Bug#1125673: ghc: Please do not ship files under /var

[Stéphane Glondu]

Le 17/04/2026 à 15:13, Gioele Barabucci a écrit :
>>>> >1105 Haskell packages (all Haskell packages?) install one or more 
>>>> >files in /var/lib/ghc/package.conf.d/.
>>>> >
>>>> >Would it be possible to change the way these packages are built, so 
>>>> >that they do not ship any files under /var, a directory meant to 
>>>> >"[contain] _variable_ data files" (FHS)?
>>>>
>>>> Kari, can you give us some insight about why they were moved to
>>>> /var in the first place?
>>>
>>>  From conversations in IRC it seems that it would be easy to move 
>>> these files away from /var, but what is missing is to understand 
>>> (Chesterton's Fence-like) for which historical reasons these files 
>>> are installed there.
>>
>> I guess the same applies to OCaml packages... And (as far as OCaml is 
>> concerned), I am partly responsible.
> 
> Should I open a new bug for OCaml and add there some OCaml-specific data?

After an exchange with my coauthors (and thinking), /var/lib/dpkg/info 
might have been an inspiration for the choice of /var/lib/ocaml in the 
first place...

> Or do you (Haskell and OCaml dev) think that is makes more sense to try 
> to seek a common solution (location, at least) for both languages?

It may.

/var/lib/ocaml currently contains static data, computed at build time 
over build artifacts, that are used to easy the work of dh_ocaml (and 
lintian). It is similar in spirit to dune-package files that exist 
outside Debian (and are installed in /usr/lib).

What would be the canonical location for that? I'm thinking about 
"$(ocamlc -where)/.dh-ocaml" (aka "/usr/lib/$arch/ocaml/.dh-ocaml"), or 
spreading each package's data in each package's dir in /usr/lib, e.g. 
"$(ocamlc -where)/$pkg/.dh-ocaml". Any opinions?

> Truth be told, the kind of information that OCaml packages store in `/ 
> var/lib/ocaml/` strikes me as very different from what Haskell/GHC 
> packages store in `/var/lib/ghc/package.conf.d/`. But I'm just a 
> bystander. :)

I just had a look. Actually, the data in /var/lib/ghc/package.conf.d 
makes me think of dune-package files (which are built by upstream 
toolchain, but not everyone uses dune).

All in all, in OCaml world, the difference between /usr/lib and /var/lib 
is: /usr/lib is built by upstream toolchain, and /var/lib is built by 
Debian toolchain. The distinction made sense back at the time, but I'm 
no longer convinced now.

Any thoughts?


Cheers,

-- 
Stéphane