Addison wesley effective c++ third edition 55 specific ways to improve your programs and designs

EffectiveC++ThirdEdition55Specific
WaystoImproveYourProgramsand
Designs
ByScottMeyers
...............................................
Publisher:AddisonWesleyProfessional
PubDate:May12,2005
PrintISBN:0-321-33487-6
Pages:320

TableofContents|Index

ThefirsttwoeditionsofEffectiveC++wereembracedbyhundredsofthousandsof
programmersworldwide.Thereasonisclear:ScottMeyers'practicalapproachtoC++
describestherulesofthumbusedbytheexpertsthethingstheyalmostalwaysdooralmost
alwaysavoiddoingtoproduceclear,correct,efficientcode.Thebookisorganizedaround55
specificguidelines,eachofwhichdescribesawaytowritebetterC++.Eachisbackedby
concreteexamples.Forthisthirdedition,morethanhalfthecontentisnew,includingadded
chaptersonmanagingresourcesandusingtemplates.Topicsfromthesecondeditionhave
beenextensivelyrevisedtoreflectmoderndesignconsiderations,includingexceptions,design
patterns,andmultithreading.ImportantfeaturesofEffectiveC++include:Expertguidanceon
thedesignofeffectiveclasses,functions,templates,andinheritancehierarchies.Applications
ofnew"TR1"standardlibraryfunctionality,alongwithcomparisonstoexistingstandard
librarycomponents.InsightsintodifferencesbetweenC++andotherlanguages(e.g.,Java,
C#,C)thathelpdevelopersfromthoselanguagesassimilate"theC++way"ofdoingthings.


EffectiveC++ThirdEdition55Specific
WaystoImproveYourProgramsand
Designs
ByScottMeyers

...............................................
Publisher:AddisonWesleyProfessional
PubDate:May12,2005
PrintISBN:0-321-33487-6
Pages:320

TableofContents|Index



Copyright



PraiseforEffectiveC++,ThirdEdition



Addison-WesleyProfessionalComputingSeries



Preface



Acknowledgments

Introduction




Terminology
Chapter1.AccustomingYourselftoC++



Item1:ViewC++asafederationoflanguages



Item2:Preferconsts,enums,andinlinesto#defines



Item3:Useconstwheneverpossible



Item4:Makesurethatobjectsareinitializedbeforethey'reused



Chapter2.Constructors,Destructors,andAssignmentOperators

Item5:KnowwhatfunctionsC++silentlywritesandcalls



Item6:Explicitlydisallowtheuseofcompiler-generatedfunctionsyoudonotwant



Item7:Declaredestructorsvirtualinpolymorphicbaseclasses



Item8:Preventexceptionsfromleavingdestructors



Item9:Nevercallvirtualfunctionsduringconstructionordestruction



Item10:Haveassignmentoperatorsreturnareferenceto*this



Item11:Handleassignmenttoselfinoperator=



Item12:Copyallpartsofanobject

Chapter3.ResourceManagement



Item13:Useobjectstomanageresources.



Item14:Thinkcarefullyaboutcopyingbehaviorinresource-managingclasses.



Item15:Provideaccesstorawresourcesinresource-managingclasses.



Item16:Usethesameformincorrespondingusesofnewanddelete.



Item17:Storenewedobjectsinsmartpointersinstandalonestatements.




Chapter4.DesignsandDeclarations

Item18:Makeinterfaceseasytousecorrectlyandhardtouseincorrectly



Item19:Treatclassdesignastypedesign



Item20:Preferpass-by-reference-to-consttopass-by-value



Item21:Don'ttrytoreturnareferencewhenyoumustreturnanobject



Item22:Declaredatamembersprivate



Item23:Prefernon-membernon-friendfunctionstomemberfunctions

Item24:Declarenon-memberfunctionswhentypeconversionsshouldapplytoall
parameters
Item25:Considersupportforanon-throwingswap
Chapter5.Implementations



Item26:Postponevariabledefinitionsaslongaspossible.



Item27:Minimizecasting.



Item28:Avoidreturning"handles"toobjectinternals.



Item29:Striveforexception-safecode.



