/in/foo.cc: In function 'int main()':
/in/foo.cc:20:6: warning: statement has no effect [-Wunused-value]
   abs(ans);
   ~~~^~~~~
/in/foo.cc:23:7: warning: unused variable 'ans' [-Wunused-variable]
   int ans=0;
       ^~~
/in/foo.cc:27:6: warning: statement has no effect [-Wunused-value]
   abs(ans);
   ~~~^~~~~
/in/foo.cc: In function 'int abs(int)':
/in/foo.cc:35:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^