type information in a lisp: DA STANDARD way

so I'm making a toy s-expression parser in C which may or may not become a minimal toy lisp interpreter and I'm trying to figure out the best way to do types. I know the classic way is to use the end of the pointer as tag bits but it doesn't really look standard-conforming or portable.

is there a way of doing it that doesn't rely on undefined behavior? the only thing I can think of is making a struct that holds value/pointer and type information but this seems very wasteful.

>>18

that is a wrapper around it

Does not need to be.

it doesn't work on windows.

Sure it does. There are implementations of it on top of NT and even the winapi.

>>25
You are just too stupid to make a lisp. Better give up.
In my lisp I did something like what Arthur said. When I parsed the sexpr I kept the symbols as strings and returned a different, "lisp object" structure from functions that process the sexpr structure (like the evaluator).