Mission Pharo Kernel Video: https://youtu.be/YQD0pSb2mzw Thu, August 25, 10:00am – 10:30am First Name: Guillermo Last Name: Polito Email: guillermopolito@gmail.com Title: Mission Pharo Kernel Type: Talk Abstract: The Pharo team and community have been working a lot lately to make Pharo a modular system. The mission: make Pharo a simpler system, easier to build and change. The tools: dependency analyses, refactorings, bootstrapping, modular package installation. The challenges: a circular system definition, spaghetti and legacy code, hidden dependencies. This talk presents the work around the Pharo Kernel, a minimal Pharo image that contains the necessary systems to boot and load your own packages. The Pharo Kernel is not only an image. It is also a new process to build an image. A new process to manage, validate and install packages in Pharo, to integrate issues, to build Pharo systems. In this talk you'll learn what you could expect from Pharo in the (not so far away) future. Bio: Guille Polito is research engineer at CNRS, France. Pharoer since 2010, he participates actively in the Pharo open source community since several years. He currently works on the modularization of Pharo where he does software archeology, refactoring, library rewriting and participates in the Virtual Machine development.

1. Mission Pharo Kernel
ESUG 2016, Prague
Pavel Krivanek and Christophe Demarey

2. New libraries
New tools
New tests
More documentation
Pharo is growing

3. Pharo evolution
Squeak 3.9 Pharo 1.0 Pharo 1.1 Pharo 1.2 Pharo 1.3 Pharo 1.4 Pharo 2.0 Pharo 3.0 Pharo 4.0 Pharo 5.0
Classes
Packages
LOC

4. Code for future use
Duplicities
Obsolete code
DO-NOT-TOUCH code

6. Pharo ZEN
● Easy to understand, easy to learn from, easy to change.
● Objects all the way down.
● Examples to learn from.
● Fully dynamic and malleable.
● Beauty in the code, beauty in the comments.
● Simplicity is the ultimate elegance.
● Better a set of small polymorphic classes than a large ugly one.
● Classes structure our vocabulary.
● Messages are our vocabulary.
● Polymorphism is our esperanto.
● Abstraction and composition are our friends.
● Tests are important but can be changed.
● Explicit is better than implicit.
● Magic only at the right place.
● One step at a time.
● There is no unimportant fix.
● Learning from mistakes.
● Perfection can kill movement.
● Quality is a emerging property.
● Simple processes to support progress.
● Communication is key.
● A system with robust abstractions
that a single person can understand.

7. Modularity

8. Pharo Kernel

9. From top
- cleaning
- shrinking
- reloading
From bottom
bootstrapping from zero -
reloading -

10. From top shrinking and modularization
- started before Pharo
- removing of code is easy
- clean removing is not easy
- reloading is even harder
Morphic reloaded [22.07.2006]

11. Kernel image evolution in shortcut
BROKEN!
works again
BROKEN!
works again
BROKEN!
works again
BROKEN!
works again
BROKEN!
works again
BROKEN!
works again
BROKEN!
works again
Broken again... [18.8.2016]

12. Why so hard and long?
Everyone needs to
take of care of
modularity
integrated inintegrated in
development processdevelopment process
(tests, rules, CI jobs)(tests, rules, CI jobs)

13. CI jobs for Pharo modularization
- since Pharo 2.0
- shrink image
- increase granularity of reloaded modules
- tests
- coverage testing
- experiments (Tanker)
https://ci.inria.fr/pharo/view/6.0-SysConf/

14. CI jobs for Pharo modularization
Kernel image (shrinked / bootstrapped)
+ Monticello
+ Network support
+ Remote repositories support
+ Metacello
= minimal Pharo
+ SUnit, Display support, UFFI
+ Morphic core, Morphic
+ UI, Basic tools, IDE
= Pharo

15. Bootstrapped & reloaded from GIT

16. Let's talk about
BOOTSTRAP

17. « The process that builds the minimal
infrastructure of a langage reusable to define the
langage itself »
Bootstrap

18. Why do we need a bootstrap ?
● Have a known initial state
● Be able to reproduce the state of a system
● Ensure we can reinitialize the system at any time
● Ease Kernel evolution
● Identify a small subset of the language allowing
the definition of the language itself

19. Why bootstraping is difficult?

20. Archaelogy

22. Dead code!

23. Strange things

24. cleanups

25. Missing code

26. The dependency hell

27. Cut dependencies

28. Code refactoring

29. How to fix bad dependencies?
Create a new package to isolate functionnalities
Move some methods as extensions to another
package
Re-design completely a functionality
e.g. startup list
...

30. Tools support

31. Dependency Analyser

32. Dependency dashboard
X 2

33. Dependency visualization
https://ci.inria.fr/pharo/job/Pharo-6.0-Dependenc
yAnalysis/ws/bootstrap-dependency-report-graph.ht
ml

34. The bootstrap process

36. 1
Day

38. 2
Day

39. 3
Day

40. 4
Day

41. 5
Day
process

42. 6
Day

43. 7
Day

44. More details
cf phd Guillermo Polito:
https://hal.inria.fr/tel-01251173

45. Story #2

46. Road to a working bootstrap

47. Bootstrap challenge
> language side bootstrap
Language initialization generally done VM side
We want to do it language side (image side):
need to run code on top of a language under
construction

48. Bootstrap challenge
> language side bootstrap

49. Road to a working bootstrap
First bootstrapped image!

50. Road to a working bootstrap

51. Road to a working bootstrap
We run the image …
… VM crash

52. Road to a working bootstrap
> some debugging examples
Missing class in the boostrap
e.g. Float
Super class not set
Super class set to a wrong value

53. Road to a working bootstrap
Compile VM in debug mode
Run bootstrapped
image through
Xcode / LLDB

54. Road to a working bootstrap
> verifying the bootstrap
Rely on Pharo tests (>8 000 tests)
● Load SUnit
● Load test packages
● Run tests

55. Wants to know more?
Bootstrap process hosted on Pharo CI server
https://ci.inria.fr/pharo/view/Pharo%20bootstrap/
GitHub repository
https://github.com/guillep/PharoBootstrap

56. Conclusion
Having a modular system requires a lot of energy
• Easy to break
• Concern of everyone
We now have a working Pharo bootstrapped
image.
We are able to load packages on top to build a full
Pharo-image (UI, IDE, etc.)

57. Roadmap
Make the boostrap process more robust
Up-to-date package dependencies for the Pharo
image + use of Cargo package manager
Build the official Pharo image on top of the
bootstrap
Make the kernel smaller (e.g. kick out Unicode)

58. « Always leave the campground
cleaner than you found it. »
-Boy Scout rule, Uncle Bob