Hello, I’m relatively new to OCaml and I’m using Ctypes to interface with a C library. I managed to get everything working but I ran into a few hiccups involving enums and I’m wondering if there is a better solution.
Example C enum:
typedef enum {
MyEnumA,
MyEnumB
} MyEnum;
On the Ocaml side, in the Types module:
(* The types of my_enum_a and my_enum_b are "int64 const" *)
let my_enum_a = constant "MyEnumA" int64_t
let my_enum_b = constant "MyEnumB" int64_t
Ctypes is great in that it automatically finds the size and values of the C enums (I’m using the Stub Generation with Dune Ctypes) . But there are times where it would be very convenient to work with these int64 const values directly. For example, this 2019 issue shows how to use a C enum as a bit flag. Reading the answers implies that in 2019 the Ctypes constant function created an int64, not an int64 const. That would be great because I know how to manipulate int64s. Support for const looks like it was committed in 2024.
I’ve tried searching the Ctypes github repo on how to convert an int64 const to an int64, but I haven’t found anything that has worked. Specifically I’ve tried using coerce and also views with no luck.
My workaround involves manually defining certain enum values in OCaml. But since Ctypes already has access to these values, it would be nice to not to have to duplicate work.