No subject

I try to write a routine for class selection by mouse.
When I want to transform screen coordinates into earth coordinates
I get 'segmentation fault'.
Could somebody show me where is my fault ?

Code looks like this:
*********************
select_class_m(char *map, int *class, char label[], int *button)
{
int	x, y, button;
double	east, north;

R_open_driver();
D_setup(0);
R_get_location_with_pointer(&x,&y,&button);
east = D_d_to_u_col((double) x);	<- segmentation fault !
north = D_d_to_u_row((double) y);
R_close_driver();
	...
}
*******************

There are no warnings during compilation and linking.

Thanks in advance,
Robert Szczepanek
Cracow University of Technology, Poland
E-mail:  robert at profek.wis.pk.edu.pl