Question

I have two header files:

DirectX_Engine.h

#pragma once
#include "Main.h"
#include <d3d9.h>

and:

Main.h

#pragma once
#include <Windows.h>
#include "DirectX_Engine.h"

int imRunning = 1;

After compiling, I get the following linker errors:

error LNK1169: one or more multiply defined symbols found
error LNK2005: "int imRunning" (?imRunning@@3HA) already defined in DirectX_Engine.obj

I’m also getting a ‘file is not found or directory doesn’t exist error’ when #includeing “d3dx9.h”. Any idea?

Answer 1

Two ideas. Firstly, you are including DirectX_Engine.h in Main.h and Main.h in DirectX_Engine.h. This will obviously not work.

Secondly, int imRunning gets included to each .cpp file that includes Main.h and the compiler treats it as a definition. Then the linker comes and sees imRunning defined in each of these files and doesn’t know what to do. The solution is using extern:

In Main.h:

extern int imRunning;

In one of the .cpp files:

int imRunning = 1;