How do I link LISP into my C project to do this safer copy you recommend ?

People are downvoting you, but as the author of this I can say you're right. Not necessarily lisp, but using any language that doesn't have the fatal flaw of totally broken strings is better.

C is still a large historical influence on many languages, and knowing it makes people more capable as programmers. That's why I teach it, and I use it because I'm just old like that. Once someone knows C they can fix all kinds of problems, and then can learn a huge number of languages fairly easily.

But these days, without a solid reason for using it, I'd avoid C and use a better alternative.