[Vm-dev] Overview of the OpenSmalltalk VM and its build process

Tue Oct 17 14:00:56 UTC 2017

Hi Raffaello,

Answers inlined...

On Tue, Oct 17, 2017 at 3:07 PM, Raffaello Giulietti <
raffaello.giulietti at lifeware.ch> wrote:

>
> Hi,
>
> I'm interested in understanding the overall OpenSmalltalk VM structure and
> design and its build process.
>
> I read [1] and [2] to get a high level picture of the vm and its
> interesting strategy to development (Slang, VMMaker, etc.)
>
> Apart from these, are there other useful documents/sites/tutorials on the
> vm development process in general and about the underlying ideas in the
> build process? I'm aware that vm construction is a rather special topic but
> any useful reference or hint is welcome.
>
> I'm already familiar with the interesting [3] and [4] websites and their
> authors papers, talks and slides, but these do not seem to help much in
> clarifying the development process itself.
>
> In particular, I'm targeting Pharo 64 bit/Win 64 bit (x64-86). I hope to
> be able someday to actively participate in bringing Cog/Spur/Sista to a
> more mature status on this platform.
>
> The questions I would like to find an answer to are of the following kind:
> * Where should I start?
>

A good start would be to load the Squeak VMMaker dev image (See here:
http://www.mirandabanda.org/cogblog/build-image/) and read the different
opened workspaces. In addition, ...

*Compilation toolchain*

To check you have everything installed to compile, you can go to the one of
the build folder (One of the windows build folder if you're on windows, for
example build.Win64x64, in most case we don't recommend cross compilation),
read the HowToBuild file, then go to one of the inner folder and use the
mvm script to compile a VM from pre-generated C sources.

If it does not work, check on the openSmalltalk-VM repo how the VM is built
using Travis CI and set-up your machine similarly to the Travis slaves.

*Changes in Slang (GC/Interpreter/JIT/...)*

In general when you want to change something in the GC / Interpreter the
process is as follow:

1) Make your changes work with the StackVM (interpreter-only) simulator
2) Make your changes work with the compiled StackVM (interpreter-only)
3) Make your changes work with the CogVM simulator
4) Make your changes work with the compiled CogVM

In general when you want to change something in the JIT the process is as
follow:

1) Make your changes generate correct in-image machine code
2) Make your changes work with the CogVM simulator
3) Make your changes work with the compiled CogVM

So a good place to start is to have the simulators working. You could use
this to help:
https://clementbera.wordpress.com/2016/05/30/simulating-the-cog-vm/

Once the simulator works with your changes, you can generate C sources with
something like "VMMaker generateConfiguration"

*Changes in Platform code*

Go to the platform folder at the root and change the C files with a text
editor

> * Should I use Squaek or can I use Pharo for vm development purposes?
>

Currently I still use Squeak but I plan to migrate to Pharo. I'd say it's
still a bit easier from Squeak due to package compatibility making it hard
to commit from Pharo without uncommitting something else, some scripts are
also present by default in the Squeak dev image, but everything should work
on both environments. No big deal in using one of the other.

> * What are the restrictions of Slang?
>

...
As long as the VM compiles and run, this is correct Slang code, else it's
not.
In general you should just think in C and write Smalltalk instead.
I don't know what to say. This is not dynamic at all. No dictionaries, no
look-up, no nothing. Even arrays look like Smalltalk arrays but like C
arrays you don't have the actual size.
Blocks work as long as they're inlined and removed when performing inlining
in the Slang to C compiler.

* Where does VMMaker live?
>

Half there:
https://github.com/OpenSmalltalk/opensmalltalk-vm
Accessible from git

Half there:
http://source.squeak.org/VMMaker/
Accessible from Monticello

* Which C toolchain shall I use?

* Which release of gcc, ld, make are known to work?
> * What about clang?

Depends on the platform. The mvm script normally chooses for you.

All VMs are built from Travis CI so you can check how to set up your
machine from the Travis set-up.

On linux it's gcc by default. All recent gcc versions should work since 4.4
On Mac, gcc is not supported anymore, so clang is used. I've used many
different versions of clang and they all worked.

Specific compiler versions that don't work are mentioned in the HowToBuild
file in the platform folders (if any).

> * Which version of cygwin64 or mingw64 are OK?
>

Arf. Both worked at some point, I don't know what the default script use
right now I would start with the version used by the mvm script / the
Travis build.

> * etc.
>
>
>
> Greetings
> Raffaello
>
> ---
>
> [1] http://www.vpri.org/pdf/tr1997001_backto.pdf
> [2] http://design.cs.iastate.edu/vmil/2011/papers/p03-miranda.pdf
> [3] http://www.mirandabanda.org/cogblog/
> [4] https://clementbera.wordpress.com/
>

-- 
Clément Béra
Pharo consortium engineer
https://clementbera.wordpress.com/
Bâtiment B 40, avenue Halley 59650 Villeneuve d'Ascq
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