Error loading a no_caml_startup built library in dune utop

[k0pernicus]

First, thanks to all contributors for your work on ocaml-rs.

I successfully built my OCaml library (static and dynamic) from Rust code, and I wanted to try my Rust code using dune utop.
My function is pretty simple, and I don't initialize or use the OCaml runtime in this function.

As an example, it is not much difficult compared to:

#[ocaml::func]
#[ocaml::sig("unit -> string")]
pub fn process_string() -> &'static str {
    return "something"
}

In order to use my library in dune utop I used the no_caml_startup feature, and I have set the OCAML_INTEROP_NO_CAML_STARTUP environment variable.

The issue is, running dune utop, I have this error each time I call my Rust (to OCaml) function:

thread '<unnamed>' panicked at /Users/user/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ocaml-1.2.0/src/runtime.rs:43:9:
Rust code that is called from an OCaml program should not try to initialize the runtime.
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

thread '<unnamed>' panicked at library/core/src/panicking.rs:218:5:
panic in a function that cannot unwind
stack backtrace:
   0:        0x1043feb3c - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h6e25c13836847e70
   1:        0x104411db0 - core::fmt::write::h37cdb50ab8af3d55
   2:        0x1043fd1b0 - std::io::Write::write_fmt::hd4c273f34c4c0a33
   3:        0x1043fe9f0 - std::sys::backtrace::BacktraceLock::print::h1df7364dde63dc75
   4:        0x1043ff854 - std::panicking::default_hook::{{closure}}::h646e398272c5759a
   5:        0x1043ff648 - std::panicking::default_hook::hf65fd28e95db7176
   6:        0x1044000d0 - std::panicking::rust_panic_with_hook::hc9e2ec2a12b10e12
   7:        0x1043ffd20 - std::panicking::begin_panic_handler::{{closure}}::h3b6449e2eb83bf4c
   8:        0x1043feff0 - std::sys::backtrace::__rust_end_short_backtrace::h38d85099ddd107a3
   9:        0x1043ffa00 - _rust_begin_unwind
  10:        0x104416824 - core::panicking::panic_nounwind_fmt::hd8d3f0c92bbab643
  11:        0x10441689c - core::panicking::panic_nounwind::hd38337cbf8361018
  12:        0x104416940 - core::panicking::panic_cannot_unwind::h47d96b2bff7532cb
  13:        0x1043e2448 - _process_string
  14:        0x1042a26c8 - _caml_bytecode_interpreter
  15:        0x1042a3d3c - _caml_main
  16:        0x10428a48c - _main
thread caused non-unwinding panic. aborting.
[1]    61513 abort      OCAML_INTEROP_NO_CAML_STARTUP=1 dune utop

I checked in the ocaml-rs code and it seems the panic is done because I use the no_caml_startup feature:

ocaml-rs/src/runtime.rs

Line 42 in 9e91369

#[cfg(feature = "no-caml-startup")]

Do I have to change something in my build, or my configuration, in order to not initialize twice the runtime?

[k0pernicus]

For anyone asking why I use the no_caml_startup feature: if I don't use it the code panics each time I try to run dune utop in my test project.