Item30:Understandtheinsandoutsofinlining.



Item31:Minimizecompilationdependenciesbetweenfiles.

Chapter6.InheritanceandObject-OrientedDesign



Item32:Makesurepublicinheritancemodels"is-a."



Item33:Avoidhidinginheritednames





Item34:Differentiatebetweeninheritanceofinterfaceandinheritanceof
implementation



Item35:Consideralternativestovirtualfunctions



Item36:Neverredefineaninheritednon-virtualfunction



Item37:Neverredefineafunction'sinheriteddefaultparametervalue

Item38:Model"has-a"or"is-implemented-in-terms-of"throughcomposition



Item39:Useprivateinheritancejudiciously




Item40:Usemultipleinheritancejudiciously
Chapter7.TemplatesandGenericProgramming



Item41:Understandimplicitinterfacesandcompile-timepolymorphism



Item42:Understandthetwomeaningsoftypename



Item43:Knowhowtoaccessnamesintemplatizedbaseclasses



Item44:Factorparameter-independentcodeoutoftemplates

Item45:Usememberfunctiontemplatestoaccept"allcompatibletypes."





Item46:Definenon-memberfunctionsinsidetemplateswhentypeconversionsare
desired



Item47:Usetraitsclassesforinformationabouttypes



Item48:Beawareoftemplatemetaprogramming



Chapter8.Customizingnewanddelete



Item49:Understandthebehaviorofthenew-handler



Item50:Understandwhenitmakessensetoreplacenewanddelete

Item51:Adheretoconventionwhenwritingnewanddelete



Item52:Writeplacementdeleteifyouwriteplacementnew




Chapter9.Miscellany
Item53:Payattentiontocompilerwarnings.





Item54:Familiarizeyourselfwiththestandardlibrary,includingTR1
Item.55:FamiliarizeyourselfwithBoost.



AppendixA.BeyondEffectiveC++



AppendixB.ItemMappingsBetweenSecondandThirdEditions

Index


Copyright
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Dedication
ForNancy,withoutwhomnothingwouldbemuchworthdoing

Wisdomandbeautyformaveryrarecombination.
PetroniusArbiterSatyricon,XCIV

Dedication
AndinmemoryofPersephone,19952004


PraiseforEffectiveC++,ThirdEdition
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Technologies

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TimothyKnox,SoftwareDeveloper
"ThisisafantasticupdateofaclassicC++text.Meyerscoversalotofnew
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copyofthisnewedition."
JeffreySomers,GameProgrammer


"EffectiveC++,ThirdEdition,coversthethingsyoushouldbedoingwhen
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"Thisbookisamust-haveforbothC++veteransandnewbies.Afteryou
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"ReadingthisbooktransformsordinaryC++programmersintoexpertC++
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enoughtostumbleintothetrapslatentinthisrichlanguage.Inthisthird
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stylesthathaveevolvedtousethem.Scott'sengagingwritingstylemakes
iteasytoassimilatehisguidelinesonyourwaytobecominganeffective
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DavidSmallberg,Instructor,DevelopMentor;Lecturer,ComputerScience,
UCLA
"EffectiveC++hasbeencompletelyupdatedfortwenty-first-centuryC++
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practitioners."
MatthewWilson,Ph.D.,authorofImperfectC++


Addison-WesleyProfessionalComputing
Series
BrianW.Kernighan,ConsultingEditor
MatthewH.Austern,GenericProgrammingandtheSTL:UsingandExtending
theC++StandardTemplateLibrary
DavidR.Butenhof,ProgrammingwithPOSIX®Threads
BrentCallaghan,NFSIllustrated
TomCargill,C++ProgrammingStyle
WilliamR.Cheswick/StevenM.Bellovin/AvielD.Rubin,FirewallsandInternet
Security,SecondEdition:RepellingtheWilyHacker

