Undefined reference to static variable in c++ - c++

Question

I'm trying to use a static variable in one of my classes. I've used them before, without problem. Now I'm getting this error:
/tmp/ccg26aZi.o: In function 'main': main.cpp:(.text+0x7482):
undefined reference to `Rect::rect_change' collect2: error: ld
returned 1 exit status make: *** [exe] Error 1
any advice? Thanks!
UPDATE:
I was told to check my make file to make sure the rect.cpp was being included in the making of the exe. I switched the folder so it is in the correct place. But now I'm getting a whole new set of errors, I previously didn't get:
I checked my make file and made sure the rect.cpp, and moved it to a different folder that ran *.cpp. However Now I'm getting a brand new set of errors:
includes/Rect.h:16:17: error: ‘SDL_Rect’ does not name a type Rect(const SDL_Rect & r)
includes/Rect.h:16:28: error: ISO C++ forbids declaration of ‘r’ with no type [-fpermissive] Rect( const SDL_Rect & r)
includes/Rect.h:19:2: error: ‘SDL_Rect’ does not name a type
SDL_Rect getSDL_Rect() ^ includes/Rect.h: In constructor
‘Rect::Rect(const int&)’: includes/Rect.h:17:9: error: request for
member ‘x’ in ‘r’, which is of non-class type ‘const int’ : x(r.x),
y(r.y), w(r.w), h(r.h)
includes/Rect.h:17:17: error: request for member ‘y’ in ‘r’, which is
of non-class type ‘const int’ : x(r.x), y(r.y), w(r.w), h(r.h)
includes/Rect.h:17:25: error: request for member ‘w’ in ‘r’, which is
of non-class type ‘const int’ : x(r.x), y(r.y), w(r.w), h(r.h)
includes/Rect.h:17:33: error: request for member ‘h’ in ‘r’, which is
of non-class type ‘const int’ : x(r.x), y(r.y), w(r.w), h(r.h)
Here is the contents of my make file. the rect.cpp is located inside the src folder.
exe: main.cpp
g++ *.cpp src/*.cpp src/*.c `sdl-config --cflags --libs` -lSDL_image -lSDL_mixer -lSDL_ttf -Iincludes
run:
./a.out
r:
./a.out
clean:
rm a.out
c:
rm a.out
// header
#ifndef RECT_H
#define RECT_H
#include <iostream>
class Rect
{
public:
Rect(int x0 = 0, int y0 = 0, int w0 = 0, int h0 = 0)
: x(x0), y(y0), w(w0), h(h0)
{}
Rect( const SDL_Rect & r)
: x(r.x), y(r.y), w(r.w), h(r.h)
{}
SDL_Rect getSDL_Rect()
{
SDL_Rect r = {x, y, w, h};
return r;
}
int x, y, w, h;
static int rect_change;
static int rect_change_max;
};
inline std::ostream & operator<<(std::ostream & cout, const Rect & r)
{
cout << "(" << r.x << "," << r.y << "," << r.w << "," << r.h << ")";
return cout;
}
#endif
rect.cpp
#include "Rect.h"
int Rect::rect_change = 0;
int Rect::rect_change_max = 0;
// main.cpp example
#include "Rect.h"
int main()
{
Rect rect;
rect.rect_change = 5;
return 0;
}

Answer 1

Thanks for all the help, and thank you RichieHindle for the answer.
I needed to #include "SDL_gfxPrimitives.h" to get it to work. Funny that is the case because I've been working on this project for a while, and the compiler didn't complain at all, until I tried to add a static member.
Thanks again!