fixing multipe definition error caused by including .cpp

[mew]

last night my friend send a code for me because he couldn't compile it.I checked the makefile and saw that he wasn't linked one of .o files.I fixed that.then I got multiple definition error.i opened .h files and wrote #ifndef,#define,#endif for all of them.then again i got the multiple definition error.so i opened all 3 .h files and saw something unusual.he included one .cpp file in header of two class.so i searched on Internet and found out that you should never include .cpp file and that caused the problem.but problem is the .cpp file that he included is not a class, it just contains 3 functions and i can't write a header for it and handle it like a class.how i could fix this problem?
global_functions.cpp(the cpp that he included and causing problem)

#include <string>
#include <iostream>
SDL_Surface *load_image( std::string filename )
{
	SDL_Surface* loadedImage = NULL;
	SDL_Surface* optimizedImage = NULL;
	loadedImage = SDL_LoadBMP( filename.c_str() );
	if( loadedImage != NULL )
	{
		optimizedImage = SDL_DisplayFormat( loadedImage );
		SDL_FreeSurface( loadedImage );
	}
	return optimizedImage;
}

void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination )
{
	SDL_Rect offset;
	offset.x = x;
	offset.y = y;
	SDL_BlitSurface( source, NULL, destination, &offset );
}

bool OnDraw(SDL_Surface* Surf_Dest, SDL_Surface* Surf_Src, int X, int Y, int X2, int Y2, int W, int H) 
{
	if(Surf_Dest == NULL || Surf_Src == NULL) {
		return false;
	}
	SDL_Rect DestR;
	DestR.x = X;
	DestR.y = Y;
	SDL_Rect SrcR;
	SrcR.x = X2;
	SrcR.y = Y2;
	SrcR.w = W;
	SrcR.h = H;
	SDL_BlitSurface(Surf_Src, &SrcR, Surf_Dest, &DestR);
	return true;
}

shower.h(global_functions.cpp included on it)

#ifndef __SHOWER_H
#define __SHOWER_H
#include "SDL/SDL.h"
#include "SDL/SDL_gfxPrimitives.h"
#include "define.cpp"
#include "global_functions.cpp"
#include <string>
class Shower {
    private:
        SDL_Surface* screen;
        int where; // :|
        SDL_Surface* safhe;
        int width;
    public:
        void showMap();
        void showMario();
        void showEnemies();
        void showMashrums();
        void show_screen();
        void setWidth(int x);
        Shower(SDL_Surface* _screen, int _where, int _width);
};
#endif 

mario.h(other header that global_functions.cpp included on it)

#ifndef __MARIO_H
#define __MARIO_H
#include <iostream>
#include <string>
#include "define.cpp"
#include "SDL/SDL.h"
#include "map.h"
#include "SDL/SDL_gfxPrimitives.h"
#include <cmath>
#include "SDL/SDL_image.h"
#include "global_functions.cpp"
using namespace std;

struct Point {
    double x, y;
};
class Mario {
    private:
        Point point;
        int type;
        int mtype;
        int life;
        Map* map;
        double speed;
        SDL_Surface* mini, *screen;
        int t;
    public:
        bool can(Point p);
        void move(int type);
        void gravity();
        Mario(int _life, Point _point, Map* _map, SDL_Surface* scr);
        bool die();
        void fraction();
        void show();
        int getTime();
        void setTime(int _time);
};
#endif 

main.cpp

#include "map.h"
#include "shower.h"
#include <iostream>
#include <string>
#include "SDL/SDL.h"
#include "SDL/SDL_gfxPrimitives.h"
#include "mario.h"

using namespace std;

int main()
{
    SDL_Surface* screen = SDL_SetVideoMode(256, 224, 24, SDL_HWSURFACE);
    Map* map = new Map;
    map->loadMap("world1-1.txt");
    Shower* show = new Shower(screen, 0, map->getWidth());
    SDL_Event event;
    show->showMap();
    Point p;
    p.x = 176;
    p.y = 200;
    Mario* mario = new Mario (3, p, map, screen);
    while(1)
    {
        while(SDL_PollEvent( &event ))
        {
            if(event.type == SDL_QUIT)
                return 0;
        }
        show->show_screen();
        mario->setTime(mario->getTime() + 1);
        mario->show();
    }
}

Makefile

all: define.cpp shower.cpp map.cpp main.cpp map.h shower.h shower.o map.o global_functions.cpp mario.o Mario.cpp mario.h
g++ main.cpp shower.o map.o Mario.o -lSDL -lSDL_gfx -lSDL_image -o mario
shower.o: shower.h shower.cpp
g++ shower.cpp -c -lSDL -lSDL_gfx -lSDL_image
map.o: map.h map.cpp
g++ map.cpp -c -lSDL -lSDL_gfx
mario.o: mario.h Mario.cpp
g++ -c Mario.cpp -lSDL -lSDL_gfx -lSDL_image
clean:
rm -rf *.o

some parts of error(after typing make on terminal)
g++ shower.cpp -c -lSDL -lSDL_gfx -lSDL_image
g++ map.cpp -c -lSDL -lSDL_gfx
g++ -c Mario.cpp -lSDL -lSDL_gfx -lSDL_image
g++ main.cpp shower.o map.o Mario.o -lSDL -lSDL_gfx -lSDL_image -o mario
In file included from mario.h:11:0,
from main.cpp:7:
global_functions.cpp: In function ‘SDL_Surface* load_image(std::string)’:
global_functions.cpp:8:14: error: redefinition of ‘SDL_Surface* load_image(std::string)’
SDL_Surface *load_image( std::string filename )
^
In file included from shower.h:10:0,
from main.cpp:2:
global_functions.cpp:8:14: error: ‘SDL_Surface* load_image(std::string)’ previously defined here
SDL_Surface *load_image( std::string filename )
^

[firedraco]

As you noted, the problem is that you are including a .cpp file.

You can create a .h file for files that just contain functions; they just need to contain the prototypes.

[mew]

thanks for reply firedraco
i created a global_function.h just as you said, changed those included .cpp to .h and added a compile option for global_functions.cpp on my makefile to create a global_functions.o for me and linked it.
Problem Solved.