DavidA.Curry,UNIX®SystemSecurity:AGuideforUsersandSystem
Administrators
StephenC.Dewhurst,C++Gotchas:AvoidingCommonProblemsinCoding
andDesign
DanFarmer/WietseVenema,ForensicDiscovery
ErichGamma/RichardHelm/RalphJohnson/JohnVlissides,DesignPatterns:
ElementsofReusableObject-OrientedSoftware
ErichGamma/RichardHelm/RalphJohnsn/JohnVlissides,DesignPatternsCD:
ElementsofReusableObject-OrientedSoftware
PeterHaggar,PracticalJava™ProgrammingLanguageGuide
DavidR.Hanson,CInterfacesandImplementations:TechniquesforCreating
ReusableSoftware


MarkHarrison/MichaelMcLennan,EffectiveTcl/TkProgramming:Writing
BetterProgramswithTclandTk
MichiHenning/SteveVinoski,AdvancedCORBA®ProgrammingwithC++
BrianW.Kernighan/RobPike,ThePracticeofProgramming
S.Keshav,AnEngineeringApproachtoComputerNetworking:ATMNetworks,
theInternet,andtheTelephoneNetwork
JohnLakos,Large-ScaleC++SoftwareDesign
ScottMeyers,EffectiveC++CD:85SpecificWaystoImproveYourPrograms
andDesigns
ScottMeyers,EffectiveC++,ThirdEdition:55SpecificWaystoImproveYour
ProgramsandDesigns
ScottMeyers,MoreEffectiveC++:35NewWaystoImproveYourPrograms
andDesigns
ScottMeyers,EffectiveSTL:50SpecificWaystoImproveYourUseofthe
StandardTemplateLibrary
RobertB.Murray,C++StrategiesandTactics

DavidR.Musser/GillmerJ.Derge/AtulSaini,STLTutorialandReference
Guide,SecondEdition:C++ProgrammingwiththeStandardTemplateLibrary
JohnK.Ousterhout,TclandtheTkToolkit
CraigPartridge,GigabitNetworking
RadiaPerlman,Interconnections,SecondEdition:Bridges,Routers,Switches,
andInternetworkingProtocols
StephenA.Rago,UNIX®SystemVNetworkProgramming
EricS.Raymond,TheArtofUNIXProgramming


MarcJ.Rochkind,AdvancedUNIXProgramming,SecondEdition
CurtSchimmel,UNIX®SystemsforModernArchitectures:Symmetric
MultiprocessingandCachingforKernelProgrammers
W.RichardStevens,TCP/IPIllustrated,Volume1:TheProtocols
W.RichardStevens,TCP/IPIllustrated,Volume3:TCPforTransactions,HTTP,
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W.RichardStevens/BillFenner/AndrewM.Rudoff,UNIXNetwork
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W.RichardStevens/GaryR.Wright,TCP/IPIllustratedVolumes1-3BoxedSet
JohnViega/GaryMcGraw,BuildingSecureSoftware:HowtoAvoidSecurity
ProblemstheRightWay
GaryR.Wright/W.RichardStevens,TCP/IPIllustrated,Volume2:The
Implementation
RuixiYuan/W.TimothyStrayer,VirtualPrivateNetworks:Technologiesand
Solutions
Visitwww.awprofessional.com/series/professionalcomputingformore
informationaboutthesetitles.

