bug#43721: Package 'dune' (ocaml) is not Reproducible

[zimoun]

Dear,

Using Guix 04a459a, the classical:

   guix build dune
   guix build dune --no-grafts --check -K

return:

--8<---------------cut here---------------start------------->8---
guix build: error: derivation 
`/gnu/store/kg7mnb1b09n5zddgvc4hs8ira3i4jzz2-dune-1.11.3.drv' may not be 
deterministic: output `/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3' 
differs from ‘/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3-check’
--8<---------------cut here---------------end--------------->8---

then:

   diff -r --no-dereference 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3{,-check}
   
returns a large output (truncated here):

--8<---------------cut here---------------start------------->8---
Binary files 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3/lib/ocaml/site-lib/dune/configurator/configurator.cma
 and 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3-check/lib/ocaml/site-lib/dune/configurator/configurator.cma
 differ
Binary files 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3/lib/ocaml/site-lib/dune/configurator/configurator__Extract_obj.cmt
 and 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3-check/lib/ocaml/site-lib/dune/configurator/configurator__Extract_obj.cmt
 differ
Binary files 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3/lib/ocaml/site-lib/dune/configurator/configurator__V1.cmti
 and 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3-check/lib/ocaml/site-lib/dune/configurator/configurator__V1.cmti
 differ

[...]

Binary files 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3/lib/ocaml/site-lib/dune/_stdune/stdune__User_error.cmti
 and 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3-check/lib/ocaml/site-lib/dune/_stdune/stdune__User_error.cmti
 differ
Binary files 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3/lib/ocaml/site-lib/dune/_stdune/stdune__User_message.cmti
 and 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3-check/lib/ocaml/site-lib/dune/_stdune/stdune__User_message.cmti
 differ
Binary files 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3/lib/ocaml/site-lib/dune/_stdune/stdune__User_warning.cmti
 and 
/gnu/store/1wwdmzcjhrpal92sz2zwzhyqmbc3w7ri-dune-1.11.3-check/lib/ocaml/site-lib/dune/_stdune/stdune__User_warning.cmti
 differ
--8<---------------cut here---------------end--------------->8---


Is it expected?  Does it comes from timestamp?  Is it avoidable?


I have not tried (yet) with the patch [1] updating ’dune’.

[1] <http://issues.guix.gnu.org/issue/40091>

All the best,
simon