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Date: -- (:)
From: Nicolas Pouillard <nicolas.pouillard@g...>
Subject: Re: [Caml-list] [OSR] Ports-like package management system
Excerpts from Yaron Minsky's message of Wed Jan 30 07:58:15 +0100 2008:
> Jane Street has a setup quite similar to the one Alain describes.  The
> differences are:
> 
>    - We use mercurial instead of SVN
>    - We do most of our building on Linux rather than Windows.
>    - We're less far along the path of bringing external libraries into
>    our tree, and so we still use external package management with GODI and
>    findlib for many of our libraries.  We are moving to a model closer to
>    LexiFi's, though.
> 
> We have a very similar-sounding omake setup, and we have the same feelings
> about the fact that ocamlbuild is not a complete make replacement.

Conceptually  ocamlbuild engine is really a complete make replacement. However
in  surface,  its  quite incomparable since there is no specific language, but
an OCaml API and we write plain ocaml code.

Example of rule written in OCaml for ocamlbuild:

rule "LaTeX to PDF conversion rule"
  ~prod:"%.pdf"
  ~dep:"%.tex"
  begin fun env _build ->
    let tex = env "%.tex" in
    let tags = tags_of_pathname tex++"compile"++"LaTeX"++"pdf" in
    let cmd = Cmd(S[!pdflatex; T tags; P tex; Sh"< /dev/null"]) in
    (* Hoping that \LaTeX will converge in two iterations *)
    Seq[cmd; cmd]
  end;
flag ["compile"; "LaTeX"; "pdf"; "safe"] (A"-halt-on-error");

> On Jan 29, 2008 11:00 AM, Alain Frisch <alain@frisch.fr> wrote:
> 
> > Hello,
> >
> > It's great to see some discussion and thoughts about package management
> > for OCaml software. Of course, various kind of users have different
> > expectations. I'm quite happy with GODI as a package developer or
> > maintainer or when I need to write small applications that uses external
> > OCaml libraries. But I'd like to describe our current approach here at
> > LexiFi concerning the use of external libraries. This is the point of
> > view a company with a few "big" projects, several developers, and
> > several source languages. I guess that many companies that use OCaml
> > would face a similar situation.
> >
> > We develop end-user applications and our main target and development
> > platform is Windows (using the native Win32 and Mingw ports of OCaml),
> > although we also compile everything under Linux. This unfortunately
> > rules out any existing package management system for OCaml. We use a
> > number of third-party libraries in OCaml, C, Fortran that come with
> > source code and some .Net components that come in binary form.
> >
> > We don't want to depend on too many external packages to be downloaded
> > in order to build our projects. Currently, we only rely on a few tools
> > like MS Visual Studio, omake, a Subversion client to be installed on the
> > development machines. Everything else is considered part of our project
> > tree and kept under the control of Subversion. In particular, we have
> > our locally-patched version of OCaml and all the third-party libraries
> > (either in source or binary form) in the repository. (Note that our
> > membership to the Caml Consortium even allow use to redistribute
> > directly this modified version of OCaml.)
> >
> > Putting everything under the control of SVN has several advantages:
> >
> > - the developers don't need to do anything special on their computer
> > when a new library is installed or updated; we know they all have a
> > uniform environment;
> >
> > - it is trivial to add local patches;
> >
> > - we have control over the precise version of the libraries we use (we
> > cannot afford to depend on any external decision to upgrade a library);
> >
> > - in particular, various development branches can have different
> > versions, and it is trivial to go back in time and build an old version
> > with exactly the same libraries as it used to be.
> >
> > The drawback, of course, is that we need to take care manually of
> > upgrading to new versions of external libraries. The OCaml libraries we
> > use are quite stable and we rarely find a serious problem that cannot be
> > resolved by a small local patch. The only project that we follow
> > regularly is OCaml itself. We have a vendor branch in our SVN on which
> > we simply copy a current version from INRIA's public CVS; then we merge
> > the diffs from this vendor branch into our project.
> >
> > Another point worth mentioning is that all our project tree, except the
> > OCaml part, is managed as a single OMake project. Creating OMakefiles
> > for external OCaml/C/Fortan libraries is usually very easy (something
> > like 2-3 lines for each library). It is quite comfortable to be able to
> > patch, add debug statements, etc in 3rd party components and see the
> > changes quickly (without recompiling everything). Another motivation for
> > writing our own OMakefiles is that the Makefiles provided in the
> > upstream packages are often broken under Windows (which is not
> > surprising given how hard it is to deal with Windows path names within a
> > Makefile).
> >
> > We don't use findlib but have recreated a very minimal version of it
> > within omake. Although we haven't done it yet, I can imagine something
> > more serious: omake functions to read findlib's META files (or something
> > similar, maybe in OMake syntax so that they can be simply include'd) so
> > that various parts of the project can declare in a simple way which
> > OCaml libraries they use and that correct flags can be automatically
> > computed and passed to the compilers.
> >
> > We also use omake to do some local configuration (finding where some
> > external tools are, deciding what to compile or not depending on the
> > host system, ...), manage local installation, prepare directory
> > structures to help installer builders and help manage the list of files
> > that should be distributed. We still have some bash/Perl scripts around
> > (using Cygwin under Windows), but we should be able to get rid of them
> > quite easily (omake has its own scripting language). I believe that
> > ocamlbuild is really a great tool but in its current form, it could not
> > replace our use of omake. Since we need something like omake anyway, we
> > don't see a compelling reason to switch to ocamlbuild and to write
> > plugins to compile C#/Fortan/...
> >
> > We are quite satisfied with the current situation. Things could be
> > streamlined if upstream packages came with OMakefiles that could be
> > integrated directly in such configurations (that would require some
> > conventions to be created and followed). It is really a minor point for
> > us, but it could allow to transpose our approach to smaller projects
> > where writing OMakefiles by hand is not desirable. Also, I can imagine
> > that some scripts could automate the task of downloading, integrating
> > and tracking external libraries in a SVN repository, maybe with a nice
> > GUI and a central list of  packages (a la GODI). Note that almost
> > nothing here is really OCaml-specific (except maybe some omake functions
> > / conventions to emulate findlib).
> >
> > -- Alain
> >
> > _______________________________________________
> > Caml-list mailing list. Subscription management:
> > http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> > Archives: http://caml.inria.fr
> > Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> > Bug reports: http://caml.inria.fr/bin/caml-bugs
> >

-- 
Nicolas Pouillard aka Ertai