on the impact of feature dependencies when maintaining preprocessor-based software product lines

OntheImpactofFeatureDependencieswhenMaintaining

Preprocessor‐basedSo<wareProductLines

MárcioRibeiroFelipeQueirozPauloBorba

TársisTolêdoClausBrabrandSérgioSoares

{mmr3,Cq,phmb,twt,scbs}@cin.ufpe.br

brabrand@itu.dk

VirtualSeparaKonofConcerns(VSoC)

2

ButnotenoughforFeatureModularity…

3

Problem

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 Developerscanintroducecompila?onandbehavioralerrorstofeaturesduetofeaturedependencies…

…leadingtolowerproducKvity

 LateerrordetecKon  Developersdiscovertheproblemonlywhencompilingandexecu?ngtheproblema?cproduct

 DifficultnavigaKon  Developersnotawareoffeaturedependencies

  EvenworsewhenusingVSoC:featuresarehidden!

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Tominimizetheseproblems:

EmergentInterfaces

EmergentInterfacesinanutshell

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Dependenciescaptured!Developerscanfocusontheimpactedfeatures…

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Featuredependenciescancauseproblems

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EmergentInterfacescomplementVSoC

Agenda

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Studysecngs

 43Preprocessor‐basedSoMwareProductlines  JavaandC  Differentsizesanddomains

 Scripttoolforcompu?ngtwometrics: MDi:numberofmethodswithpreprocessordirec?ves MDe:numberofmethodswithfeaturedependencies

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Featuredependenciesourtoolconsiders

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EffortesKmaKon:VSoCvs.EmergentInterfaces

14Num

berofFragm

ents

Num

berofFeatures

MethodsselecKon

 Randomlymethodsselec?on  Only methods that contain the feature dependencieswefocusonthiswork

 Whichmethodsshouldweselect? Manyfragments:favoringemergentinterfaces

  Fewfragments:nodifferences

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Groups

 Twogroups:

 Why2asathreshold?  Differencesbetweenbothapproachesappearfrom2

  1:bothapproacheshavealwaysthesameeffortes?ma?on

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MethodsselecKontofitthegroups

 Propor?onalselec?onaccordingtoeachSPL

 Example:libxml2  Group1:953methods(8methodsselected)  Group2:125methods(1methodselected)

 Majority(23productlines)  1:1

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GeneralalgorithmforeffortesKmaKon

 Whilewedonotreach3replica?ons  Foreachproductline

  Randomlyselectmethodspropor?onallyaccording to thegroups

  Foreachmethod  Randomlyselectavariable

  From this variable, computeNoFa,NoFe, and LOC for bothapproaches

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Results

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QuesKon1:howoMenmethodswithpreprocessordirec?vescontainfeature

dependencies?

Frequencyoffeaturedependencies

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MethodswithDependencies

MethodswithDirecKves

Ourdatarevealthat…

 Methods with direc?ves that also contain thefeaturedependencieswestudied: Max:88%(mobile‐rss)

 Min:12%(lampiro)

 So, the featuredependenciesweconsideredmaybecommoninthe43SPLsweanalyzed  Only6SPLshaveMDe/MDi<50%

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QuesKon2:howfeaturedependenciesimpact

maintenanceeffortwhenusingVSoCandemergent

interfaces?

SelecKon:methods,groups,SPLs

 Foreachreplica?on:115methods

 Methodsselec?onaccordingtoeachproductline

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EmergentInterfaceseffortesKmaKon

 Effortes?ma?oninallSPLs

 Methodsdistribu?onbygroups:

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Whenincreasingthenumberoffragments…

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 … the percentage of methods where EmergentInterfacesachieveeffortreduc?onalsoincreases…

65%

70%

75%

80%

85%

90%

95%

100%

>2 >3 >4 >5 >6

Replica?on1

Replica?on2

Replica?on3

EsKmaK

onofEffortred

ucKon

NumberofFragments

Threatstovalidity

 Metricsandeffortes?ma?on  Timebehermeasureseffort…  …butthemetricsares?lluseful

  Overheadtocomputeemergentinterfaces

 Dependencies  Interprocedural,chainofassignments…(notcomputed)

  So,thenumberswepresentedmightbeevenhigher…

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Concludingremarks

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 How oMen the feature dependencies we analyzedoccurinprac?ce? Max:88%;Min:12%;Majority>50%

 Emergentinterfacescanachieveeffortreduc?on  For the majority of the studied methods (65%): sameeffortofVSoC

  Nega?veimpactofVSoCisnotsocommon

 More significant effort reduc?ons: methods withmanyfragments(Group1)