Currently, in OCaml code in the wild, people use the output of ocamlc -config to detect the architecture and OS of the system they are on.

However while debugging janestreet/core#145 I discovered that the variable system, in particular, is not consistent and does not always return "linux" on linux systems for example.

This pattern of using the system variable to detect the OS is especially prevalent in dune where there is no other builtin way to get this information (see ocaml/dune#4895).

In addition of fixing dune and other build systems with similar issues (I believe oasis, back in the days, also used the system variable: https://github.com/ocaml/oasis/blob/master/setup.ml#L4133), I think it would be nice to make the variable more consistent. e.g.

• regroup all the linux variants as linux
• regroup bsd_elf and bsd as bsd
• regroup all the openbsd variants as openbsd (currently it's split between bsd and openbsd depending on the architecture)
• regroup win32 and win64 into one (not sure which name it should have, but having the system variable carry the same information as the architecture variable doesn't seem right to me)
• same for mingw and mingw64 (cc @dra27 who probably has ideas about windows)

See

for the list of current possible values of system