Transformation of Java Card into Diet Java

1. Semester Project Presentation Transformation of Java Card into Diet Java • Erich Laube <laubee@student.ethz.ch>

2. Overview Introduction to Jive and Background Transformation Basics Examples Future Work Conclusion

3. Jive Java Interactive Verification Environment Code (Java) vs. Specification (JML) Diet Java

4. Goals • Transformation of forbidden constructs. • Reporting errors at compile time for constructs that are not transformed.

5. Involved Tools • ANTLR • parser, lexer • Abstract Syntax Tree (AST) • Multijava • java compiler • static checks, type information • JML • Multijava enhanced with JML

6. Difficulties • Tracking (nested Expressions) • Still knowing where one is • Execution order • Genericity • Constructs forbidden in program but allowed in specification part • large amount of node classes • non-uniform node layout

7. Try-Catch • Only one Catch per Try • done in Grammar file try { // something } catch (Exception1 e1){ // handler1 } catch (Exception2 e2){ // handler2 } try{ try { // something } catch (Exception1 e1){ // handler1 } } catch (Exception2 e2){ // handler2 }

8. Do While => While do { [body] } while (cond) [body] while (cond){ [body] } do { if (x) break; } while (cond) if (x) break; while (cond){ if (x) break; } { boolean b = true while (b){ if (x) break; b = cond; } } { boolean b = true while (b||cond){ if (x) break; b = false }}

9. Constructors • conversion to method: • alter all constructor calls • find them, spread all over the code • call constructor of super method • create default constructor method • but only if no other constructor specified • special case: this() calls • call the initializer method (not always there) • also needs a JML specification

10. Constructor conversion example Class K extends M{ int f; K(int i){ super(i); f = i; } K(){ this(2); } } Class K extends M{ int f = 2; K(int i){ super(i); f = i; } K(){ this(f); } } Class K extends M{ int f; void °cK(int i){ super.°cM(i); f = i; } void °cK(){ °cK(2); } } Class K extends M{ int f; °inst_init(){ f = 2; } void °cK(int i){ °inst_init(); super.°cM(i); f = i; } void °cK(){ °inst_init(); °cK(f); } } Class K extends M{ int f; boolean °init; void°inst_init(){ if (°init){} else { f = 2; °init = true; }} void °cK(int i){ super.°cM(i); °inst_init(); f = i;} void °cK(){ °inst_init(); °cK(f); } }

11. Future Work • Remaining Transformations • non-strict operators • pre- and postfix operators (++,--) • inner classes • Optimizations: • reuse temporary variables • simple trafos for simple cases

12. Conclusion • Many constructs covered • Mangled code: • difficult for user to still understand • Interesting and complex project

13. Implemented Transformations • constructors • nonstatic initializers • variable initializers • local variables only at beginning of blocks • short if, for and do-loops, switch-blocks • multiple catch blocks for a try-block • casts within expressions • array access within expressions • compound assignment • assignment within expressions • assignments with side effects (partially) • pre- and postfix operators (partially)

14. Questions...?

15. Grammar File (ANTLR) • Passes every code construct • No Type Information • Also affects JML part • Work done here: • finding and forbidding • types • simple transformations • If-then-else • Try-catch

16. Abstract Syntax Tree (Multijava) • Statements • can hold more Statements • can hold Expressions • Expressions • never hold Statements • can hold further Expressions