> Only way around the type system is void, explicit casts and I guess unions.

And typedefs. Given that there's no parametric types, you run into void* quite frequently as well, so saying "only" inaccurately minimizes the scale of how much C code isn't strictly type safe.

Right, void* is used quite a lot for "generic" data structures. But I'm not sure that's what he meant. The reason I said "only" was that from my own experience, most C data structures are tailored for a specific use and so I don't see void* too much in this context.

And may I ask why you say "typedef" is unsafe? It is merely a type alias, like e.g. Haskell's and ML's "type", or isn't it?

> It is merely a type alias, like e.g. Haskell's and ML's "type", or isn't it?

It is, but it freely allows conversion between the aliased types.

    typedef int Feet;
    typedef int Meters;

    int main() {
      Feet height = 6;
      Meters inEngland = height; // <-- OK. :(
    }

I'm pretty sure you and the parent were thinking of Haskell's `newtype` not `type`

λ> :{

Prelude| type Feet = Int

Prelude| type Metres = Int

Prelude| :}

λ> let a = 5 :: Feet

λ> let b = 4 :: Metres

λ> :t a

a :: Feet

λ> :t b

b :: Metres

λ> a + b

9

λ> let f = id :: Feet -> Feet

λ> f b

4