[Vm-dev] Fwd: Nix package for Pharo flavor of opensmalltalk-vm

Tue Apr 18 16:59:21 UTC 2017

On Tue, Apr 18, 2017 at 4:13 AM, Luke Gorrie <luke at snabb.co> wrote:
>
>
> Hoi,
>
> Just summarizing the "Pharo 6 snap install" thread from -users and -dev
list,
>
> I made a nix package for the latest (git master) Pharo VM with much help
from the mailing list.

btw, just to clarify, the "master" branch of
https://github.com/pharo-project/pharo-vm
is synchronised to the "Cog" branch of
https://github.com/OpenSmalltalk/opensmalltalk-vm

>
> If you first install nix:
>     curl https://nixos.org/nix/install | sh
>
> Then it's easy to install the package from my development branch:
>     nix-env -f https://github.com/lukego/nixpkgs/archive/pharo6.tar.gz
-iA pkgs.pharo-vm
>
> and then you can run it with pharo-vm-x (or pharo-vm-nox for headless.)

This worked fine for me on 32bit Debian 8 Jessie, resulting in...
  $ pharo-vm-x  -version
5.0-git.1c38b03fb043a2962f30f080db5b1292b5b7badb  Tue Apr 18 16:46:48 UTC
2017 gcc 6.3.0 [Production Spur VM]
CoInterpreter VMMaker.oscog-eem.2188 uuid:
ff4ca601-cd05-4792-ab0d-dcdf19975239 Jan  1 1970
StackToRegisterMappingCogit VMMaker.oscog-eem.2188 uuid:
ff4ca601-cd05-4792-ab0d-dcdf19975239 Jan  1 1970
VM: git.1c38b03fb043a2962f30f080db5b1292b5b7badb
https://github.com/pharo-project/pharo-vm $ Date: Wed Apr 12 19:25:16 2017
+0200 $
Plugins:
Linux dom0 3.16.0-4-686-pae #1 SMP Debian 3.16.7-ckt25-2 (2016-04-08) i686
GNU/Linux
plugin path: /nix/store/w7hp77nli2khxvwp2dx3sbm6a3z4drlp-pharo-vm/lib/
[default: /nix/store/w7hp77nli2khxvwp2dx3sbm6a3z4drlp-pharo-vm/lib/]

>
> Nix is a bit special. It will make a deep copy of all the dependencies
including libcairo, glibc, etc. This means that it really should work the
same on your computer as on mine, and it should also work the same if you
run that command 5 years from now. (Like a cross between apt-get and
docker.) The dependencies and be updated and debugged in a disciplined way
(see example cute trick.)
> https://github.com/lukego/blog/issues/17

Thats quite amazing to be able to bisect the compiler tool chain
dependencies across OS versions like that.

>
>
> Here is the source for the build script:
>
https://github.com/lukego/nixpkgs/blob/pharo6/pkgs/development/pharo/vm/build-vm.nix

How the parameters are provided is also interesting...
https://github.com/lukego/nixpkgs/blob/pharo6/pkgs/development/pharo/vm/default.nix

>
> This is based on the mvm script for Pharo. On the one hand it's simpler
because nix takes care of all the third-party dependencies automatically,
but on the other hand it's complicated because nix builds have to be
referentially transparent and can't use curl, whoami, date, git, etc. There
are also potentially many versions of each program installed on the machine
and so you can't use global names like /bin/rm but rather have to rely on
$PATH to give you the right one.
>
> So I made some straightforward adaptations to accommodate nix, and also
e.g. to avoid building with gcc5 which crashes during compilation.
>
> My script is based on work by Damien Cassou who packaged an earlier
version of the VM and has since moved on to other projects. I picked up the
maintainership from him and will send this package to nix upstream once I
test it a little better.

I had seen Damien mention nix before, but I didn't realise it covered
reproducibility of the whole build environment so completely.

>
>
> Why bother packaging the Pharo VM with nix? There are a few reasons for
me. I already run NixOS and the Pharo binaries don't work there. Building
from source takes more work than 'configure && make install' so it's worth
automating. I'm not comfortable with the zeroconf installers because they
feel opaque and I am never quite sure what software I am running on each
machine. And I want to build a large application including Pharo + many
other components and I need a tool to keep me out of dependency hell.

> More on Nix: gentle introduction
> https://www.infoq.com/articles/configuration-management-with-nix

This seems like useful tech for on-boarding new developers in a
geographically dispersed team, "A Nix expression can serve as a declarative
specification of all the dependencies that your project needs. Nix can then
automatically build or download these dependencies in the exact versions
required by your project, freeing developers from having to do this
manually."

Being able to try a compiler upgrade and then cleanly rollback is a great
feature.  I gather that under the covers, so switching between two
environments is just a quick link change?

Having the package hash based on "the source code of the package and the
build script, [and] also dependencies such as the C compiler and libraries
against which [it] links (such as OpenSSL)" seems a really strong approach
to configuration management and reproducibility of historical build
environments.  As well as being great for production environments I could
imagine a newcomer reporting "I'm having trouble building, here is my nix
configuration" and an expert could use `nix-shell` to build within an
identical environment to avoid the "works for me" phenomenon of hidden
dependencies.

> This is the best new technology that I have stumbled upon in the past
couple of years.

The world turns.  Thanks for the heads up.

Now would any of the other dialects like to add to this?
At a minimum, perhaps just adding sources filesto...
https://github.com/lukego/nixpkgs/blob/pharo6/pkgs/development/pharo/vm/share.nix

cheers -ben
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