[...]$ ls /usr/lib/ocaml/compiler-libs/ | grep Cmo
[...]$

opam install base
The following actions will be performed:
  ∗ install base v0.12.2

<><> Gathering sources ><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[base.v0.12.2] found in cache

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ERROR] The compilation of base failed at "/home/meguru/.opam/opam-init/hooks/sandbox.sh build dune build -p base -j 7".

#=== ERROR while compiling base.v0.12.2 =======================================#
# context     2.0.4 | linux/x86_64 | ocaml-system.4.09.0 | https://opam.ocaml.org#867b7ac6
# path        ~/.opam/default/.opam-switch/build/base.v0.12.2
# command     ~/.opam/opam-init/hooks/sandbox.sh build dune build -p base -j 7
# exit-code   1
# env-file    ~/.opam/log/base-7179-d2c37b.env
# output-file ~/.opam/log/base-7179-d2c37b.out
### output ###
#       ocamlc compiler-stdlib/gen/.gen.eobjs/byte/gen.{cmi,cmo,cmt} (exit 2)
# (cd _build/default && /usr/bin/ocamlc.opt -w -40 -g -bin-annot -I compiler-stdlib/gen/.gen.eobjs/byte -I /usr/lib/ocaml/compiler-libs -no-alias-deps -o compiler-stdlib/gen/.gen.eobjs/byte/gen.cmo -c -impl compiler-stdlib/gen/gen.ml)
# File "compiler-stdlib/gen/gen.ml", line 59, characters 33-51:
# 59 |      let toc = (input_value ic : Cmo_format.library) in
#                                       ^^^^^^^^^^^^^^^^^^
# Error: Unbound module Cmo_format



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
┌─ The following actions failed
│ λ build base v0.12.2
└─ 
╶─ No changes have been performed