Lately, certain OCaml programs stopped working properly with an `unknown C primitive` error.

The concrete message was:

Fatal error: unknown C primitive `caml_ba_dim_1'

after I used OPAM to install a new version of the OCaml compiler.

Sometimes it worked, and sometimes it didn't which finally lead to a problem with environment variables. I found the following situation: In ~/.opam/opam-init/variables.sh, the environment variable CAML_LD_LIBRARY_PATH was set to both the OPAM-related path ~/.opam/4.01.0/lib/stublibs and the system installed compiler's stublibs as well /usr/local/lib/ocaml/stublibs. After I removed the latter, everything worked fine.

See bug reports for Utop as well as for batteries-included.