Using a header file, initialization file, and main file for structs in C++

Question

I am having difficulty executing a program that I wrote with structs. My program has a header file, an initialization file, and a main file. When I compiled it, the compiler complained and later I found out that I forward declared my struct name as Company but initialized it using company so I changed it to Company but still the compiler complains after I did this. How can I fix this? Any help will be greatly appreciated. Below is my code for my three files:

structs.h:

#ifndef STRUCTS_H
#define STRUCTS_H

struct Company{
  double salary;
  int workers;
  int bosses;
}

#endif

initialization.cpp:

Company a = {1200340.99, 30000, 3};
Company b = {500320.85, 5000, 2};

main.cpp:

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

void PrintInfo(Company company){
  using namespace std;
  cout << "salary: " << Company.salary << endl;
  cout << "workers: " << Company.workers << endl;
  cout << "bosses: " << Company.bosses << endl;
}

int main(){
  PrintInfo(a);
  PrintInfo(b);
  return 0;
}

Note that 'forward declared' means something different. There's no forward declaration in this code just regular declaration. — john
– john, Commented Dec 6, 2013 at 13:38
please make sure you show the exact error messages when writing your questions. — crashmstr
– crashmstr, Commented Dec 6, 2013 at 13:51

Felix Glas · Accepted Answer · 2013-12-06 14:02:45Z

4

You need a ; after the definition of struct Company

In PrintInfo you need to reference the object company (lowercase c) and not the class Company (uppercase C), e.g.

cout << "salary: " << company.salary << endl;   // lowercase c
cout << "workers: " << company.workers << endl; // lowercase c
cout << "bosses: " << company.bosses << endl;   // lowercase c

As a and b is initialized (globally) in a different source file you must redeclare them with external linkage in the source file that need to access them using the extern keyword, e.g.

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

extern Company a;
extern Company b;

/* ... */

Consider initializing a and b where they are used instead:

int main() {
    Company a = {1200340.99, 30000, 3}; // Init here.
    Company b = {500320.85, 5000, 2};   // Init here.

    PrintInfo(a);
    PrintInfo(b);
    // return 0; // Unnecessary in main function.
}

In function PrintInfo, as you are not modifying the argument you should pass the class Company as reference to const to avoid copying, i.e. declare the function using this:
```
void PrintInfo(const Company& company)
```

edited Dec 6, 2013 at 14:02

answered Dec 6, 2013 at 13:42

Felix Glas

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1 Comment

πάντα ῥεῖ Over a year ago

Also some extern is missing for a and b in the OP's sample.

double_g · Accepted Answer · 2013-12-06 14:36:35Z

2

A structure requires a ';' at the end

struct Company{
  double salary;
  int workers;
  int bosses;
};

edited Dec 6, 2013 at 14:36

answered Dec 6, 2013 at 13:37

double_g

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Comments

crashmstr · Accepted Answer · 2013-12-06 13:50:43Z

0

In addition to the other answers, the code in main.cpp knows nothing about a and b in your initialization.cpp.

You need to either add an extern declaration in structs.h or move those into main.cpp.

But, you should also consider not making them global variables, like this:

int main()
{
    Company a = {1200340.99, 30000, 3};
    Company b = {500320.85, 5000, 2};
    PrintInfo(a);
    PrintInfo(b);
    return 0;
}

answered Dec 6, 2013 at 13:50

crashmstr

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