Preface
IwrotetheoriginaleditionofEffectiveC++in1991.Whenthetimecamefora
secondeditionin1997,Iupdatedthematerialinimportantways,but,becauseI
didn'twanttoconfusereadersfamiliarwiththefirstedition,Ididmybestto
retaintheexistingstructure:48oftheoriginal50Itemtitlesremainedessentially
unchanged.Ifthebookwereahouse,thesecondeditionwastheequivalentof
fresheningthingsupbyreplacingcarpets,paint,andlightfixtures.
Forthethirdedition,Itoretheplacedowntothestuds.(ThereweretimesI
wishedI'dgoneallthewaytothefoundation.)TheworldofC++hasundergone
enormouschangesince1991,andthegoalofthisbooktoidentifythemost
importantC++programmingguidelinesinasmall,readablepackagewasno
longerservedbytheItemsI'destablishednearly15yearsearlier.In1991,itwas
reasonabletoassumethatC++programmerscamefromaCbackground.Now,
programmersmovingtoC++arejustaslikelytocomefromJavaorC#.In1991,
inheritanceandobject-orientedprogrammingwerenewtomostprogrammers.
Nowthey'rewell-establishedconcepts,andexceptions,templates,andgeneric
programmingaretheareaswherepeopleneedmoreguidance.In1991,nobody
hadheardofdesignpatterns.Nowit'shardtodiscusssoftwaresystemswithout
referringtothem.In1991,workhadjustbegunonaformalstandardforC++.
Nowthatstandardiseightyearsold,andworkhasbegunonthenextversion.
Toaddressthesechanges,IwipedtheslateascleanasIcouldandaskedmyself,
"WhatarethemostimportantpiecesofadviceforpracticingC++programmers
in2005?"TheresultisthesetofItemsinthisnewedition.Thebookhasnew
chaptersonresourcemanagementandonprogrammingwithtemplates.Infact,
templateconcernsarewoventhroughoutthetext,becausetheyaffectalmost
everythinginC++.Thebookalsoincludesnewmaterialonprogramminginthe
presenceofexceptions,onapplyingdesignpatterns,andonusingthenewTR1
libraryfacilities.(TR1isdescribedinItem54.)Itacknowledgesthattechniques
andapproachesthatworkwellinsingle-threadedsystemsmaynotbe

appropriateinmultithreadedsystems.Welloverhalfthematerialinthebookis
new.However,mostofthefundamentalinformationinthesecondedition
continuestobeimportant,soIfoundawaytoretainitinoneformoranother.


(You'llfindamappingbetweenthesecondandthirdeditionItemsinAppendix
B.)
I'veworkedhardtomakethisbookasgoodasIcan,butIhavenoillusionsthat
it'sperfect.IfyoufeelthatsomeoftheItemsinthisbookareinappropriateas
generaladvice;thatthereisabetterwaytoaccomplishataskexaminedinthe
book;orthatoneormoreofthetechnicaldiscussionsisunclear,incomplete,or
misleading,pleasetellme.Ifyoufindanerrorofanykindtechnical,
grammatical,typographical,whateverpleasetellmethat,too.I'llgladlyaddto
theacknowledgmentsinlaterprintingsthenameofthefirstpersontobringeach
problemtomyattention.
EvenwiththenumberofItemsexpandedto55,thesetofguidelinesinthisbook
isfarfromexhaustive.Butcomingupwithgoodrulesonesthatapplytoalmost
allapplicationsalmostallthetimeisharderthanitmightseem.Ifyouhave
suggestionsforadditionalguidelines,Iwouldbedelightedtohearaboutthem.
Imaintainalistofchangestothisbooksinceitsfirstprinting,includingbug
fixes,clarifications,andtechnicalupdates.ThelistisavailableattheEffective
C++Erratawebpage,If
you'dliketobenotifiedwhenIupdatethelist,Iencourageyoutojoinmy
mailinglist.Iuseittomakeannouncementslikelytointerestpeoplewhofollow
myprofessionalwork.Fordetails,consult />SCOTTDOUGLASMEYERSSTAFFORD,OREGON
APRIL2005


Acknowledgments
EffectiveC++hasexistedforfifteenyears,andIstartedlearningC++aboutfive

