/in/foo.c: In function 'main':
/in/foo.c:19:17: warning: implicit declaration of function 'abs' [-Wimplicit-function-declaration]
     printf("%d",abs(x-y));
                 ^~~
/in/foo.c:19:22: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
     printf("%d",abs(x-y));
                     ~^~
/in/foo.c:19:22: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]