Compilare: user.c: In function ‘compare_x’: user.c:55:3: warning: implicit declaration of function ‘compare_y’ [-Wimplicit-function-declaration] return compare_y(a, b); ^ user.c:60:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.c: In function ‘compare_y’: user.c:70:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.c: In function ‘closest_pair_dist’: user.c:189:1: warning: control reaches end of non-void function [-Wreturn-type] } ^