The types of values and legal conversions between them are well defined in C -- the assumption that everything is just a block of bytes and hence may be casted freely between types is explicitly incorrect (and is what may lead to bad/invalid C code).
However, C does allow you to write code that can not proven to be legal with respect to the formal system of the language and get it to compile, I think that is what you are referring to.
But just because you can write an invalid program does not mean the type system doesn't exist or is flawed. I can also write an invalid Haskell program.
The difference between these two would be that the haskell program can be proven to contain only operations that map to well-defined operations in the formal language model by an automated process, while the same can not be done for C in the general case.
However, just because you can not always prove conformance to a formal model using automated means, doesn't mean that no formal model exists (because it does!).
However, C does allow you to write code that can not proven to be legal with respect to the formal system of the language and get it to compile, I think that is what you are referring to.
But just because you can write an invalid program does not mean the type system doesn't exist or is flawed. I can also write an invalid Haskell program.
The difference between these two would be that the haskell program can be proven to contain only operations that map to well-defined operations in the formal language model by an automated process, while the same can not be done for C in the general case.
However, just because you can not always prove conformance to a formal model using automated means, doesn't mean that no formal model exists (because it does!).