Error with compiling simple C++ application

Question

I have a pretty syntax-correct and very simple app that takes two integers from user and do substraction and addition of them. But when i try to compile a program, i'm getting this error:

Could not find 'C:\Users\MyUsername\source\repos\SimpleCalculator\SimpleCalculator\Debug\SimpleCalculator.obj'. SimpleCalculator.exe was built with /DEBUG:FASTLINK which requires object files for debugging.

Here is my code:

#include "stdafx.h"
#include <iostream>
using namespace std;

void main()
{
int a, b;
cout << "Welcome." << endl;

cout << "Enter first number: ";
cin >> a;
cout << "Enter second number: ";
cin >> b;

cout << "A+B is: ";
cout << addition(a,b) << endl;

cout << "A-B is: ";
cout << substraction(a,b) << endl;

system("pause");

}

int addition(int a, int b) {
    return a + b;
}

int substraction(int a, int b) {
    return a - b;
}

This error only happens when i have functions. When my code is like:

cout << "A+B is: ";
cout << a+b << endl;

there is no errors.

Imagine you are the compiler, you can judge code as valid only with what you have read so far from the top. Everything at the bottom is unknown to you. Now you come to `addition(a,b)`. How are you to know what `addition` is? — StoryTeller - Unslander Monica, Sep 11 '17 at 12:14
@ishpreet Not in cpp : https://stackoverflow.com/questions/204476/what-should-main-return-in-c-and-c — rndus2r, Sep 11 '17 at 12:18
@ishpreet - Only if your compiler and tutorial are of the previous millennium. — StoryTeller - Unslander Monica, Sep 11 '17 at 12:19
@ishpreet - Then you can bring a standard quote supporting your claim. We'll wait here. — StoryTeller - Unslander Monica, Sep 11 '17 at 12:23
**Turbo C++** Compiler still accepts void return type, even though it has been discontinued. So still your statement The return type has to be `int` does not hold for the entire Cpp. — Ishpreet, Sep 11 '17 at 12:27
To quote well Modern Cpp or Standard Cpp only allows main to be `int`. — Ishpreet, Sep 11 '17 at 12:29

463035818_is_not_a_number · Accepted Answer · 2017-09-11T12:31:55.240

4

You need to declare functions before you call them, so you basically have 2 options:

Declare them before main:

int addition(int a, int b);
int substraction(int a, int b);

or move the whole definition of them in front of the main.

edited Sep 11 '17 at 12:31

answered Sep 11 '17 at 12:16

463035818_is_not_a_number

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score 1 · Answer 2 · answered Sep 11 '17 at 12:17

Just declare the functions before you use them, like this:

int addition(int a, int b);
int substraction(int a, int b);

and you will be fine.

Or, move the definitions (implementations) of your functions, before main().

PS: What should main() return in C and C++? An int, not void.

score 0 · Answer 3 · answered Sep 11 '17 at 12:16

The C++ compiler reads your code top to bottom. It is not aware of the existence of addition until it is declared - attempting to use it before a declaration is an error.

To fix your compiler error, move the definitions of addition and substraction above main.

score 0 · Answer 4 · answered Sep 11 '17 at 12:16

In C++ (and C99, C11 but not older C standards) you must declare functions before you can use them. This should be the same as the definition but without the body ({}) like what you find in header files.

int addition(int a, int b);
int substraction(int a, int b);
void main()
{
    ...

Error with compiling simple C++ application

4 Answers4