This is a bug, but I think it is likely to be coming from a
misconfiguration on your end: the preinstalled test checks
  $(ocamlc -where)/ocamlbuild
and if you are in a non-system switch this should not be
/usr/local/lib/ocaml.

Did you correctly run

  eval $(opam config en)

after switching?

On Sat, Jun 25, 2016 at 9:57 AM, Soegtrop, Michael <
michael.soegtrop@intel.com> wrote:

> Dear OCaml Users,
>
>
>
> Opam works fine for me with the system installed OCaml, but after an opam
> switch I cannot build ocamlbuild or any package depending on it any more.
>
>
>
> Building ocamlbuild fails because it explicitly checks if there is already
> a system installed ocamlbuild:
>
>
>
> # ERROR: Preinstalled ocamlbuild detected at
> /usr/local/lib/ocaml/ocamlbuild
>
> # Installation aborted; if you want to bypass this safety check, pass
> CHECK_IF_PREINSTALLED=false to make
>
> # make: *** [Makefile:333: check-if-preinstalled] Error 2
>
>
>
> Of cause I can just follow this advice and remove this check, but I wonder
> how others handle this.
>
>
>
> Best regards,
>
>
>
> Michael
>
>
>
> Intel Deutschland GmbH
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