According to the documentation of the %{system} variable (https://dune.readthedocs.io/en/stable/concepts.html#variables):

system is the name of the OS the build is targeting. This is the same as ocaml-config:system

However this is not true.
Looking at its definition: https://github.com/ocaml/ocaml/blob/12523517cf5c6c782563f8b76e661b67748e010b/configure.ac#L1044-L1132
on linux for instance, the value can currently be one of:

• linux
• linux_elf
• elf
• linux_eabihf
• linux_eabi

However people only match the first value when used in (enabled_if (= %{system} "linux")) for example.

One possible fix for this would be to match all possible values of system and transform it to a more consistent one (only when (lang dune >= 3.0)):

• linux --> linux
• linux_elf --> linux
• elf --> linux
• linux_eabihf --> linux
• linux_eabi --> linux
• beos --> beos
• bsd_elf --> bsd
• cygwin --> cygwin
• gnu --> gnu
• ....

Or even deprecate the variable all together and invite people to use a new variable (%{os} ?) that has a more involved mapping or even a simple output from uname -s (or uname(3)).

Specifications

• Version of dune (output of dune --version): 2.9.0
• Version of ocaml (output of ocamlc --version): 4.13.0
• Operating system (distribution and version): linux