an underscore followed by a capital letter. — CB Bailey, Dec 31 '10 at 09:21
read [Why I should not start an identifier with an underscore](http://stackoverflow.com/questions/228783/what-are-the-rules-about-using-an-underscore-in-a-c-identifier/228797#228797) — Martin York, Dec 31 '10 at 09:31
Also `#IFNDEF`, `#DEFINE` and `#ENDIF` aren't valid preprocessing directives; `#ifndef`, `#define` and `#endif` are. — CB Bailey, Dec 31 '10 at 09:35
Thanks guys, the guards took care of redefinition, and proper initialization of mammal object also needed correction... — miatech, Dec 31 '10 at 18:15

score 2 · Answer 2 · answered Dec 31 '10 at 09:10

2

Besides inclusion guards, in Dog object you are initializing Mammal object wrong way, you should initiliaze your base class like this;

Dog(int age) : Mammal(age) { ... }

answered Dec 31 '10 at 09:10

ismail

46,010
9
86
95

score 0 · Answer 3 · answered Dec 31 '10 at 09:04

You should be using include guards in your headers.

main.cpp is including Mammal.h before including Dog.h which itself includes Mammal.h. This means that the Mammal class is being redefined within main, hence the compiler errors. Include guards protect you from this.

score 0 · Answer 4 · answered Dec 31 '10 at 09:05

0

you should protect your headers

#ifndef _MAMMAL_H_
#define _MAMMAL_H_

class Mammal {
...
};

#endif



#ifndef _DOG_H_
#define _DOG_H_

class Dog {
...
};

#endif

answered Dec 31 '10 at 09:05

rlods

465
2
6

2

But don't invent names that start with an underscore. Neither for this purpose nor for any other. – Roland Illig Dec 31 '10 at 09:20
read [Why I should not start an identifier with an underscore](http://stackoverflow.com/questions/228783/what-are-the-rules-about-using-an-underscore-in-a-c-identifier/228797#228797) – Martin York Dec 31 '10 at 09:30

why am I getting errors with the Mammal.h class when compiling

Mammal.h class file

Dog.h class file

main.cpp file

errors:

4 Answers4