opam install num fails

[haansn08]

I am trying to install num using opam. However the build fails with following message:

# ocamlfind: Package num is already installed
#  - (file /home/dev/.opam/default/lib/num/META already exists)

Full output

[dev@localhost ~]$ eval $(opam env)
[dev@localhost ~]$ opam show num

<><> num: information on all versions <><><><><><><><><><><><><><><><><><><><><>
name         num
all-versions 0  1.0  1.1  1.2  1.3  1.4

<><> Version-specific details <><><><><><><><><><><><><><><><><><><><><><><><><>
version       1.4
repository    default
url.src:      "https://github.com/ocaml/num/archive/v1.4.tar.gz"
url.checksum:
          "md5=cda2b727e116a0b6a9c03902cc4b2415"
          "sha512=0cc9be8ad95704bb683b4bf6698bada1ee9a40dc05924b72adc7b969685c33eeb68ccf174cc09f6a228c48c18fe94af06f28bebc086a24973a066da620db8e6f"
homepage:     "https://github.com/ocaml/num/"
bug-reports:  "https://github.com/ocaml/num/issues"
dev-repo:     "git+https://github.com/ocaml/num.git"
authors:      "Valérie Ménissier-Morain" "Pierre Weis" "Xavier Leroy"
maintainer:   "Xavier Leroy <[email protected]>"
license:      "LGPL-2.1-only with OCaml-LGPL-linking-exception"
depends:      "ocaml" {>= "4.06.0"} "ocamlfind" {build & >= "1.7.3"}
conflicts:    "base-num"
synopsis      The legacy Num library for arbitrary-precision integer and rational arithmetic
[dev@localhost ~]$ opam install num
The following actions will be performed:
  ∗ install ocamlfind 1.9.1 [required by num]
  ∗ install num       1.4
===== ∗ 2 =====
Do you want to continue? [Y/n] y

<><> Gathering sources ><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[num.1.4] downloaded from cache at https://opam.ocaml.org/cache
[ocamlfind.1.9.1] downloaded from cache at https://opam.ocaml.org/cache

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
∗ installed ocamlfind.1.9.1
[ERROR] The installation of num failed at "make findlib-install".

#=== ERROR while installing num.1.4 ===========================================#
# context     2.0.6 | linux/x86_64 | ocaml-system.4.10.0 | https://opam.ocaml.org#d9074796
# path        ~/.opam/default/.opam-switch/build/num.1.4
# command     ~/.opam/opam-init/hooks/sandbox.sh install make findlib-install
# exit-code   2
# env-file    ~/.opam/log/num-24962-899ac0.env
# output-file ~/.opam/log/num-24962-899ac0.out
### output ###
# make -C src findlib-install
# make[1]: Entering directory '/home/dev/.opam/default/.opam-switch/build/num.1.4/src'
# sed -e '/\^/d' -e 's/%%VERSION%%/1.4/g' META.in > META
# ocamlfind install num META nums.cma libnums.a big_int.cmi nat.cmi num.cmi ratio.cmi arith_status.cmi big_int.mli nat.mli num.mli ratio.mli arith_status.mli big_int.cmti nat.cmti num.cmti ratio.cmti arith_status.cmti nums.cmxa nums.a int_misc.cmx nat.cmx big_int.cmx arith_flags.cmx ratio.cmx num.cmx arith_status.cmx nums.cmxs dllnums.so
# ocamlfind: Package num is already installed
#  - (file /home/dev/.opam/default/lib/num/META already exists)
# make[1]: *** [Makefile:101: findlib-install] Error 2
# make[1]: Leaving directory '/home/dev/.opam/default/.opam-switch/build/num.1.4/src'
# make: *** [Makefile:18: findlib-install] Error 2



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
┌─ The following actions failed
│ ∗ install num 1.4
└─ 
┌─ The following changes have been performed
│ ∗ install ocamlfind 1.9.1
└─ 

The former state can be restored with:
    opam switch import "/home/dev/.opam/default/.opam-switch/backup/state-20210503221339.export"

[dra27]

I expect you have the num library from your OS package manager installed?

I’m afraid that’s not at present supported by opam-repository (see ocaml/opam-repository#14646). You can either uninstall the OS’s num library and run opam reinstall ocamlfind or create a switch using ocaml-base-compiler.4.10.2 instead of ocaml-system.4.10.0 (this will cause opam to build the compiler from sources instead of using the one installed by your system)

[dra27]

(please feel free to re-open if that diagnosis isn’t correct!)

[wiredsister]

To be honest, it may merit putting this somewhere outside of this closed issue. This exact thing happened to me and I wouldn't have found it otherwise if I hadn't thought to look here. This was a transitive dependency issue for me. Reinstalling ocamlfind fixed for my mac. Thank you @dra27.