Bug#878291: libllvm-5.0-ocaml-dev: Please consider dropping ocaml bindings or moving to a separate source package

[Simon McVittie]

Package: libllvm-5.0-ocaml-dev
Version: 1:5.0-3
Severity: wishlist

The ocaml bindings for LLVM cause it to be entangled in the ongoing
ocaml transition, which happens often enough that it has a permanent
transition tracker. ocaml ABI compatibility appears to be based on
lockstep upgrades involving a hash of the compiler, which seems prone
to frequent transitions; the transition tracker currently reports 90
source packages in 20 dependency levels, which take a while to work
through.

This causes buildability and installability issues for LLVM itself
(#876752) and for packages that depend on it, notably Mesa. It seems
a shame for bindings for ocaml (highest popcon among binary packages:
5737) to be holding back testing of new versions of Mesa (highest popcon:
135549) and clang (6643).

According to dak, nothing in Debian actually depends or build-depends
on any of the ocaml bindings for the LLVM family, as demonstrated by
there being no dependency problem if all those binary packages were to
be removed:

    smcv at coccia ~ % dak rm -R -n -b libllvm-{3.7,3.8,3,9,4.0,5.0}-ocaml-dev libllvm-ocaml-dev
    ...
    Checking reverse dependencies...
    No dependency problem found.

and the bindings themselves have a correspondingly low popcon score,
with 17 known installations of the most popular branch
(libllvm-3.8-ocaml-dev).

Based on that, it seems like it might be worth considering either
removing the ocaml bindings, or breaking them out into a separate
source package so that they don't have to hold up LLVM itself.

Thanks,
    smcv