"unknown C primitive unix_has_symlink" error in VSCode debugger

[ewan-delanoy]

Hello, this example has just one file called debugged.ml with only one breakpoint
to set in it, at line 6288.
The contents of debugged.ml are available at https://github.com/ewan-delanoy/hello-world/tree/master

Debugging outside VSCode works (terminal output below) but when I try to do it
inside VSCode I get a "unknown C primitive unix_has_symlink" error message.

$ ocamlc -g -bin-annot str.cma unix.cma debugged.ml -o debugged.ocaml_debuggable
$ ocamldebug debugged.ocaml_debuggable
OCaml Debugger version 4.04.1

(ocd) break @debugged 6288
Loading program... done.
Breakpoint 1 at 221080: file debugged.ml, line 6288, characters 38-76
(ocd) r
Time: 359853 - pc: 221080 - module Debugged
Breakpoint: 1
6288 let h2=Sc_option.find_really (fun x-><|b|>x.Sc_beaver_for_statement.name="echo2")
(ocd) q
Removed breakpoint 1 at 221080: file debugged.ml, line 6288, characters 38-76

[hackwaly]

I can't reproduce your problem.

[ewan-delanoy]

Some more details then :
I'm using OCaml 4.04.1 on my Mac 10.11.3.
Here is the exact sequence of what I did :

1. Open the debugged.ml file , using open -a /Applications/Visual Code Studio.app in the terminal.
2. Inside VScode, open the folder containing the debugged.ml file
3. Click "Start debugging" in the menu
4. Check the launch.json file (see image below)
5. Set the breakpoint by putting a red circle with the mouse, at line 6288 in the debugged.ml file
6. Launch the debugging process by clicking on the green arrow (as in the image of my first post)

Did you do additional steps or did you some step differently ?

Note : when I set stopOnEntry to true, I get the same error message, "Fatal error: unknown C primitive `unix_has_symlink'" but without the "Lost connection" part.

[hackwaly]

No, I do debug as same as you

[hackwaly]

I can provide my working project to you. Did you need it?

[ewan-delanoy]

What is your "working project" ?
I'm curious to know if I could do some more in-depth debugging about this.

[hackwaly]

test_vscode.zip

[ewan-delanoy]

It seems that the problem comes from a version mismatch : see https://discuss.ocaml.org/t/unknown-c-primitive-unix-has-symlink-in-vscode-debugger/415/3

Perhaps the problem will disappear if you upgrade the debugger version inside VSCode