Recursive definitions of values and bytecode calls to primitives

Question

I'm trying to generate OCaml bytecode containing C_CALLs to these primitives:

caml_alloc_dummy
caml_alloc_dummy_function
caml_update_dummy
caml_alloc_dummy_float

which are all related to recursive definition of values (see <ocamlsource>/bytecomp/bytegen.ml)

To generate calls to the first three, this code is enough:

let rec myval = (f, 1, myval)
and f _ = match myval with (_, x, _) -> x;;

but I cannot imagine a piece of code for the last one, which should be specifically related to recursive definitions of float arrays.

Answer 1

This seems to do it (testing with 4.03.0):

type t = { x : float }

let rec r = { x = 0.1 +. 0.2 }

Yes, the rec is useless, but the bytecode compiler isn't smart enough to see that. Note that records in which every field is a float are represented specially, with the floats unboxed.

The generated bytecode:

const 1
ccall caml_alloc_dummy_float, 1
push
const 0.2
push
const 0.1
ccall caml_add_float, 2
makefloatblock 1
push
acc 1
ccall caml_update_dummy, 2
event "_none_" -1--1
acc 0
makeblock 1, 0
pop 1
setglobal Test!