/in/foo.c: In function 'work':
/in/foo.c:9:9: warning: 'return' with no value, in function returning non-void
         return;
         ^~~~~~
/in/foo.c:4:5: note: declared here
 int work(int a,int b,int c)
     ^~~~
/in/foo.c:16:5: warning: 'return' with no value, in function returning non-void
     return;
     ^~~~~~
/in/foo.c:4:5: note: declared here
 int work(int a,int b,int c)
     ^~~~
/in/foo.c: In function 'main':
/in/foo.c:20:9: warning: unused variable 'i' [-Wunused-variable]
     int i;
         ^