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K Framework

K Framework. k-framework.org. Joint project between the FSL group at UIUC (USA) and the FMSE group at UAIC (Romania). K Team. UAIC, Iasi, Romania Dorel Lucanu Traian Serbanuta Andrei Arusoae Denis Bogdanas Stefan Ciobaca Gheorghe Grigoras Radu Mereuta

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K Framework

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  1. K Framework k-framework.org Joint project between the FSL group at UIUC (USA) and the FMSE group at UAIC (Romania)

  2. K Team • UAIC, Iasi, Romania • Dorel Lucanu • TraianSerbanuta • Andrei Arusoae • Denis Bogdanas • Stefan Ciobaca • Gheorghe Grigoras • RaduMereuta • RalucaNecula • EmilianNecula Former Members • Irina Asavoae • MihaiAsavoae • UIUC, USA • GrigoreRosu (started K in 2003) • CansuErdogan • Dwight Guth • David Lazar • Patrick Meredith • Andrei Stefanescu Former members • Kyle Blocher • Peter Dinges • Chucky Ellison • Mike Ilseman • TraianSerbanuta

  3. Current State-of-the-Art in PL Design, Implementation and Analysis Consider some programming language, L • Formal semantics of L? • Typically skipped: considered expensive and useless • Implementations for L • Based on some adhocunderstanding of what L is • Model checkers for L • Based on some adhoc encodings/models of L • Program verifiers for L • Based on some other adhoc encodings/models of L • …

  4. Example of C Program • What should the following program evaluate to? • According to the C “standard”, it is undefined • GCC4, MSVC: it returns 4GCC3, ICC, Clang: it returns 3By April 2011, both Frama-C (with its Jessie verification plugin) and Havoc "prove" it returns 4 int main(void) {int x = 0; return (x = 1) + (x = 2);}

  5. A Formal Semantics Manifesto • Programming languages must have formal semantics!(period) • And analysis/verification tools should build on them • Otherwise they are adhoc and likely wrong • Informal manuals are not sufficient • Manuals typically have a formal syntax of the language (in an appendix) • Why not a formal semantics appendix as well?

  6. Motivation and Goal We want a semantic framework which makes it easy and fun to define programming languages, no matter how complex or large they are!

  7. The K Frameworkk-framework.org A tool-supported rewrite-based framework for defining programming language design and semantics.

  8. Complete K Definition of KernelC

  9. Complete K Definition of KernelC Syntax declared using annotated BNF …

  10. Complete K Definition of KernelC Configuration given as a nested cell structure. Leaves can be sets, multisets, lists, maps, or syntax

  11. Complete K Definition of KernelC Semantic rules given contextually <k> X = V => V …</k> <env>… X |-> (_ => V) …</env>

  12. What does the K Tool Offer? … … cfg[pgm] … Efficient and interactive execution (interpreters) State-space exploration (search and model-checking) Deductive program verification (in progress)

  13. K Scales Besides smaller and paradigmatic teaching languages, several larger languages were defined • Java 1.4 : by Chen [CAV’06] • Verilog : by Meredith&Katelman[MEMOCODE’10] • C : by Chucky Ellison [POPL’12] etc.

  14. The K Configuration of C Heap 75 Cells!

  15. Statistics for the C definition • Total number of rules:   ~1200 • Tested on thousands of C programs (several benchmarks, including the gcc torture test, code from the obfuscated C competition, etc.) • Passed 99.2% so far! • GCC 4.1.2 passes 99%, ICC 99.4%, Clang 98.3% (no opt.) • The most complete formal C semantics

  16. Next Steps for Learning • Watch the five-minute video demo • Download the K tool • Do the K Tutorial • Define your own language! • Watch the interview on rewrite-based semantics if you’d like to better understand our viewpoint • Read select publications for a deeper understanding of K’s foundations

  17. Part 2 • History • Technicalities (parsers) • Basic parsing • Concrete parsing • Disambiguation

  18. History • K2 • Maude, Perl, Haskell, Java • K3 • SDF for parsing • Java for tools • Maude for execution

  19. Technicalities • Parsers • Basic parser • Modules • Syntax • Sentences with concrete syntax (rules, configurations) • Concrete parser (finish the above)* • Parser for programs* *generated during compilation

  20. Basic parsing module EXAMPLE syntax Exp ::= Exp “*” Exp [left, strict] > Exp “+” Exp [left, strict] configuration <T> <k> 1 + 2 * 3 </k> </T> rule E1:Int + E2:Int => E1 +Int E2 …. endmodule

  21. Basic parsing module EXAMPLE syntax Exp ::= Exp “*” Exp [left, strict] > Exp “+” Exp [left, strict] configuration<T><k>1+2*3</k></T> ruleE1:Int+E2:Int=>E1+IntE2 …. endmodule

  22. Concrete parser • K syntax • K “=>” K -> K • <cell> Content </cell> • Language syntax • Exp “+” Exp -> Exp … • Connections • Exp -> K > K -> Exp and K -> Exp > Exp -> K • Typed variables

  23. Disambiguation • Cell disambiguation • Variable type inference • Second type checker • Report the rest of ambiguities

  24. Rest of the compilation • Syntax flattening • Context transformation • …

  25. Krun (runtime) PGM <T> <k> $PGM </k> <env> a |-> 1 </env> </T>

  26. Future work • Right now • Bug hunting • Performance improvements • Long term • Finish the java version of the compilation • IDE • Specialized rewrite system

  27. Next Steps • Watch the five-minute video demo • Download the K tool • Do the K Tutorial • Define your own language! • Watch the interview on rewrite-based semantics if you’d like to better understand our viewpoint • Read select publications for a deeper understanding of K’s foundations

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