At the cost of sounding naive and stupid

It may be a naive question, but it's a very important naive question. Naive doesn't mean bad.

The answer is that that is not possible, because the compiler is supposed to translate the very specific language of C into mostly very specific machine instructions. The programmers who wrote the code, did so because they usually expect a very specific behavior. So, that would be broken.

But also, the "unsafety" is in the behavior of the system and built into the language and the compiler.

It's a bit of a flawed comparison, but you can't build a house on a foundation of wooden poles, because of the advantages that wood offers, and then complain that they are flammable. You can build it in steel, but you have to replace all of the poles. Just the poles on the left side won't do.

And you can't automatically detect the unsafe parts and just patch those either. If we could, we could just fix them directly or we could automatically transpile them. Darpa is trying that at the moment.