Masters Project

1
Masters Project

• Extraction of State Machine Diagrams of
• Legacy C code with Cpp2XMI
• Vanderlande Industries B.V. (Veghel)
• Dennie van Zeelandd.h.a.v.zeeland_at_student.tue.nl

2
Outline

• Introduction
• Project goal
• Related work
• Tools
• State Machine patterns
• Switch-Case / Switch-Case pattern
• Overview of design of Cpp2XMI
• CPPML
• Case Study - FSC
• Problems encoutered
• Conclusions / Future work

3
Introduction

• Vanderlande Industries (VI)
• Automated material handling systems
• distribution centres
• baggage handling at airports
• express parcel sortation facilities
• Flow System Controller (FSC)
• Controls the product flows in conveyor systems
  for transport and sortation
• Controls all motors, photocells and other active
  components
• Send and receive control and status information
• Realtime control of equipment
• Separated GUI
• Standard interfaces with equipment
• Fully configurable for all VI sorting equipment

4
Project goal

• Reverse Engineering documentation from C/C
  source code
• Why
• Limited documentation available for V5/V6
• State machine diagrams
• Identifying possible flaws in current versions
• V7 is being developed from scratch
• Extracting dynamic behavior from source code for
  V7
• Identifying requirements
• Building a tool for extracting state machine
  diagrams from code
• Preprocessing source code
• Parsing source code
• Finding patterns in source code of state machines
• Creating diagrams

5
Related work

• ESPaRT KNOR98
• Finding state machine patterns and replacing them
  by better constructs
• Bandera CORB00
• Extract state machines and produce input for
  model checkers
• Symbolic Execution WALK08
• Program conditioning
• Brastra YUAN06
• Extracting state machines using unit tests
• Log based state machine extraction GANN06

6
Tools

• Cpp2XMI
• Developed by Elena Korshunova for LaQuSo
• C to UML-diagrams
• Class diagram
• Sequence diagram
• Activity diagram
• Columbus/CAN toolset
• Pre-processor Parser Linker
• Static analyser (Class diagram extraction)
• CPPML (C Markup Language)
• Use Cpp2XMI as basis and extend it with
• State machine diagram

7
State Machine Patterns

• Global type of patterns for implementing state
  machines
• Nested Choice Patterns
• Switch/Case Switch/Case pattern (mainly used in
  FSC)
• Switch/Case If/Else
• If/Else Switch/Case
• If/Else If/Else
• Jump Tables
• Pointer to a function pointer array represents
  state variable
• Function pointer array is the jumb table
• Table contains the event handler functions
• Object oriented approach
• States as classes
• Goto statements
• Use goto statements to jump through program
• Each goto statement corresponds to a state
  transition

8
Switch/Case Switch/Case pattern (1)

• States

9
Switch/Case Switch/Case pattern (2)

• Transitions

10
Switch/Case Switch/Case pattern (3)

• Object with current state variable

11
Switch/Case Switch/Case pattern (4)

• Control Function

12
Switch/Case Switch/Case pattern (5)

• Multiple events with the same event-handler

13
Switch/Case Switch/Case pattern (6)

• State assignment in called function

14
Switch/Case Switch/Case pattern (7)

• Conditional transitions

15
Overview of design of Cpp2XMI (1)
Abstract Syntax Tree in XML-format
Class Diagram in XML (XMI)-format
Class, Sequence, Activity Diagram in XML
(XMI)-format
16
Overview of design of Cpp2XMI (2)
X
Could be improved
17
Case Study - FSC (1)

• Applied Cpp2XMI to FSC V6

18
Case Study - FSC (2)

• Example SPUR

19
Case Study - FSC (3)

• Example Triplesorter

20
Case Study (4)

• Some results of the Cpp2XMI State Machine Diagram
  Extractor
• V6 27 State Machine Diagrams, 2 false positives
• Extracted state machine is for 70 identical to
  original documented state machine (Gappex)
• Correctness was checked and confirmed by domain
  experts

21
Problems encountered

• Preprocessing issues
• Columbus Parser doesnt understand anonymous
  structs/enums
• Sax parser issues
• Sax parser halts on the escape character (0x1B)
• CPPML should have a tree-structure (1 on 1 with
  AST)
• However its a DAG, which makes pattern
  recognition is tricky
• Cpp2XMI doesnt extract control-statements (do,
  while, if, switch break, continue, etc.)
  correctly (for C)
• Performance issues with CPPML parser
• JDOM (Memory peak level 1,8GB)
• SAX (will not solve memory peaks)
• Bug in XMI-part
• Duplicate ids, which raises errors when
  importing XMI into case-tools (Enterprise
  Architect)
• Position information not part of XMI
• Enterprise Architect doesnt do anything with
  position information

22
Conclusions / Future work

• Conclusions
• UML state machines are useful for the developers
  and maintainers
• Can be derived automatically from source code (by
  finding patterns)
• Was very successful in the case study and is in
  general promising
• Future work
• Expanding the state machine patterns
• Combine with logging to get a general state
  machine
• Export function for model checkers
• On Entry / On Exit
• Metrics / analysis over overlap of state machine
  diagrams
• Filter / Zoom
• Use original CPPML parser
• XMI conversion
• Improve performance issues (due to choice of
  parser)

23
Questions?
24
References (1)

• KNOR98
• Roland Knor, Georg Trausmuth and Johannes Weidl
• Reengineering C/C Source Code by Transforming
  State Machines
• Proceedings of the Second International ESPRIT
  ARES Workshop on Development and Evolution of
  Software Architectures for Product Families
• 1998
• ISBN 3-540-64916-6, Page 97105
• Springer-Verlag
• CORB00
• James C. Corbett, et al.
• Bandera extracting finite-state models from Java
  source code
• Proceedings of the 22nd international conference
  on Software engineering,
• 2000
• ISBN 1-58113-206-9, Page 439448
• ACM
• WALK08
• Neil Walkinshaw et al.
• Automated discovery of state transitions and
  their functions in source code
• Journal Software Testing Verification
  Reliability (Vol 18, nr 2)
• 2008

25
References (2)

• YUAN06
• Tao Xie and Evan Martin and Hai Yuan
• Automatic extraction of abstract-object-state
  machines from unit-test executions
• Proceedings of the 28th international conference
  on Software engineering
• 2006
• ISBN 1-59593-375-1, Page 835838
• ACM
• GANN02
• Gerald C. Gannod and Shilpa Murthy
• Using Log Files to Reconstruct State-Based
  Software Architectures
• Workshop on Software Architecture Reconstruction
  at WCRE 2002
• 2002
• FERE02
• Rudolf Ferenc et al.
• Columbus - Reverse Engineering Tool and Schema
  for C
• Proceedings of the International Conference on
  Software Maintenance
• 2002
• ISBN 0-7695-1819-2, Page 172
• IEEE Computer Society