input data as a global

I want to use the input data in my functions. I don't understand how to do that correctly. I declare uPtrs as a global before calling all functions, but Matlab is shutdown... Thanks for any answer :)

... 
InputRealPtrsType uPtrs = 0;  - !!!

void spinDisplay() 
{ 
spin = spin + 10*(*uPtrs[i]); - !!!
if (spin > 360.0) 
spin = spin - 360.0; 
glutPostRedisplay(); 
} 
static void mdlOutputs(SimStruct *S, int_T tid) 
{ 
real_T *y = ssGetOutputPortRealSignal(S,0); 
real_T *x = ssGetContStates(S); 
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0); - !!!
int_T width = ssGetOutputPortWidth(S,0);

glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB); 
glutInitWindowSize (250, 250); 
glutInitWindowPosition (100, 100); 
glutCreateWindow ("hello"); 
init (); 
glutDisplayFunc(display); 
glutReshapeFunc(reshape); 
glutIdleFunc(spinDisplay); 
glutMainLoop(); 
}