/in/foo.c: In function 'main':
/in/foo.c:13:13: warning: format '%d' expects argument of type 'int *', but argument 2 has type 'int' [-Wformat=]
     scanf("%d %d",year, month);
             ^
/in/foo.c:13:16: warning: format '%d' expects argument of type 'int *', but argument 3 has type 'int' [-Wformat=]
     scanf("%d %d",year, month);
                ^
/in/foo.c:31:8: warning: multi-character character constant [-Wmultichar]
   case '10': print_day(31);break;
        ^~~~
/in/foo.c:32:8: warning: multi-character character constant [-Wmultichar]
   case '11': print_day(30);break;
        ^~~~
/in/foo.c:33:8: warning: multi-character character constant [-Wmultichar]
   case '12': print_day(31);break;
        ^~~~
/in/foo.c:13:5: warning: 'year' is used uninitialized in this function [-Wuninitialized]
     scanf("%d %d",year, month);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.c:13:5: warning: 'month' is used uninitialized in this function [-Wuninitialized]