yearsbeforeIwrotethebook.The"EffectiveC++project"hasthusbeenunder
developmentfortwodecades.Duringthattime,Ihavebenefitedfromthe
insights,suggestions,corrections,and,occasionally,dumbfoundedstaresof
hundreds(thousands?)ofpeople.EachhashelpedimproveEffectiveC++.Iam
gratefultothemall.
I'vegivenuptryingtokeeptrackofwhereIlearnedwhat,butonegeneralsource
ofinformationhashelpedmeaslongasIcanremember:theUsenetC++
newsgroups,especiallycomp.lang.c++.moderatedand
comp.std.c++.ManyoftheItemsinthisbookperhapsmosthavebenefited
fromthevettingoftechnicalideasatwhichtheparticipantsinthesenewsgroups
excel.
Regardingnewmaterialinthethirdedition,SteveDewhurstworkedwithmeto
comeupwithaninitialsetofcandidateItems.InItem11,theideaof
implementingoperator=viacopy-and-swapcamefromHerbSutter's
writingsonthetopic,e.g.,Item13ofhisExceptionalC++(Addison-Wesley,
2000).RAII(seeItem13)isfromBjarneStroustrup'sTheC++Programming
Language(Addison-Wesley,2000).TheideabehindItem17camefromthe
"BestPractices"sectionoftheBoostshared_ptrwebpage,
andwasrefinedby
Item21ofHerbSutter'sMoreExceptionalC++(Addison-Wesley,2002).Item
29wasstronglyinfluencedbyHerbSutter'sextensivewritingsonthetopic,e.g.,
Items8-19ofExceptionalC++,Items1723ofMoreExceptionalC++,and
Items1113ofExceptionalC++Style(Addison-Wesley,2005);DavidAbrahams
helpedmebetterunderstandthethreeexceptionsafetyguarantees.TheNVI
idiominItem35isfromHerbSutter'scolumn,"Virtuality,"intheSeptember
2001C/C++UsersJournal.InthatsameItem,theTemplateMethodand
StrategydesignpatternsarefromDesignPatterns(Addison-Wesley,1995)by
ErichGamma,RichardHelm,RalphJohnson,andJohnVlissides.Theideaof
usingtheNVIidiominItem37camefromHendrikSchober.DavidSmallberg
contributedthemotivationforwritingacustomsetimplementationinItem38.

Item39'sobservationthattheEBOgenerallyisn'tavailableundermultiple
inheritanceisfromDavidVandevoorde'sandNicolaiM.Josuttis'C++
Templates(Addison-Wesley,2003).InItem42,myinitialunderstandingabout
typenamecamefromGregComeau'sC++andCFAQ
(andLeorZolman
helpedmerealizethatmyunderstandingwasincorrect.(Myfault,notGreg's.)
TheessenceofItem46isfromDanSaks'talk,"MakingNewFriends."Theidea
attheendofItem52thatifyoudeclareoneversionofoperatornew,you
shoulddeclarethemall,isfromItem22ofHerbSutter'sExceptionalC++Style.
MyunderstandingoftheBoostreviewprocess(summarizedinItem55)was
refinedbyDavidAbrahams.
EverythingabovecorrespondstowhoorwhereIlearnedaboutsomething,not
necessarilytowhoorwherethethingwasinventedorfirstpublished.
MynotestellmethatIalsousedinformationfromSteveClamage,Antoine
Trux,TimothyKnox,andMikeKaelbling,though,regrettably,thenotesfailto
tellmehoworwhere.
DraftsofthefirsteditionwerereviewedbyTomCargill,GlennCarroll,Tony
Davis,BrianKernighan,JakKirman,DougLea,MoisesLejter,EugeneSantos,
Jr.,JohnShewchuk,JohnStasko,BjarneStroustrup,BarbaraTilly,andNancyL.
Urbano.IreceivedsuggestionsforimprovementsthatIwasabletoincorporate
inlaterprintingsfromNancyL.Urbano,ChrisTreichel,DavidCorbin,Paul
Gibson,SteveVinoski,TomCargill,NeilRhodes,DavidBern,RussWilliams,
RobertBrazile,DougMorgan,UweSteinmüller,MarkSomer,DougMoore,
DavidSmallberg,SethMeltzer,OlegShteynbuk,DavidPapurt,TonyHansen,
PeterMcCluskey,StefanKuhlins,DavidBraunegg,PaulChisholm,AdamZell,
ClovisTondo,MikeKaelbling,NatrajKini,LarsNyman,GregLutz,Tim
Johnson,JohnLakos,RogerScott,ScottFrohman,AlanRooks,RobertPoor,
EricNagler,AntoineTrux,CadeRoux,ChandrikaGokul,RandyMangoba,and

GlennTeitelbaum.
DraftsofthesecondeditionwerereviewedbyDerekBosch,TimJohnson,Brian
Kernighan,JunichiKimura,ScottLewandowski,LauraMichaels,David
Smallberg,ClovisTondo,ChrisVanWyk,andOlegZabluda.Laterprintings
benefitedfromcommentsfromDanielSteinberg,ArunprasadMarathe,Doug
Stapp,RobertHall,CherylFerguson,GaryBartlett,MichaelTamm,Kendall


