# Fatal error: cannot load shared library dllext\_stubs **URL:** \ **Category:** Learning\ **Tags:** ocamldebug\ **Created:** [May 21, 2025, 1:01pm UTC](https://discuss.ocaml.org/t/fatal-error-cannot-load-shared-library-dllext-stubs/16680 "2025-05-21T13:01:56Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![nojaf](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojaf/32/5587_2.png) [@nojaf](https://discuss.ocaml.org/u/nojaf)\ **Post date:** [May 21, 2025, 1:01pm UTC](https://discuss.ocaml.org/t/fatal-error-cannot-load-shared-library-dllext-stubs/16680/1 "2025-05-21T13:01:56Z")
So, I want to give `ocamldebug` a shot. Using latest Mac and OCaml 5.3.0: ```auto nojaf@nojaf-mbp rescript % dune build nojaf@nojaf-mbp rescript % ocamldebug _build/default/analysis/bin/main.bc OCaml Debugger version 5.3.0 (ocd) break @Main 92 Loading program... Fatal error: cannot load shared library dllext_stubs Reason: dlopen(dllext_stubs.so, 0x000A): tried: 'dllext_stubs.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OSdllext_stubs.so' (no such file), '/usr/lib/dllext_stubs.so' (no such file, not in dyld cache), 'dllext_stubs.so' (no such file) (ocd) ``` Where should `dllext_stubs.dylib` be coming from? ---
**Author:** ![nojb](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojb/32/519_2.png) [@nojb](https://discuss.ocaml.org/u/nojb)\ **Post date:** [May 21, 2025, 1:37pm UTC](https://discuss.ocaml.org/t/fatal-error-cannot-load-shared-library-dllext-stubs/16680/2 "2025-05-21T13:37:08Z")
You can use the environment variable `CAML_LD_LIBRARY_PATH` to specify where to look up shared libraries containing native stubs (see [OCaml - The runtime system (ocamlrun)](https://ocaml.org/manual/5.3/runtime.html)). Dune places the stubs of native (public) libraries in `_build/install/default/lib/stublibs`. Did you try `dune exec -- ocamldebug ...`? Cheers, Nicolas ---
**Author:** ![nojaf](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojaf/32/5587_2.png) [@nojaf](https://discuss.ocaml.org/u/nojaf)\ **Post date:** [May 21, 2025, 1:40pm UTC](https://discuss.ocaml.org/t/fatal-error-cannot-load-shared-library-dllext-stubs/16680/3 "2025-05-21T13:40:19Z")
I don’t seem to have any files there: ```auto nojaf@nojaf-mbp rescript % ls _build/install/default/lib/stublibs ls: _build/install/default/lib/stublibs: No such file or directory nojaf@nojaf-mbp rescript % dune exec -- ocamldebug /Users/nojaf/Projects/rescript/_build/default/analysis/bin/main.bc OCaml Debugger version 5.3.0 (ocd) break @Main 92 Loading program... Fatal error: cannot load shared library dllext_stubs Reason: dlopen(dllext_stubs.so, 0x000A): tried: 'dllext_stubs.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OSdllext_stubs.so' (no such file), '/usr/lib/dllext_stubs.so' (no such file, not in dyld cache), 'dllext_stubs.so' (no such file) (ocd) ``` `CAML_LD_LIBRARY_PATH` rings a bell, but I have no clue where to point it. ---
**Author:** ![nojb](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojb/32/519_2.png) [@nojb](https://discuss.ocaml.org/u/nojb)\ **Post date:** [May 21, 2025, 1:43pm UTC](https://discuss.ocaml.org/t/fatal-error-cannot-load-shared-library-dllext-stubs/16680/4 "2025-05-21T13:43:29Z")
Hard to say with the available information. You may want to make your code available somewhere in order to get better advice. Cheers, Nicolas ---
**Author:** ![nojaf](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojaf/32/5587_2.png) [@nojaf](https://discuss.ocaml.org/u/nojaf)\ **Post date:** [May 21, 2025, 1:45pm UTC](https://discuss.ocaml.org/t/fatal-error-cannot-load-shared-library-dllext-stubs/16680/5 "2025-05-21T13:45:04Z")
Yeah, I understand it is not much to go on. The code is available on [GitHub - rescript-lang/rescript: ReScript is a robustly typed language that compiles to efficient and human-readable JavaScript.](https://github.com/rescript-lang/rescript) It has a few project and I’m trying to debug the `analysis` project. Maybe I’m missing some dune flags ---
**Author:** ![nojb](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojb/32/519_2.png) [@nojb](https://discuss.ocaml.org/u/nojb)\ **Post date:** [May 21, 2025, 4:29pm UTC](https://discuss.ocaml.org/t/fatal-error-cannot-load-shared-library-dllext-stubs/16680/6 "2025-05-21T16:29:24Z")
> [@nojaf](#): > > `CAML_LD_LIBRARY_PATH` rings a bell, but I have no clue where to point it. I don’t have a Reason toolchain to try it, but a quick look at the source indicates that the missing stubs are those of the library `compiler/ext`. You may want to look into `_build/default/compiler/ext` to see if you find your missing shared library. Cheers, Nicolas ---
**Author:** ![nojaf](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojaf/32/5587_2.png) [@nojaf](https://discuss.ocaml.org/u/nojaf)\ **Post date:** [May 22, 2025, 6:46am UTC](https://discuss.ocaml.org/t/fatal-error-cannot-load-shared-library-dllext-stubs/16680/7 "2025-05-22T06:46:54Z")
The Reason toolchain isn’t required here. ReScript compiler is in OCaml, but doesn’t use Reason. Could I just be missing a dependency? I think at some point it was inside `_build/default/compiler/ext`. Seems no longer to be the case. Update: ```auto ls /Users/nojaf/Projects/rescript/_build/default/compiler/ext/*.so /Users/nojaf/Projects/rescript/_build/default/compiler/ext/dllext_stubs.so ``` Using `CAML_LD_LIBRARY_PATH=/Users/nojaf/Projects/rescript/_build/default/compiler/ext`: Now leads to ```auto Loading program... Fatal error: cannot load shared library dllbase_internalhash_types_stubs Reason: dlopen(dllbase_internalhash_types_stubs.so, 0x000A): tried: 'dllbase_internalhash_types_stubs.so' (no such file), '/System/Volumes/Preboot/Cryptexes/OSdllbase_internalhash_types_stubs.so' (no such file), '/usr/lib/dllbase_internalhash_types_stubs.so' (no such file, not in dyld cache), 'dllbase_internalhash_types_stubs.so' (no such file) (ocd) % ``` Okay, I figured it out. I need to append that `_build/default/compiler/ext` path to `CAML_LD_LIBRARY_PATH` `export CAML_LD_LIBRARY_PATH="$CAML_LD_LIBRARY_PATH:_build/default/compiler/ext"`