Question

This is a tutorial I’ve been following and I’ve done everything that it tells but it doesn’t work. I have three files: the main.cpp, burrito.h (the class), and burrito.cpp.

And here are the three files respectively.

main.cpp

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

int main() {

    Burrito bo;

    return 0;
}

Burrito.h

#ifndef BURRITO_H
#define BURRITO_H


class Burrito {
    public:
        Burrito();
};

#endif // BURRITO_H

Burrito.cpp

#include <iostream>
#include "Burrito.h"

using namespace std;

Burrito::Burrito() {
    cout << "Hello World" << endl;
}

When I build and run I get the following error:

...undefined reference to `Burrito::Burrito()'
collect2: ld returned 1 exit status
Process terminated with status 1 (0 minutes, 6 seconds)
1 errors, 0 warnings

I’m compiling using CodeBlocks.

Answer 1

I’m using CodeBlocks

This is the issue.

If you’re starting to learn C++ it’s (unfortunately) essential to learn about translation units. An IDE like Code::Blocks hides this detail from you – and does it wrong, in this case (this isn’t really the fault of Code::Blocks though, it can’t automatically guess what to do in this case without configuation).

In the beginning, drop the IDE, go to the command line for compiling. Compile the two translation units separately and link them together explicitly.

g++ -o burrito.o burrito.cpp
g++ -o main.o main.cpp
g++ -o main main.o burrito.o

Every good beginners’ C++ book will explain how this works.