Why won't this code run? I am confused

Question

// main.cpp
#include <iostream>
#include "add.h"

int main(){
  std::cout << "Hello World\n";
  std::cout << add(3,4) << std::endl;
  return 0;
}

// add.h
#ifndef add_h
#define add_h

int add(int x, int y);

#endif /* add_h */

// add.cpp
#include "add.h"

int add(int x, int y){
  return x + y;
}

I am compiling with 'g++ -std=c++11 main.cpp -o main'. I keep getting linker errors. I copied it exactly from a tutorial too.

Welcome to Stack Overflow. Please take the time to read [The Tour](http://stackoverflow.com/tour) and refer to the material from the [Help Center](http://stackoverflow.com/help/asking) what and how you can ask here. — πάντα ῥεῖ, Jun 14 '17 at 00:47

score 1 · Answer 1 · edited Jun 14 '17 at 02:16

1

Right now the add.cpp file is not properly linked.

What you need to do:

Create an add.o file by
```
g++ -c add.cpp -o add.o
```
Link the .o file to compile
```
g++ -std=c++11 add.o main.cpp -o main
```

edited Jun 14 '17 at 02:16

Pang

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answered Jun 14 '17 at 00:42

James Maa

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1

Or you can simply add add.cpp by g++ -std=c++11 main.cpp add.cpp -o main – James Maa Jun 14 '17 at 00:43
THANK YOU! Also what does the -c flag mean? – Ron B Jun 14 '17 at 00:47
@RonB It means that the linker should just create an object file rather than trying to create an executable. – πάντα ῥεῖ Jun 14 '17 at 00:49
1

@JamesMaa I'd pop that comment into the answer. It will be more useful than the existing answer for most future askers of this question. – user4581301 Jun 14 '17 at 00:59

Why won't this code run? I am confused

1 Answers1