Google的C++编码规范.docx

Google的C++编码规范.docx

《Google的C++编码规范.docx》由会员分享，可在线阅读，更多相关《Google的C++编码规范.docx（13页珍藏版）》请在冰豆网上搜索。

Google的C++编码规范

GoogleC++StyleGuide

Revision3.180

BenjyWeinberger

CraigSilverstein

GregoryEitzmann

MarkMentovai

TashanaLandray

Eachstylepointhasasummaryforwhichadditionalinformationisavailablebytogglingtheaccompanyingarrowbuttonthatlooksthisway:

▶.Youmaytoggleallsummarieswiththebigarrowbutton:

▶ Toggleallsummaries

TableofContents

HeaderFiles

The#defineGuard HeaderFileDependencies InlineFunctions The-inl.hFilesFunctionParameterOrdering NamesandOrderofIncludes

Scoping

Namespaces NestedClasses Nonmember,StaticMember,andGlobalFunctions LocalVariablesStaticandGlobalVariables

Classes

DoingWorkinConstructors DefaultConstructors ExplicitConstructors CopyConstructorsStructsvs.Classes Inheritance MultipleInheritance Interfaces OperatorOverloadingAccessControl DeclarationOrder WriteShortFunctions

Google-SpecificMagic

SmartPointers cpplint

OtherC++Features

ReferenceArguments FunctionOverloading DefaultArguments Variable-LengthArraysandalloca（）Friends Exceptions Run-TimeTypeInformation（RTTI） Casting StreamsPreincrementandPredecrement Useofconst IntegerTypes 64-bitPortability PreprocessorMacros0andNULL sizeof Boost C++0x

Naming

GeneralNamingRules FileNames TypeNames VariableNames ConstantNames FunctionNamesNamespaceNames EnumeratorNames MacroNames ExceptionstoNamingRules

Comments

CommentStyle FileComments ClassComments FunctionComments VariableCommentsImplementationComments Punctuation,SpellingandGrammar TODOComments DeprecationComments

Formatting

LineLength Non-ASCIICharacters Spacesvs.Tabs FunctionDeclarationsandDefinitionsFunctionCalls Conditionals LoopsandSwitchStatements PointerandReferenceExpressionsBooleanExpressions ReturnValues VariableandArrayInitialization PreprocessorDirectivesClassFormat ConstructorInitializerLists NamespaceFormatting HorizontalWhitespaceVerticalWhitespace

ExceptionstotheRules

ExistingNon-conformantCode WindowsCode

ImportantNote

DisplayingHiddenDetailsinthisGuide

▶

Thisstyleguidecontainsmanydetailsthatareinitiallyhiddenfromview.Theyaremarkedbythetriangleicon,whichyouseehereonyourleft.Clickitnow.Youshouldsee"Hooray"appearbelow.

Background

C++isthemaindevelopmentlanguageusedbymanyofGoogle'sopen-sourceprojects.AseveryC++programmerknows,thelanguagehasmanypowerfulfeatures,butthispowerbringswithitcomplexity,whichinturncanmakecodemorebug-proneandhardertoreadandmaintain.

Thegoalofthisguideistomanagethiscomplexitybydescribingindetailthedosanddon'tsofwritingC++code.TheserulesexisttokeepthecodebasemanageablewhilestillallowingcoderstouseC++languagefeaturesproductively.

Style,alsoknownasreadability,iswhatwecalltheconventionsthatgovernourC++code.ThetermStyleisabitofamisnomer,sincetheseconventionscoverfarmorethanjustsourcefileformatting.

Onewayinwhichwekeepthecodebasemanageableisbyenforcing consistency.Itisveryimportantthatanyprogrammerbeabletolookatanother'scodeandquicklyunderstandit.Maintainingauniformstyleandfollowingconventionsmeansthatwecanmoreeasilyuse"pattern-matching"toinferwhatvarioussymbolsareandwhatinvariantsaretrueaboutthem.Creatingcommon,requiredidiomsandpatternsmakescodemucheasiertounderstand.Insomecasestheremightbegoodargumentsforchangingcertainstylerules,butwenonethelesskeepthingsastheyareinordertopreserveconsistency.

AnotherissuethisguideaddressesisthatofC++featurebloat.C++isahugelanguagewithmanyadvancedfeatures.Insomecasesweconstrain,orevenban,useofcertainfeatures.Wedothistokeepcodesimpleandtoavoidthevariouscommonerrorsandproblemsthatthesefeaturescancause.Thisguideliststhesefeaturesandexplainswhytheiruseisrestricted.

