Working with multiple source file

Currently I'm following a tutorial on C++ All-in-One for Dummies @PG114 -> Dividing Between Source-Code Files. I'm trying to run a console program that are made up of 2 source file:

• main.cpp
• source2.cpp

The problem that I'm facing is whenever when I try to compile it, it will always show me an error message: " undefined reference to 'BigDog(int)". source2.cpp seems doesn't working.

I can assure that the code are error free as I copy and paste from the book. So what's the problem with it. I'm using Codeblock.

Did you forget about the header file?

This's what the book call me to do:
First code

Code:

---

#include <iostream>

using namespace std;

void BigDog(int KibbleCount);

int main(){
    BigDog(3);
    return 0;
}

---

Second code

Code:

---

#include <iostream>

using namespace std;

void BigDog(int KibblesCount){
        cout << "I'm a lucky Dog" << endl;
        cout << "I have " << KibbleCount << "pieces of food" << endl;
}

---

Do I need header? Even I try header on another tutorial it's even not working. Sorry if i don't provide a screenshot because my internet is too slow. Gonna wait till next month.

Oh, okay. In this case you don't need a header because you are directly forward declaring the BigDog function. This forward declaration would otherwise be placed in a header to be included.

Anyway, this means that the problem is that you compiled the source files separately without linking them to form the final executable program. Since you are using Code::Blocks for your IDE, it means that you probably did not add both source files to the same project.

Thank you. Found the solution. I didn't include them to debug and release. That's why. Thank you.

Hi. I just came another problem on another tutorial that involved a header. Why I'm getting error again even I copy exactly and I had linked the file properly.
Code 1

Code:

---

#include <iostream>

using namespace std;

string SafeCracker(int SafeID){
    return "Helllo" ;
}

---

Code 2

Code:

---

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

using namespace std;

int main()
{
    cout << "Surprise, surprise!" << endl;
    cout << "The combination is (once again)" << endl;
    cout << SafeCracker(12) << endl;

    return 0;
}

---

header:

Code:

---

using namespace std;

#ifndef SAFESTUFF_H_INCLUDED
#define SAFESTUFF_H_INCLUDED

string SafeCracker(int SafeID);

#endif // SAFESTUFF_H_INCLUDED

---

Error message that I got for header file: error: 'string' does not name a type

"using namespace" inside a header file is bad. And why is it specified before the header guard?!

Anyway, you need to #include <string> in both source files.

I tried #include <string or string.h> and it still not working. Anyway, this chapter isn't focus on "using namespace" and it's on Dividing Between Source-Code Files. So I think it's not very important. Later the book will clear up everything.

I tried the file that's created by the author and it work. I paste my code which i type recently into the author project , it work like charm. idk what's happen. I think maybe it's due to header setting. Something like that.

ok it's solved. Probably same problem like the recent one. Anyway thanks everyone.

Basically:

• In header files, do not use using declarations or using directives except within a restricted scope. Consequently, you would typically fully qualify names used in a header file.
• Include a header (or otherwise forward declare) if you are going to use a name.

Thus, your header should be like this:

Code:

---

#ifndef SAFESTUFF_H_INCLUDED
#define SAFESTUFF_H_INCLUDED

#include <string>

std::string SafeCracker(int SafeID);
 
#endif // SAFESTUFF_H_INCLUDED

---

Quote:

---

Originally Posted by ncode

ok it's solved. Probably same problem like the recent one. Anyway thanks everyone.

---

There is nothing that is as brutally honest as a compiler. I don't know about you, but I never dismiss typo. :p