"undefined reference to" error while using global variables in VS code

Question

I am learning C++ using Bjarne's book, everything was fine until I get to learn how to include header files.

My codes are as below:

my.h

#ifndef MY_H
#define MY_H

extern int foo;
void print_foo();

#endif

my.cpp

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

using namespace std;

void print_foo() {
    cout << foo << endl;
}

use.cpp

#include "my.h" 

int foo = 7;

int main() {
    print_foo();
}

I put them under the same folder with no space in folder name, I opened a new window from VS code, then I ran user.cpp and get the error saying undefined reference to print_foo.

Did I miss some key steps using VS code? because I think the codes are correct.

I haven't received any error after code build. Code is building and running fine. You need to build whole project and not single user.cpp file. — Sumeet, May 06 '19 at 05:27
Looks good to me. Make certain that my.cpp is being compiled by putting in some garbage that can't possibly compile, like a line of aaaaaaaaaaaaaaaaaaaa, and seeing if you get an error message about the aaaaaaaaaaaaaaaaaaas. — user4581301, May 06 '19 at 05:29
you should build **both** cpps not only one. add to a project and build the project. — SHR, May 06 '19 at 05:30
may I ask how to build a project in VS code, some source online says open a new window is equivalent — n33, May 06 '19 at 05:39

score 2 · Answer 1 · edited May 06 '19 at 14:54

2

g++ my.cpp use.cpp -o main

use this in the terminal

edited May 06 '19 at 14:54

user4581301

33,082
7
33
54

answered May 06 '19 at 05:30

rencedm112

397
3
11

this gives errors: g++.exe: error: main: No such file o64-r directory -w6 g++.exe: error: unrecognized commandb64 line option '-0' – n33 May 06 '19 at 05:36
Should be `-o` not `-0` – Alan Birtles May 06 '19 at 06:47

"undefined reference to" error while using global variables in VS code

1 Answers1