Error LNK2005 in c program

Question

When I tried to run the program, visual studio showed the errors LNK2005 and LNK1169.

I created two source files and I use #include in main file. Could someone tell me why it is wrong

Here is my code in 1.5.3.cpp

#include "stdafx.h"
#include "Print.cpp"

    int main()
{
    double b;
    printf("Input a number\n");
    scanf_s("%lf\n", &b);
    print(b);//call print()
    return 0;
}

And here is my code in Print.cpp

#include "stdafx.h"

void print(double a)
{
    double c = a * 2;
    printf("%lf multyply by 2 is %lf", a, c);

}

Including the error messages in your question may be of help. — Curt Nichols, Jan 25 '18 at 23:24
So VS gave you only the text *Errors LNK2005 and LNK1169*? No other information? No text description, no line numbers, no code, absolutely **nothing** but *Errors LNK2005 and LNK1169*? I find that somewhat hard to believe. You have the error messages right on the screen in front of you; why aren't they in your post where we have that information as well? — Ken White, Jan 25 '18 at 23:25
@WeatherVane: VS defaults all source files to `*.cpp`. You have to rename them if you want `.c` files. — Mark Benningfield, Jan 25 '18 at 23:41
@KenWhite: This is not an external library problem. This is a lack of a header include. — Mark Benningfield, Jan 25 '18 at 23:43
@MarkBenningfield: OK. It's still a VLQ post that fails to include the relevant details and is mistagged. — Ken White, Jan 25 '18 at 23:47
@KenWhite: Concur, except that I'm pretty sure the OP is attempting this in C, it's just that they don't know how to make VS behave. — Mark Benningfield, Jan 25 '18 at 23:49

MFisherKDX · Accepted Answer · 2018-01-26T00:06:14.527

This is your problem:

#include "Print.cpp"

This defines the function void print(double a) in both the Print.cpp file AND the 1.5.3.cpp file. When the 1.5.3.cpp file is compiled it produces a symbol void print(double a) in the 1.5.3.obj file. Similarly, when the Print.cpp file is compiled, it also produces a symbol void print(double a) in the Print.obj file. Thus the linker errors:

LNK2005 "void __cdecl print(double)" (?print@@YAXN@Z) already defined in 1.5.3.obj LNK1169 one or more multiply defined symbols found

You need to declare void print(double a) in a Print.h file and #include it in the 1.5.3.cpp and Print.cpp files.

You may want to see: What is the difference between a definition and a declaration?

Error LNK2005 in c program

1 Answers1