C++ very simple unresolved external

Question

I have an unresolved external in Visual Studio C++ compiler that's driving me absolutely crackers. The class header and source files are extremely simple.

Header file:

// Header file: Rational.h
class Rational
{
public:
    Rational ( int = 0, int = 1 ); 
private:
    int numerator;
    int denominator;    
};

Source file:

// Source file: Rational.cpp
#include <iostream>
#include "Rational.h"

using namespace std;

Rational::Rational( int n, int d )
{
    numerator = n;
    denominator = d;
}

The error messages are:

error LNK2019: unresolved external symbol _main referenced in function    ___tmainCRTStartup    

error LNK1120: 1 unresolved externals

How is this possible? I must be missing something very fundamental here but now I am at the end of my tether.

I have looked at other questions on this topic but can't find an answer.

You forgot to define the entry point... create a new file and add int main(int argc, char **argv) — Ed Swangren
– Ed Swangren, Commented Jan 5, 2014 at 21:40
Apologies all I didn't realise I needed main. This is fixed now. Thanks, and apologies for the silly question. — OliKlima
– OliKlima, Commented Jan 5, 2014 at 21:43

Lightness Races in Orbit · Accepted Answer · 2014-01-05 21:56:33Z

4

Have you got a main()? – Alan Stokes
@ Alan. Not yet. – OliKlima

Well, there you go then.

It's the main that's not being found, as the error message pretty much states.

answered Jan 5, 2014 at 21:56

Lightness Races in Orbit

387k77 gold badges670 silver badges1.1k bronze badges

Sign up to request clarification or add additional context in comments.

Comments

user1508519 · Accepted Answer · 2014-01-05 22:02:29Z

1

If you're trying to link Rational.cpp into an executable, it needs an entry point (main). If you're simply creating an object file, then there is no linking done. Your entry point can be placed in another file, i.e main.cpp, and then link it together.

First, put this in main.cpp:

int main()
{
}

Then run the following commands:

g++ -c Rational.cpp
g++ -c main.cpp
g++ -o main main.o rational.o

answered Jan 5, 2014 at 22:02

user1508519

1 Comment

OliKlima Over a year ago

Thanks, I won't be making that mistake again :)

Collectives™ on Stack Overflow

C++ very simple unresolved external

2 Answers 2

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related