Upgrade OCaml compiler in default opam switch

Learning
1

I’d like to upgrade the compiler version in my default opam switch to 4.12.0. I’m very new to OCaml, so I’m not even sure if this is a “normal” thing to do. The switch says it’s using compiler ocaml-system.4.10.0. I can see the latest version of this library is ocaml-system.4.12.0 on opam but when I opam update and opam upgrade ocaml-system it says there is nothing to do. When I run opam upgrade ocaml-system.4.12.0 I get an explicit error of:

[ERROR] ocaml-system = 4.12.0 unmet availability conditions: sys-ocaml-version = "4.12.0"

which seems to contradict what I see above on opam.

I have a feeling I’m going about this incorrectly, but I couldn’t find any explicit docs on upgrading the compiler, so any tips on how to correctly do this would be appreciated!

2

The system compiler is the one installed by a package manager (such as apt on debian) on your system. You can’t upgrade it using opam. In your case, I think that instead you should create a new switch with your desired ocaml version.

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3

Thank you, that’s nice to know. I’ve done what you suggest with opam switch create 4.12.0. Is there anything I should do to make that the “default” switch? Or can I just do an opam switch set 4.12.0 and then continue?

4

Yep and do eval (opam env) (fish shell) or bash eval `opam env` in bash.

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5

default is a name like any other, it has no special meaning in opam (as far as I know). So there’s no particular reason to name a new switch default. I’d probably even advertise against doing it. But if you ever wanted to do it, it’s pretty simple

opam sw remove default # note that it won't remove the ocaml install on your system, just the opam switch
opam sw create default 4.12.0
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