[BUG] graphics bindings (open_canvas) work only when built with "dune build --release"

[adept]

Describe the bug

1. Clone the project https://github.com/adept/ocaml-canvas-test

2. Build it with dune build canvas.bc.js

3. Run it with index.html supplied

4. Observe runtime error

     canvas.bc.js:164237 Uncaught ReferenceError: caml_gr_state_create is not defined
     at open_canvas (canvas.bc.js:164237)
     at caml_call1 (canvas.bc.js:164415)
     at onload (canvas.bc.js:164438)
     at caml_call1 (canvas.bc.js:152942)
     at canvas.bc.js:154769

Indeed, there is no caml_gr_state_create in scope (but there is jsoo_runtime.caml_gr_state_create)

5. Build the project with "dune build --release canvas.bc.js"

6. Observe that it is working now.

Expected behavior
Non-release build should work as well

Versions

• ocamlc 4.09.1
• js_of_ocaml 3.6.0

[dbuenzli]

It seems graphics is using an at_exit handler I didn't look into the details (the error is a bit weird) but I suspect you are running into #1033.

[hhugo]

Graphics_js is using Js.Unsafe.variable instead of external to refer to stubs