C++ how to fix the error Undefined reference to function?

Question

My code is raising this error:

supportCrew.cpp:(.text+0x15): undefined reference to `sportsPsychologist::sportsPsychologist()'
supportCrew.cpp:(.text+0x25): undefined reference to `Physiotherapist::Physiotherapist()'
supportCrew.cpp:(.text+0x35): undefined reference to `trainer::trainer()'
supportCrew.cpp:(.text+0x47): undefined reference to `trainer::trainer()'

The two relevent classes/cpp files are supportCrew and Person

Person.cpp

#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <chrono>
#include <random>
#include <algorithm>

Person::Person(std::string pName, int pAge, int pExperience) {
    name = pName;
    age = pAge;
    experience = pExperience; //years of experience
};
   

Athlete::Athlete(std::string name, int age, int experience, std::string gender, double height, double weight)
{
    gender = gender;
    height = height;
    weight = weight;
};

Physiotherapist::Physiotherapist(std::string name, int age, int experience, int recovery, int readiness) {
    readinessScore = readiness;
    recoveryScore = recovery;
};

sportsPsychologist::sportsPsychologist(std::string name, int age, int experience, int pressure, int injury, int successFail) {

pressurescore = pressure;
injuryscore = injury;
successfailscore = successFail;

};

trainer::trainer(std::string name, int age, int experience,std::string specialization, int performance, int consistency) {

specialization = specialization;
performanceScore = performance;
consistencyScore = consistency;

};

Person.h

#ifndef PERSON
#define PERSON

class Person {

std::string name;
int experience; //in years
int age;

public:
Person(std::string pName, int pAge, int pExperience);
Person();

virtual ~Person(){};
std::string getName() {return randomName();};
int getAge(){return randomAge();};
int getExperience(){return randomExperience();};
void printData(std::string, int, int);

std::string randomName();
int randomAge();
int randomExperience();

};

class Athlete: public Person{

private: 
std::string gender;
double height;
double weight;

public:
Athlete(std::string pName, int pAge, int pExperience, std::string gender, double height, double weight);
Athlete();
virtual ~Athlete(){};
std::string &getGender(){return gender;};
std:: string randomGender();
double randomHeight();
double randomWeight();
};


class Physiotherapist: public Person{
private:
    int recoveryScore;
    int readinessScore;

public:
Physiotherapist(std::string pName, int pAge, int pExperience, int recoveryScore, int readinessScore); 
Physiotherapist();
int &getscoreRecovery(){return recoveryScore;};
int &getscoreReadiness(){return readinessScore;};
};

class sportsPsychologist: public Person {
private:
    int pressurescore;
    int injuryscore;
    int successfailscore;

public: 
sportsPsychologist(std::string pName, int pAge, int pExperience, int pressureScore, int injuryScore, int successfailScore); 
sportsPsychologist();
int &getscorePressure(){return pressurescore;};
int &getscoreInjury(){return injuryscore;};
int &getscoreSuccues_Fail(){return successfailscore;};    
};

class teamManager: public Person {

public:
teamManager(std::string pName, int pAge, int pExperience); 
teamManager(); 

};

class trainer: public Person {
private:
    std::string specialization; 
    int performanceScore;
    int consistencyScore;

public: 
trainer(std::string pName, int pAge, int pExperience, std::string specialization, int performanceScore, int cocsistencyScore);
trainer();
std::string &getSpecialization(){return specialization;};
int &getscorePeformance(){return performanceScore;};
int &getscoreConsistency(){return consistencyScore;};
};


#endif 

supportCrew.h

#ifndef SUPPORTCREW
#define SUPPORTCREW
#include "Person.h"

class supportCrew {

private:
sportsPsychologist Psychologist;
Physiotherapist physio;
trainer trainer1;
trainer trainer2;

public:
supportCrew(sportsPsychologist,Physiotherapist,trainer,trainer);
supportCrew();
};
#endif

supportCrew.cpp

#include <iostream>
#include <sstream> 
#include <fstream>

#include "compDay.h"
#include "Competion.h"
#include "Events.h"
#include "Location.h"
#include "Octathlon.h"
#include "Person.h"
#include "supportCrew.h"
#include "theTeam.h"
#include "weatherSystem.h"

supportCrew::supportCrew() {
}

Answer 1

It seem the skill you are missing is how to call base class constructors. So

Physiotherapist::Physiotherapist(std::string name, int age, int experience, int recovery, int readiness) {
    readinessScore = readiness;
    recoveryScore = recovery;
};

should really be

Physiotherapist::Physiotherapist(std::string name, int age, int experience, int recovery, int readiness)
    : Person(name, age, experience) {
    readinessScore = readiness;
    recoveryScore = recovery;
}

If you do that then the Person::Person() constructor isn't required because you are explicitly calling the Person::Person(std::string pName, int pAge, int pExperience); constructor.

Of course you should be using initialization lists everywhere. So the above code is even better written like this

Physiotherapist::Physiotherapist(std::string name, int age, int experience, int recovery, int readiness) 
     : Person(name, age, experience)
     , readinessScore(readiness)
     , recoveryScore(recovery) {
}

If you don't call the base class construcor from an initialization list, then the default base class constructor will be called implicitly. I guess this is why you've decalred all these default constructors. But if you code it like I show you above then you (probably) don't need all these default constructors.