I am trying to separate my functions in another source file. But i am getting error that multiple definition on add function.
Main source file
Main.cpp
#include<iostream>
#include "myHeader.h"
using namespace std;
int main()
{
int result = add(1,2);
}
Header file "myHeader.h"
#include "calc.cpp"
int add(int, int);
Other Source file "calc.cpp"
int add(int a, int b)
{
return a+b;
}
What you need is:
"myHeader.h"
#ifndef MY_HEADER
#define MY_HEADER
int add(int, int);
#endif
calc.cpp
#include "myHeader.h"
int add(int a, int b)
{
return a+b;
}
main.cpp
#include "myHeader.h"
int main()
{
int result = add(1,2);
return 0;
}
You don't include the .cpp into the .h . The header file is used to tell the compiler the existence of a function with the specified prototype, but the liker will be tke care of matching up the call to a function with the implementation of that function.
Also, it's usually a good idea to give you header file and .cpp the same name, so calc.h and calc.cpp rather than myHeader.h.
Don't include calc.cpp from myHeader.h. Except for that one line, your example is right as far as headers go. (main() should return a value).
calc.cpp and main.cpp are two different "compilation units" which will be compiled separately into object files. The two object files are then combined into one executable by a linker.
calc.h which you've included from your main.cpp. Having the signature is sufficient for the compiler to generate the object file. The actual body of the function goes into the object file for calc.cpp. The linker's job is to combine all the code together, so it's really the linker that "finds" the actual compiled code of your function.You problem is that you include a Code File (cpp) into a header. You should do the inverse. Include your header "myHeader.h" into calc.cpp. And to be coherent, you should name your header the same name as your Code file, so calc.h for the header and calc.cpp for you code.
This is pretty simple. Do not Include your "calc.cpp" file in "MyHeader.h" file.
Take also a look at C/C++ IncludeGuard here
This is a fundamental of C/C++ programming. You will need to use it many times.
Protect your "myHeader.h"
#ifndef ADD_HEADER
#define ADD_HEADER
int add(int, int);
#endif // ADD_HEADER
#include "calc.cpp"
Don't do that - it includes the function definition in any translation unit that includes the header, so you'll end up with multiple definitions.
Without that, your code should be fine if you build a program from both source files. main.cpp will include a declaration, so that it knows that function exists; the definition from the other source file will be included in the program by the linker.
Do not include calc.cpp . This is causing the redefinition
you can include myHeader.h in calc.cpp
