/in/foo.c: In function 'IsPrime':
/in/foo.c:17:7: warning: statement with no effect [-Wunused-value]
       for(i;i<=sqrt(x);i++)
       ^~~
/in/foo.c: In function 'PrimeCount':
/in/foo.c:31:2: warning: statement with no effect [-Wunused-value]
  for(i;i<n;i++)
  ^~~
/in/foo.c: In function 'main':
/in/foo.c:42:5: warning: statement with no effect [-Wunused-value]
     for(i;i<n1;i++)
     ^~~
/in/foo.c:47:2: warning: statement with no effect [-Wunused-value]
  for(i;i<n2;i++)
  ^~~
/in/foo.c: In function 'IsPrime':
/in/foo.c:27:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^