class in header file gives undefined reference error

Asked May 06 '20 at 13:17

Active May 06 '20 at 13:17

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I am new in c++ and have a problem that I could not solve. I wrote a very simple class and put it in a header file. Below are the files:

point.h:

// point.h
#include <iostream>

#ifndef _POINT_H_
#define _POINT_H_
using namespace std;

class Point{
    private:
        double x;
        double y;
    public:
        void generate(double a, double b);
        void print();
};
#endif

point.cpp:

// point.cpp
#include <iostream>
#include "point.h"
using namespace std;

void Point::generate(double a, double b) {
    x = a;
    y = b;
} 

void Point::print() {
    cout << x << endl;
    cout << y << endl;
}

main.cpp:

// main.cpp
#include <iostream>
#include "point.h"
using namespace std;

int main() {
    Point A;
    A.generate(1,2);
    A.print();
    return 0; 
}

Every time I compile main.cpp I get the error:

main.cpp:(.text+0x30): undefined reference to `Point::generate(double, double)'
main.cpp:(.text+0x3c): undefined reference to `Point::print()'
[Error] ld returned 1 exit status

What have I done wrong? Hope for answers ;).

Greetings, Gerald

asked May 06 '20 at 13:17

Gerald

how you do compile (and link) ? – 463035818_is_not_an_ai May 06 '20 at 13:20
for compiling i use dev-c++. what do you mean by link? is it not sufficient just to compile and run the main.cpp? – Gerald May 06 '20 at 13:26
you have two translation units (aka .cpp) that are compiled seperately and need to be linked – 463035818_is_not_an_ai May 06 '20 at 13:27
how do i do that? – Gerald May 06 '20 at 13:29
i am reading a totorial ... and there the author does not mention anything about linking. – Gerald May 06 '20 at 13:30
Did you add `point.cpp` to your project? – Ted Lyngmo May 06 '20 at 13:35
you mean in main.cpp? – Gerald May 06 '20 at 13:38
like #include ? – Gerald May 06 '20 at 13:38
No, no. You shouldn't do that. Only include header files. The project you have in dev-c++ should contain two `.cpp` files. `main.cpp` and `point.cpp`. – Ted Lyngmo May 06 '20 at 13:42
yes it has. i included both in the project. – Gerald May 06 '20 at 13:44
Can you see the compilers command line or lines? It's probably `g++ ` or similar – Ted Lyngmo May 06 '20 at 13:45
now it worked. i put everything in a project and compiled and run the main.cpp and it seems to work. is it correct? – Gerald May 06 '20 at 13:47
It sounds correct - but wasn't that what you already had done? – Ted Lyngmo May 06 '20 at 13:49
well no. I did not put everything in a project. – Gerald May 06 '20 at 13:51
@Gerald Now I'm confused ... :-) – Ted Lyngmo May 07 '20 at 05:37

class in header file gives undefined reference error

0 Answers0