Header /file module issues

i am presently breaking a program down into seperate source files and writing some small header files also, everything has gone swimmingly but now i am hitting problems with the below..i am sure other problems of this sort will come up as i continue so id appreciate any advice...

this opening entry of my Graphics.h file works fine included in main and everything in there seems to use it fine, but when i include it in other source files i get a list of errors saying each element is being redefined..first defined here..etc.. even when the source file does not so far use anything in the header. on the other hand other headers dont give me any problem being put in more than one source, ...but then they only contain class definitions

Code:

---

#ifndef GRAPHICS_H_INCLUDED
#define GRAPHICS_H_INCLUDED


 SDL_Surface *screen;
 SDL_Surface *temp;
 SDL_Surface *PegArea;
 SDL_Surface *Buttonarea;
 SDL_Surface *Gameboard;


#endif // GRAPHICS_H_INCLUDED

---

if you are having redefinition problem then you must use extern

unfortunately that doubled the number of errors:-( i dunno whats going on, will have to read up more as this is new to me.

can you post some errors dude here :)

cheers... heres the build log...Graphics.h header to a working source file 'Buttonfunctions.cpp' to generate the errors

Quote:

---

In function `_ZN10MenuButton11InitButtonsEv':|
C:\Program Files\CodeBlocks\My Programs\ButtonFunctions.cpp|10|multiple definition of `_screen'|
C:\Program Files\CodeBlocks\My Programs\New SDL Project\.objs\SDLmain.o:C:\Program Files\CodeBlocks\My Programs\SDLmain.cpp|22|first defined here|

objs\ButtonFunctions.o||In function `_ZN10MenuButton11InitButtonsEv':|
C:\Program Files\CodeBlocks\My Programs\ButtonFunctions.cpp|10|multiple definition of `_temp'|
C:\Program Files\CodeBlocks\My Programs\New SDL Project\.objs\SDLmain.o:C:\Program Files\CodeBlocks\My Programs\SDLmain.cpp|22|first defined here|

.objs\ButtonFunctions.o||In function `_ZN10MenuButton11InitButtonsEv':|
C:\Program Files\CodeBlocks\My Programs\ButtonFunctions.cpp|11|multiple definition of `_PegArea'|
C:\Program Files\CodeBlocks\My Programs\New SDL Project\.objs\SDLmain.o:C:\Program Files\CodeBlocks\My Programs\SDLmain.cpp|23|first defined here|

\.objs\ButtonFunctions.o||In function `_ZN10MenuButton11InitButtonsEv':|
C:\Program Files\CodeBlocks\My Programs\ButtonFunctions.cpp|11|multiple definition of `_Buttonarea'|
C:\Program Files\CodeBlocks\My Programs\New SDL Project\.objs\SDLmain.o:C:\Program Files\CodeBlocks\My Programs\SDLmain.cpp|23|first defined here|

\.objs\ButtonFunctions.o||In function `_ZN10MenuButton11InitButtonsEv':|
C:\Program Files\CodeBlocks\My Programs\ButtonFunctions.cpp|12|multiple definition of `_Gameboard'|
C:\Program Files\CodeBlocks\My Programs\New SDL Project\.objs\SDLmain.o:C:\Program Files\CodeBlocks\My Programs\SDLmain.cpp|24|first defined here|

||=== Build finished: 10 errors, 0 warnings ===|

---

and i dont get the '`_ZN10MenuButton11InitButtonsEv' bit, whats the _ZN10 all about, and 'Ev' at end? i the 'MenuButton' is a class
and 'InitButtons is a member funtion, this member function is the only thing in the source file 'Buttonfunctions.cpp' and does not call anything from Graphics.h

i just saw that my obj files are being created in the folder 'New SDL Project' i dont know why that is, i think that needs sorting, they should be in my actual project folder somewhere right? i havent told the IDE to put them in NEW SDL_Project, but then i havent told it not to either...sigh

i tried to explain this problem what i am getting by a simple example

test.h

Code:

---

#ifndef INC_TEST_H_
#define INC_TEST_H_

#include <stdio.h>

int global_variable;

void show_test();

#endif // INC_TEST_H_

---

test.c

Code:

---

#include "test.h"

global_variable = 10;

void show_test() {
  printf("global_variable == %d\n", global_variable);
}

---

test1.h

Code:

---

#ifndef INC_TEST1_H_
#define INC_TEST1_H_

#include "test.h"

void show_test2();

#endif // INC_TEST1_H_

---

test1.c

Code:

---

#include "test1.h"

global_variable = 20;

void show_test2() {
  printf("global_variable == %d\n", global_variable);
}

---

main.c

Code:

---

#include "test.h"
#include "test1.h"

int main() {
  show_test();
  show_test2();
  return 0;
}

---

while building

Quote:

---

[rocky@localhost test]$ gcc test.c test1.c main.c
test.c:3: warning: data definition has no type or storage class
test1.c:3: warning: data definition has no type or storage class
test1.c: In function ‘show_test2’:
test1.c:6: warning: incompatible implicit declaration of built-in function ‘printf’
/tmp/ccisu68m.o:(.data+0x0): multiple definition of `global_variable'
/tmp/ccCehBee.o:(.data+0x0): first defined here
collect2: ld returned 1 exit status

---

what i am saying is that


test.h

Code:

---

#ifndef INC_TEST_H_
#define INC_TEST_H_

#include <stdio.h>

extern int global_variable;

void show_test();

#endif // INC_TEST_H_

---

test1.c

Code:

---

#include "test1.h"

//global_variable = 20;

void show_test2() {
  printf("global_variable == %d\n", global_variable);
}

---

By this you can have one defination of your variables which is declared in your graphics.h
I hope you understand what i try to say

well i not sure if i understand entirely what you are showing...i did however delete the include graphics.h from the test file and name the variables as 'extern' in the test file and the functions therein now recognise them,, thanks for your advice