Calling a function from main function in cpp

Question

Indeed this question is asked and answered many times, but i could not make it correctly to call a function from the main program. I have three separate files as shown below.

//max.h 
int max(int num1, int num2);


//maxmain.cpp
#include <iostream>
#include "max.h"
using namespace std;

// function declaration
int max(int num1, int num2);

int main ()
{
   // local variable declaration:
   int a = 100;
   int b = 200;
   int ret;

   // calling a function to get max value.
   ret = max(a, b);

   cout << "Max value is : " << ret << endl;

   return 0;
}


//max.cpp
#include "max.h"
// function returning the max between two numbers
int max(int num1, int num2) 
{
   // local variable declaration
   int result;

   if (num1 > num2)
      result = num1;
   else
      result = num2;

   return result; 
}

When i compile maxmain.cpp , i get the error: maxmain.cpp:(.text+0x21): undefined reference to max(int, int) collect2: error: ld returned 1 exit status

Answer 1

Your code is fine as written. The issue is how you are compiling. You should list all of the cpp files in this case

g++ maxmain.cpp max.cpp -o maxmain