/in/foo.c:1:1: error: unknown type name 'def'
    1 | def is_palindrome(x):
      | ^~~
/in/foo.c: In function 'is_palindrome':
/in/foo.c:1:21: error: expected declaration specifiers before ':' token
    1 | def is_palindrome(x):
      |                     ^
/in/foo.c:1:5: warning: type of 'x' defaults to 'int' [-Wimplicit-int]
    1 | def is_palindrome(x):
      |     ^~~~~~~~~~~~~
/in/foo.c:12: warning: control reaches end of non-void function [-Wreturn-type]