Weird that this is about building a C compiler[0] in OCaml . I expected the implementation language to also be C both for consistency but also because i'm willing to bet that there are more people who can read C than OCaml. [0] actually from the readme in the github repo[1] it seems to be a C subset, not all of C [1] https://github.com/nlsandler/nqcc2
There are many disadvantages to writing a compiler in c (and I have done it). For me, the biggest is simply that it is very verbose for the type of things that you do commonly in a compiler. I have written a self-hosting compiler that transpiles to c and the generated code is about 5x as long as the original code. I could go through and clean it up and probably get it down to 2-3x, but there are certain concepts that cannot easily be expressed compactly in c (except possibly with preprocessor abuse that I don't have patience for). A simple example is that if you want to represent a union type you have to manually define 2 structs and an enum. Matching with switch is also verbose as you have to both match and manually assign the value in the match case. Again, you can use macros to do this though at that point you arguably aren't even using c but rather a hybrid language. A language like ocaml, makes it much more straightforward to define and match on unions as well as gives you other nice high level things like gc so you can focus on the compiler itself and not low level details.