Hey everyone,

I have been following LazyFoo's tutorial series lately to learn a bit about using the SDL library within Visual C++ 2010 Express.

After completing his series, I went on to try and create an application that generates statistics for a character dependent on player input. Eg elf and human races will have different dexterity modifiers etc... Weapon attack will modify your atk modifier etc...

I am having a little linker trouble however. I have split my files up into .h and .cpp files so as to organise everything better. Here are my .h files:

This header is for general includes such as the SDL lib and the std includes
note: I have swapped the > symbols on these includes to " for the purpose of showing my code as the < symbols make whatever is inside them not show up here.
[source lang="cpp"]#ifndef GENHEADERS_H
#define GENHEADERS_H

//General header includes for the STD lib
//As well as other useful utilities

//SDL includes
#include "SDL.h"
#include "SDL_thread.h"
#include "SDL_image.h"
#include "SDL_mixer.h"

//basic utility includes
#include "string"
#include "cmath"
#include "fstream"

using namespace std;

#endif[/source]


This header is for storing my global variables. I have included the General header file here so as I can create SDL defined variables such as SDL_Surface.
[source lang="cpp"]#ifndef GLOBALS_H
#define GLOBALS_H

#include "GenHeaders.h"

bool quit = false;//This manages the game loop
SDL_Surface *screen;//The screen surface(duh)
SDL_Event event;//The event structure

//SDL surfaces
SDL_Surface* background;
SDL_Surface* playerDetailsBG;

//Screen State Variables
enum Screen { playerScreen, detailsScreen };
Screen currentScreen = playerScreen;

#endif[/source]

My constants header file is the same story as the globals, except that it holds onto my constants for me
[source lang="cpp"]#ifndef GENHEADERS_H
#define GENHEADERS_H

//General header includes for the STD lib
//As well as other useful utilities

//SDL includes
#include <SDL.h>
#include <SDL_thread.h>
#include <SDL_image.h>
#include <SDL_mixer.h>

//basic utility includes
#include <string>
#include <cmath>
#include <fstream>

using namespace std;

#endif[/source]

I have a general utilities header to hold global functions such as blitting one surface to another.
[source lang="cpp"]#ifndef UTILITIES_H
#define UTILITIES_H

#include "GenHeaders.h"

//General utility Functions
SDL_Surface *load_image( string fileName );//load an image
void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination, SDL_Rect* clip = NULL );

#endif[/source]

I also have created a header to hold my classes. As you can see I am working on creating a button.
[source lang="cpp"]#ifndef ACORNAPI_H
#define ACORNAPI_H

#include "AcnButton.h"

#endif[/source]

Here is my button header file. This is where the problems arise as the compiler complains that my global variables are already defined in AcnButton.obj

[source lang="cpp"]#ifndef ACNBUTTON_H
#define ACNBUTTON_H

#include "GenHeaders.h"
#include "utilities.h"
#include "globals.h"

///////////////
class AcnButton
///////////////
{
private:
SDL_Rect button;//The range of the background
SDL_Surface *buttonGraphic;//The button graphic
public:
AcnButton( int x, int y, int w, int h );//Constructor
~AcnButton();//Destructor
bool onButton();//Returns true when the given coordinates are within the button
void showButton( SDL_Surface *thisSurface );//applies the button to the given surface
};

#endif[/source]


And my main header.
[source lang="cpp"]#ifndef MAIN_H
#define MAIN_H

#include "AcornAPI.h"
#include "GenHeaders.h"
#include "utilities.h"
#include "globals.h"
#include "Constants.h"

bool initialise();//initialise anything that needs to be
void clean_up();//Frees anything that needs to be
void HandleWindowEvents ();//Handle Window Events
void LoadFiles ();//Load the required Source Files
void ShowBackground();//Show Background Image
void ShowDetails();

#endif[/source]


And my error when I try to compile is:
[source lang="cpp"]1>------ Build started: Project: Acorn, Configuration: Debug Win32 ------
1> AcnButton.cpp
1> Generating Code...
1> Compiling...
1> main.cpp
1> Generating Code...
1>main.obj : error LNK2005: "struct SDL_Surface * background" (?background@@3PAUSDL_Surface@@A) already defined in AcnButton.obj
1>main.obj : error LNK2005: "struct SDL_Surface * playerDetailsBG" (?playerDetailsBG@@3PAUSDL_Surface@@A) already defined in AcnButton.obj
1>main.obj : error LNK2005: "struct SDL_Surface * screen" (?screen@@3PAUSDL_Surface@@A) already defined in AcnButton.obj
1>main.obj : error LNK2005: "union SDL_Event event" (?event@@3TSDL_Event@@A) already defined in AcnButton.obj
1>main.obj : error LNK2005: "bool quit" (?quit@@3_NA) already defined in AcnButton.obj
1>main.obj : error LNK2005: "enum Screen currentScreen" (?currentScreen@@3W4Screen@@A) already defined in AcnButton.obj
1>C:\Users\Me\Documents\Vis C++ Express 2010\Acorn\Debug\Acorn.exe : fatal error LNK1169: one or more multiply defined symbols found
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========[/source]

Now I am assuming it is an error in the header files. Somehow the globals.h is getting included more than once. I have added #ifndef #define #endif to the headers to try and prevent this however.

Does anyone know what I'm missing here?
Perhaps t isn't a problem with the headers, but a problem with the .cpp files?

Please let me know if the headers are fine so as I may pinpoint the source of the issue.

Thank you!

You probably want to read this article on organizing code files in C and C++. In particular look at problem 4 in the article.

Thank you guys
I'ts working fine now

I appreciate the help and links