What is the actual catch with Fil-C? Memory safety for C based projects without a complete rewrite sounds like a very good idea, but there must be some pitfalls in this approach which this would not work in some cases.

In some other memory-safety circles (Rust, Zig, etc) I'm going to expect that this is going to be heavily scrutinized over the claims made by the author of Fil-C.

But great work on this nonetheless.