C++:error: redefinition of Class

Question

I 'm learning C++ class.

Here I write a struct call Day. Every function in it are checked careffully

#ifndef _Day_h
#define _Day_h_
typedef struct Day {
    int year;
    int month;
    int date;
    void print()const;
    Day (int y,int m,int d);
    Day ();
    Day(const Day& day);
    void setYear(int y);
    void setMonth(int m);
    void setDate(int d);
    int getYear()const;
    int getMonth()const;
    int getDate()const;
} Day;
#endif

Day.h

#include<cstdio>
#include"Day.h"
using namespace std;
Day::Day(int y,int m,int d){
    year = y;
    month = m;
    date = d;
    void print();

}
Day::Day(const Day& day){
    this->year=day.year;
    this->month=day.month;
    this->date=day.date;
}
void Day::print()const{
    printf("%4d-%2d-%2d",year,month,date);
}
void Day::setYear(int y){
    this->year = y;
}
void Day::setMonth(int m){
    this->month = m;
}void Day::setDate(int d){
    this->date = d;
}
int Day::getYear()const{
    return this->year;
}
int Day::getMonth()const{
    return this->month;
}
int Day::getDate()const{
    return this->date;
}

After my check, this should be no problem(maybe).

Then I write another class.

#ifndef _EMPLOYEE_H_
#include "Day.h"
#include <cstdio>
#include <iostream>
#include <string>
#include <typeinfo>
#define check_int(x) (typeid(x) != typeid(int) || ((x) <= 0))
#define check_str(s) (typeid((s)) != (typeid(std::string)))
#define NOH 10000
class Employee {
  private:
    int num;
    std::string name;
    bool sex; // true mean male false mean female
    Day birth;
    std::string job;

  public:
    Employee();
    Employee(int, std::string, bool, Day, std::string);
    void print()const;
    ~Employee();
};
#endif // !_EMPLOYEE_H_

Employee.h

#include"Employee.h"
#include "Day.h"
using namespace std;
Employee::Employee(int number, string nam, bool s, Day day1, string j): num(number), name(nam), sex(s), birth(day1), job(j) {}

void Employee::print() const {
    printf("编号: %d\n", this->num);
    cout << "姓名: " << this->name<<'\n';
    if (this->sex)
        printf("性别: 男\n");
    else
        printf("性别: 女\n");
    printf("生日: ");
    this->birth.print();
}

Employee.cpp

when I compile them with g++ Day.cpp Employee.cpp then comes to this

Employee.cpp:4:1: error: redefinition of ‘Employee::Employee(int, std::__cxx11::string, bool, Day, std::__cxx11::string)’
 Employee::Employee(int number, string nam, bool s, Day day1, string j): num(number), name(nam), sex(s), birth(day1), job(j) {}
 ^
Employee.h:42:1: note: ‘Employee::Employee(int, std::__cxx11::string, bool, Day, std::__cxx11::string)’ previously defined here
Employee.cpp:6:6: error: redefinition of ‘void Employee::print() const’
 void Employee::print() const {
      ^
Employee.h:65:6: note: ‘void Employee::print() const’ previously defined here

After reading many answer, It seem to be the problem of linking. But I can't find the redefinition after a long time checking.

Your header guards in `Employee.h` are not correct. I suggest you remove the header guards and replace them with `#pragma once` — Cory Kramer, Apr 12 '18 at 15:45
Unrelated to your problem, but not that symbols starting with an underscore and followed by an upper-case letter (like e.g. `_Day_h_`) is reserved in all scopes. See e.g. [this question and its answer](http://stackoverflow.com/questions/228783/what-are-the-rules-about-using-an-underscore-in-a-c-identifier) for details. — Some programmer dude, Apr 12 '18 at 15:47
I replace the `#ifndef ..... #define .... #endif` and replace them with `#pragma once` in Employee.h. Problem still exist. And I try to replace the `#ifndef _Day_h_.....` with `#pragma once` or `#ifndef _DAY_H_`. Then the struct in Day.h also redefinition when compiling.I don't sure if this is actually what you mean. Sorry, C is my first programing language. I still have a lot unknown thing to learn — yan liang, Apr 12 '18 at 16:33

score 1 · Answer 1 · answered Apr 12 '18 at 15:53

1

You forgot to complete the check for multiple inclusion of Employee.h. You file starts with:

#ifndef _EMPLOYEE_H_
#include "Day.h"

When it should really start with:

#ifndef _EMPLOYEE_H_
#define _EMPLOYEE_H_
#include "Day.h"

answered Apr 12 '18 at 15:53

tdk001

1,014
1
9
16

It does exist in my program, I miss it when I paste it here. The problem is still exist – yan liang Apr 12 '18 at 16:28

score 1 · Answer 2 · answered Apr 13 '18 at 04:51

1

Finally, I find my problem. After I corrected error in my code. I have a old .gch file in my directory. I compile after deleting the .gch file. Problem sloved. Thanks for everyone helped me.

answered Apr 13 '18 at 04:51

yan liang

65
5

score 0 · Answer 3 · answered Apr 12 '18 at 15:51

0

That is not full Employee header it say its defined on 65 line and you pasted only 25 lines.You have it defined probably in Employee header and employee.cpp

answered Apr 12 '18 at 15:51

MarkoShiva

83
1
2
10

This is where things get weird. My `Employee.h` has 25 lines. No more, I promise. And the compiler really saying it has 65 lines. I still can't not find redefinition after checking again and again. – yan liang Apr 12 '18 at 16:44
second line in your employee header should have ```#define _EMPLOYEE_H_``` – MarkoShiva Apr 12 '18 at 18:04
Also why defining day as struct and then use in new class? Isn't more normal to define Day as class and then use it when creating the employee class? – MarkoShiva Apr 12 '18 at 18:07
I have that line of code when I compile it. But I miss it when I paste my code here. It is for practices, I think it would be better to have the ability to write both class and struct. I don't think there's any syntax error it my struct. I will change it to class later when I have assess to a computer and see whether problem can be solved. – yan liang Apr 13 '18 at 00:07

C++:error: redefinition of Class

3 Answers3