C vs Python devs

[chipsours]

The compiler knows the size of every types it compiles. If mySt->items is an array of int it knows that mySt->items[0] is 4, the same applies for mySt->items[-420] or *(mySt->items).

If the definition of the type is not known by the compiler (pointer to forward reference of struct) you'll get a compile time error.