Beaman,EricNagler,MaxHailperin,JoeGottman,RichardWeeks,Valentin
Bonnard,JunHe,TimKing,DonMaier,TedHill,MarkHarrison,Michael
Rubenstein,MarkRodgers,DavidGoh,BrentonCooper,AndyThomas-Cramer,
AntoineTrux,JohnWait,BrianSharon,LiamFitzpatrick,BerndMohr,Gary
Yee,JohnO'Hanley,BradyPatterson,ChristopherPeterson,FeliksKluzniak,Isi
Dunietz,ChristopherCreutzi,IanCooper,CarlHarris,MarkStickel,ClayBudin,
PanayotisMatsinopoulos,DavidSmallberg,HerbSutter,PajoMisljencevic,
GiulioAgostini,FredrikBlomqvist,JimmySnyder,ByrialJensen,Witold
Kuzminski,KazunobuKuriyama,MichaelChristensen,JorgeYáñezTeruel,
MarkDavis,MartyRabinowitz,AresLagae,andAlexanderMedvedev.
AnearlypartialdraftofthiseditionwasreviewedbyBrianKernighan,Angelika
Langer,JesseLaeuchli,RogerE.Pedersen,ChrisVanWyk,NicholasStroustrup,
andHendrikSchober.ReviewersforafulldraftwereLeorZolman,MikeTsao,
EricNagler,GeneGutnik,DavidAbrahams,GerhardKreuzer,Drosos
Kourounis,BrianKernighan,AndrewKirmse,BalogPal,EmilyJagdhar,Eugene
Kalenkovich,MikeRoze,EnricoCarrara,BenjaminBerck,JackReeves,Steve
Schirripa,MartinFallenstedt,TimothyKnox,YunBai,MichaelLanzetta,Philipp
Janert,GuidoBartolucci,MichaelTopic,JeffScherpelz,ChrisNauroth,Nishant
Mittal,JeffSomers,HalMoroff,VincentManis,BrandonChang,GregLi,Jim
Meehan,AlanGeller,SiddharthaSingh,SamLee,SasanDashtinezhad,Alex
Marin,SteveCai,ThomasFruchterman,CoryHicks,DavidSmallberg,
GunavardhanKakulapati,DannyRabbani,JakeCohen,HendrikSchober,Paco

Viciana,GlennKennedy,JeffreyD.Oldham,NicholasStroustrup,Matthew
Wilson,AndreiAlexandrescu,TimJohnson,LeonMatthews,PeterDulimov,
andKevlinHenney.DraftsofsomeindividualItemswerereviewedbyHerb
SutterandAttilaF.Feher.
Reviewinganunpolished(possiblyincomplete)manuscriptisdemandingwork,
anddoingitundertimepressureonlymakesitharder.Icontinuetobegrateful
thatsomanypeoplehavebeenwillingtoundertakeitforme.
Reviewingisharderstillifyouhavenobackgroundinthematerialbeing
discussedandareexpectedtocatcheveryprobleminthemanuscript.
Astonishingly,somepeoplestillchoosetobecopyeditors.Chrysta
Meadowbrookewasthecopyeditorforthisbook,andherverythoroughwork
exposedmanyproblemsthateludedeveryoneelse.


LeorZolmancheckedallthecodeexamplesagainstmultiplecompilersin
preparationforthefullreview,thendiditagainafterIrevisedthemanuscript.If
anyerrorsremain,I'mresponsibleforthem,notLeor.
KarlWiegersandespeciallyTimJohnsonofferedrapid,helpfulfeedbackon
backcovercopy.
JohnWait,myeditorforthefirsttwoeditionsofthisbook,foolishlysignedup
foranothertourofdutyinthatcapacity.Hisassistant,DeniseMickelsen,adroitly
handledmyfrequentpesteringwithapleasantsmile.(AtleastIthinkshe'sbeen
smiling.I'veneveractuallyseenher.)JulieNahildrewtheshortstrawandhence
becamemyproductionmanager.Shehandledtheovernightlossofsixweeksin
theproductionschedulewithremarkableequanimity.JohnFuller(herboss)and
MartyRabinowitz(hisboss)helpedoutwithproductionissues,too.Vanessa
Moore'sofficialjobwastohelpwithFrameMakerissuesandPDFpreparation,
butshealsoaddedtheentriestoAppendixBandformatteditforprintingonthe
insidecover.SolveigHauglandhelpedwithindexformatting.SandraSchroeder
andChutiPrasertsithwereresponsibleforcoverdesign,thoughChutiseemsto

