How do I successfully implement my .h file to my main .cpp file to make it run without errors

The code is supposed to take the class from the .h file and use it in the main to create a custom pet synopsis that can be stored later in another text file. I haven’t made the modular extraction to a text file yet because I need to get it at least working and able to actually compile and return the different arrays that make up the custom pet synopsis.

/usr/bin/ld: /tmp/: in function `__static_initialization_and_destruction_0(int, int)':
program3.cpp:(.text+0x411): undefined reference to `dog_list::dog_list()'
/usr/bin/ld: program3.cpp:(.text+0x426): undefined reference to `dog_list::~dog_list()'
collect2: error: ld returned 1 exit status

My .h file

#include<iostream>
#include<cstring>
#include<cctype>
#include<fstream>
using namespace std;
const int SIZE = 20;
const int END = 11;
class dog_list
{
    public:
    dog_list();
    ~dog_list();
    void record_pets();
    private:
    char name[SIZE];
    char breed[SIZE];
    char species[SIZE];
    char service[SIZE];
    char special[SIZE];
};
dog_list op;


void record_pets();

my main .cpp file

#include "program3.h"
int main()
{
       op.record_pets();
        return 0;

}


void dog_list::record_pets()
{
    char personal_list[SIZE];
    int i = 0;
    char again;

    do
    {

        cout << "Enter in pets name: ";
        cin.get(op.name,25,'\n');
        cin.ignore(100,'\n');   
        cout << endl << "Enter breed of pet:  ";
        cin.get(op.breed, 25, '\n');
        cin.ignore(100,'\n');
        cout << endl << "Enter species: ";
        cin.get(op.species,25,'\n');
        cin.ignore(100,'\n');
        cout << endl <<  "Enter in service qualifications: ";
        cin.get(op.service,25,'\n');
        cin.ignore(100,'\n');
        cout << endl << "Enter in special notes: ";
        cin.get(op.special,25,'\n');
        cin.ignore(100,'\n');
        cout << endl;

        cout << "Name:  " << op.name << endl;
        cout <<"Breed: " <<  op.breed << endl;
        cout << "Species: " << op.species << endl;
        cout << "Service Qualifications: " << op.service << endl;
        cout << "Special Notes: " << op.special << endl;

        cout << "Pet saved! Would you like to enter another pet? Y/N: " << endl;
        cin >> again;
        cin.ignore(100,'\n');
        cout << endl;

        if(again == 'y')
        {
            again = toupper(again);
        }


    }while(again == 'Y' && i <= END);
    {
        ++i;    
    }   
}

>Solution :

You never implement the constructor and destructor, you just declare it:

dog_list();
~dog_list();

You have to implement it, for example, in main.cpp:

dog_list::dog_list() = default;
dog_list::~dog_list() = default;