automated fixing of programs with contracts.pptx

8/17/2019 Automated Fixing of Programs with Contracts.pptx

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MIDHUN

MOHAN S7

ROLL NO

Automated Fixing of Programswith ontra!ts

"


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OUTLINE

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IntroductionBackgroundPreliminariesHow Auto Fix WorksExperimental results.Coclusion


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INTRODUCTION

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A programmer always faces two c allenges !.Finding faults ".Correcting t em

• %Is a tec ni#ue and supportingtool

• t t at can generate correction forfaults faults of general purposesoftware

• completely automatically.

What isAutofix


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A$%&FI' I( AC%I&(..

A dou)ly*linked list implementing %W&+WA,+-& %E/+-E% &

'


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-ome features of class %W&+WA,+-& %E/+-E% &

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Continues0

)


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Correction of t e error in 1mo2e+item3automatically generated )y AutoFix &

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P E4I5I(A IE-

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Contracts


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How Auto Fix Works666

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",

Auto Fix starts wit a set of test cases t at expose a specific f


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Candidate fixes...

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collection of predicates t at all old at passing in2ariant *>Failing in2ariant

Passing In2ariant 7 8? l:7Collection of predicates t at oldin all passing test.Failing In2ariant 78@ l:7 collection of predicates t at old in allfailing tests .

In2ariant Analysis


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Fault 4ocali ation

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% e goal of t e fault locali ation p ase is todetermine w ic snaps ots in snap8%: are relia)lec aracteri ations of t e reasons for t e faultunder analysis

% e static analysis performed )y

Auto Fix is )ased on simple measures of proximityand similarity

Control dependence

Expression dependence

-tatic Analysis


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C&(% &4

/EPE(/E(CE E'P E--I&(

/EPE(/E(CE

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Auto Fix uses controldependence torank locations 8insnaps ots: according toproximity to t e

location of failure .

Auto Fix usesexpressiondependence to rankexpressions 8insnaps ots: accordingto similarity to t econtract clause2iolated in a failure


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"7

It is used to determine w ic locations are likely to ost t e cause

of failure.• /ynamic score dyn 8l9p92: measure ow often it appears in failing runs

as opposed to passing runs.

• Principle for computing t e dynamic score7 li 8l9p92: t if li loc 8t:9 l;li and 2;Dp

t•

For e2ery test t9 t ere is 8t: descri)es t=s contri)ution to t edynamic score8l9p92:.

• 4arge 8t: implies 8l9p92: is a source of error if t is a failing testcases.

/ynamic Analysis


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meets t e following re#uirements

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If t ere is at least onefailing test case9t e o2erall score

assigned to8l9p92:must)e positi2e

% e magnitude of eacfailing test case=s

contri)ution 8t: to t edynamic score assigned

to8l9p92:decreases asmore failing test casesfor t at snap s ots are

a2aila)le

% e e2idencepro2ided )y onefailing test casealone is stronger

t an t e e2idencepro2ided )y onepassing test case


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AutoFix com)ines t e2arious metrics8staticand dynamic: into ano2erall score

susp8l9p92:

&2erall score


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Fix Action -ynt esis

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AutoFix tries to )uild fixing actions 8snippets ofinstructions: t at modify t e 2alue of p at l so t att e execution can opefully continue wit outtriggering t e fault &

Find an action snip t at satisfies t e specification re#uire p ; 2 do snip ensure p G 2 end• Auto fix uses " strategies for generating fixing

actions

-etting 7 5odifying t e 2alue of 2aria)les oro) ects t roug assignments or routine calls eplacement7 5odifying t e 2alue of expression

directly w ere t ey are used in t e program


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-.

try to modify t e program state )y calling routines on t e current or ot er o) ects &

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Be a2ioral 5odels


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Candidate Fix eneration

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For a gi2en snap s ot 8l9p92:9 In ecting any fixactions at location < gi2es a modified program t atis a candidate fixWe in ect fix actions in two p ases

Fix sc ema7A template t at a)stracts commoninstruction patterns -c ema Instantiation7 we instantiate t e fixsc ema wit t e snaps ot=s predicate p and somefixing action it induces


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Fix 2alidation

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Fix anking

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% e AutoFix algorit m often finds se2eral 2alidfixes for a gi2en fault.

It is programmer=s responsi)ility to select w icone to deploy

AutoFix ranks t e 2alid fixes according to t e1suspiciousness3 score susp8l9p92: of t e snaps ot8l9p92: t at determined eac fix &


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Experimental E2aluation

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It addresses t e following #uestions


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Experimental setup

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Experimental su) ects 7 % e experiments targeted J code )ases

Base7 Is a data structure.

%xt4i) 7 Is a li)rary to manipulate textdocumentsCards7Is an on*line card gaming systemE*4earn7 Is an application supporting e*learning.


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Kc7no of classes9Kk4&C7t ousands of lines codes9K 7no ofroutines99KL7)oolean #ueries9Kpre7no of cotract clause in preconditions9Kpost7post conditions and class in2ariants8Kin2:

#7


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Experimental results

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Auto Fix produced2alid fixes forMN8J"O: of " Jfaults


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&t er results..

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Auto /x 0rodu!ed 1a.id /xes in'


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conclusion

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Auto fix is an important contri)ution towards t eideal of automatic de)uggingAutoFix generated fixes for J" percent of t efaults.running on standard ardware9 it re#uired ana2erage time per fix under " minutesContracts plays an immediate role.Wit AutoFix9 t e programmer=s de)ugging effortcould )e reduced to almost ero in many cases

automated fixing of programs with contracts.pptx

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