havebeentheonewhohadtoreworkthecovereachtimeIsaid,"Butwhatabout
thisphotowithastripeofthatcolor...?"ChandaLeary-Coutugottappedforthe
heavyliftinginmarketing.
DuringthemonthsIworkedonthemanuscript,theTVseriesBuffytheVampire
Slayeroftenhelpedme"de-stress"attheendoftheday.Onlywithgreatrestraint
haveIkeptBuffyspeakoutofthebook.
KathyReedtaughtmeprogrammingin1971,andI'mgratifiedthatweremain
friendstothisday.DonaldFrenchhiredmeandMoisesLejtertocreateC++
trainingmaterialsin1989(anactthatledtomyreallyknowingC++),andin
1991heengagedmetopresentthematStratusComputer.Thestudentsinthat
classencouragedmetowritewhatultimatelybecamethefirsteditionofthis
book.DonalsointroducedmetoJohnWait,whoagreedtopublishit.
Mywife,NancyL.Urbano,continuestoencouragemywriting,evenafterseven
bookprojects,aCDadaptation,andadissertation.Shehasunbelievable
forbearance.Icouldn'tdowhatIdowithouther.
Fromstarttofinish,ourdog,Persephone,hasbeenacompanionwithoutequal.


Sadly,formuchofthisproject,hercompanionshiphastakentheformofanurn
intheoffice.Wereallymissher.


Introduction
Learningthefundamentalsofaprogramminglanguageisonething;learning
howtodesignandimplementeffectiveprogramsinthatlanguageissomething
elseentirely.ThisisespeciallytrueofC++,alanguageboastinganuncommon
rangeofpowerandexpressiveness.Properlyused,C++canbeajoytowork
with.Anenormousvarietyofdesignscanbedirectlyexpressedandefficiently
implemented.Ajudiciouslychosenandcarefullycraftedsetofclasses,
functions,andtemplatescanmakeapplicationprogrammingeasy,intuitive,

efficient,andnearlyerror-free.Itisn'tundulydifficulttowriteeffectiveC++
programs,ifyouknowhowtodoit.Usedwithoutdiscipline,however,C++can
leadtocodethatisincomprehensible,unmaintainable,inextensible,inefficient,
andjustplainwrong.
ThepurposeofthisbookistoshowyouhowtouseC++effectively.Iassume
youalreadyknowC++asalanguageandthatyouhavesomeexperienceinits
use.WhatIprovidehereisaguidetousingthelanguagesothatyoursoftwareis
comprehensible,maintainable,portable,extensible,efficient,andlikelyto
behaveasyouexpect.
TheadviceIprofferfallsintotwobroadcategories:generaldesignstrategies,
andthenutsandboltsofspecificlanguagefeatures.Thedesigndiscussions
concentrateonhowtochoosebetweendifferentapproachestoaccomplishing
somethinginC++.Howdoyouchoosebetweeninheritanceandtemplates?
Betweenpublicandprivateinheritance?Betweenprivateinheritanceand
composition?Betweenmemberandnon-memberfunctions?Betweenpass-byvalueandpass-by-reference?It'simportanttomakethesedecisionscorrectlyat
theoutset,becauseapoorchoicemaynotbecomeapparentuntilmuchlaterin
thedevelopmentprocess,atwhichpointrectifyingitisoftendifficult,timeconsuming,andexpensive.
Evenwhenyouknowexactlywhatyouwanttodo,gettingthingsjustrightcan
betricky.What'stheproperreturntypeforassignmentoperators?Whenshoulda
destructorbevirtual?Howshouldoperatornewbehavewhenitcan'tfind
enoughmemory?It'scrucialtosweatdetailslikethese,becausefailuretodoso


