/in/foo.c:1:3: error: invalid preprocessing directive #-
 # -*- coding:utf-8 -*-
   ^
/in/foo.c:3:1: error: unknown type name 'def'
 def hui(s):
 ^~~
/in/foo.c: In function 'hui':
/in/foo.c:3:11: error: expected declaration specifiers before ':' token
 def hui(s):
           ^
/in/foo.c:3:5: warning: type of 's' defaults to 'int' [-Wimplicit-int]
 def hui(s):
     ^~~
/in/foo.c:7:9: warning: control reaches end of non-void function [-Wreturn-type]
         return s[0]==s[-1] and hui(s[1:-1])
         ^~~~~~