almostalwaysleadstounexpected,possiblymystifyingprogrambehavior.This
bookwillhelpyouavoidthat.
ThisisnotacomprehensivereferenceforC++.Rather,it'sacollectionof55
specificsuggestions(IcallthemItems)forhowyoucanimproveyourprograms
anddesigns.EachItemstandsmoreorlessonitsown,butmostalsocontain
referencestootherItems.Onewaytoreadthebook,then,istostartwithanItem
ofinterest,thenfollowitsreferencestoseewheretheyleadyou.

Thebookisn'tanintroductiontoC++,either.InChapter2,forexample,I'm
eagertotellyouallabouttheproperimplementationsofconstructors,
destructors,andassignmentoperators,butIassumeyoualreadyknoworcango
elsewheretofindoutwhatthesefunctionsdoandhowtheyaredeclared.A
numberofC++bookscontaininformationsuchasthat.
ThepurposeofthisbookistohighlightthoseaspectsofC++programmingthat
areoftenoverlooked.Otherbooksdescribethedifferentpartsofthelanguage.
Thisbooktellsyouhowtocombinethosepartssoyouendupwitheffective
programs.Otherbookstellyouhowtogetyourprogramstocompile.Thisbook
tellsyouhowtoavoidproblemsthatcompilerswon'ttellyouabout.
Atthesametime,thisbooklimitsitselftostandardC++.Onlyfeaturesinthe
officiallanguagestandardhavebeenusedhere.Portabilityisakeyconcernin
thisbook,soifyou'relookingforplatform-dependenthacksandkludges,thisis
nottheplacetofindthem.
Anotherthingyouwon'tfindinthisbookistheC++Gospel,theOneTruePath
toperfectC++software.EachoftheItemsinthisbookprovidesguidanceon
howtodevelopbetterdesigns,howtoavoidcommonproblems,orhowto
achievegreaterefficiency,butnoneoftheItemsisuniversallyapplicable.
Softwaredesignandimplementationisacomplextask,onecoloredbythe
constraintsofthehardware,theoperatingsystem,andtheapplication,sothebest
Icandoisprovideguidelinesforcreatingbetterprograms.
Ifyoufollowalltheguidelinesallthetime,youareunlikelytofallintothemost
commontrapssurroundingC++,butguidelines,bytheirnature,haveexceptions.
That'swhyeachItemhasanexplanation.Theexplanationsarethemost
importantpartofthebook.OnlybyunderstandingtherationalebehindanItem


canyoudeterminewhetheritappliestothesoftwareyouaredevelopingandto
theuniqueconstraintsunderwhichyoutoil.
ThebestuseofthisbookistogaininsightintohowC++behaves,whyit

behavesthatway,andhowtouseitsbehaviortoyouradvantage.Blind
applicationoftheItemsinthisbookisclearlyinappropriate,butatthesame
time,youprobablyshouldn'tviolateanyoftheguidelineswithoutagoodreason.


Terminology
ThereisasmallC++vocabularythateveryprogrammershouldunderstand.The
followingtermsareimportantenoughthatitisworthmakingsureweagreeon
whattheymean.
Adeclarationtellscompilersaboutthenameandtypeofsomething,butitomits
certaindetails.Thesearedeclarations:

externintx;//objectdeclar

std::size_tnumDigits(intnumber);//functiondecl

classWidget;//classdeclara

template<typenameT>//templatedecl

classGraphNode;//(seeItem42

//theuseof"t

NotethatIrefertotheintegerxasan"object,"eventhoughit'sofbuilt-intype.
Somepeoplereservethename"object"forvariablesofuser-definedtype,but
I'mnotoneofthem.AlsonotethatthefunctionnumDigits'returntypeis
std::size_t,i.e.,thetypesize_tinnamespacestd.Thatnamespaceis
wherevirtuallyeverythinginC++'sstandardlibraryislocated.However,