Open-sourceprojectsdevelopedbyGoogleconformtotherequirementsinthisguide.

NotethatthisguideisnotaC++tutorial:

weassumethatthereaderisfamiliarwiththelanguage.

HeaderFiles

Ingeneral,every .cc fileshouldhaveanassociated .h file.Therearesomecommonexceptions,suchasunittestsandsmall.cc filescontainingjusta main（） function.

Correctuseofheaderfilescanmakeahugedifferencetothereadability,sizeandperformanceofyourcode.

Thefollowingruleswillguideyouthroughthevariouspitfallsofusingheaderfiles.

The#defineGuard

▶

Allheaderfilesshouldhave #define guardstopreventmultipleinclusion.Theformatofthesymbolnameshouldbe___H_.

HeaderFileDependencies

▶

Don'tusean #include whenaforwarddeclarationwouldsuffice.

InlineFunctions

▶

Definefunctionsinlineonlywhentheyaresmall,say,10linesorless.

The-inl.hFiles

▶

Youmayusefilenameswitha -inl.h suffixtodefinecomplexinlinefunctionswhenneeded.

FunctionParameterOrdering

▶

Whendefiningafunction,parameterorderis:

inputs,thenoutputs.

NamesandOrderofIncludes

▶

Usestandardorderforreadabilityandtoavoidhiddendependencies:

Clibrary,C++library,otherlibraries' .h,yourproject's .h.

Scoping

Namespaces

▶

Unnamednamespacesin .cc filesareencouraged.Withnamednamespaces,choosethenamebasedontheproject,andpossiblyitspath.Donotusea using-directive.

NestedClasses

▶

Althoughyoumayusepublicnestedclasseswhentheyarepartofaninterface,considera namespace tokeepdeclarationsoutoftheglobalscope.

Nonmember,StaticMember,andGlobalFunctions

▶

Prefernonmemberfunctionswithinanamespaceorstaticmemberfunctionstoglobalfunctions;usecompletelyglobalfunctionsrarely.

LocalVariables

▶

Placeafunction'svariablesinthenarrowestscopepossible,andinitializevariablesinthedeclaration.

StaticandGlobalVariables

▶

Staticorglobalvariablesofclasstypeareforbidden:

theycausehard-to-findbugsduetoindeterminateorderofconstructionanddestruction.

Classes

ClassesarethefundamentalunitofcodeinC++.Naturally,weusethemextensively.Thissectionliststhemaindosanddon'tsyoushouldfollowwhenwritingaclass.

DoingWorkinConstructors

▶

Ingeneral,constructorsshouldmerelysetmembervariablestotheirinitialvalues.Anycomplexinitializationshouldgoinanexplicit Init（） method.

DefaultConstructors

▶

Youmustdefineadefaultconstructorifyourclassdefinesmembervariablesandhasnootherconstructors.Otherwisethecompilerwilldoitforyou,badly.

ExplicitConstructors

▶

UsetheC++keyword explicit forconstructorswithoneargument.

CopyConstructors

▶

Provideacopyconstructorandassignmentoperatoronlywhennecessary.Otherwise,disablethemwithDISALLOW_COPY_AND_ASSIGN.

Structsvs.Classes

▶

Usea struct onlyforpassiveobjectsthatcarrydata;everythingelseisa class.

Inheritance

▶

Compositionisoftenmoreappropriatethaninheritance.Whenusinginheritance,makeit public.

MultipleInheritance

▶

Onlyveryrarelyismultipleimplementationinheritanceactuallyuseful.Weallowmultipleinheritanceonlywhenatmostoneofthebaseclasseshasanimplementation;allotherbaseclassesmustbe pureinterface classestaggedwiththeInterface suffix.

Interfaces

▶

Classesthatsatisfycertainconditionsareallowed,butnotrequired,toendwithan Interface suffix.

OperatorOverloading

▶

Donotoverloadoperatorsexceptinrare,specialcircumstances.

AccessControl

▶

Makedatamembers private,andprovideaccesstothemthroughaccessorfunctionsasneeded（fortechnicalreasons,weallowdatamembersofatestfixtureclasstobe protected whenusing GoogleTest）.Typicallyavariablewouldbecalledfoo_ andtheaccessorfunction foo（）.Youmayalsowantamutatorfunction set_foo（）.Exception:

 staticconst datamembers（typicallycalled kFoo）neednotbe private.

DeclarationOrder

▶

Usethespecifiedorderofdeclarationswithinaclass:

 public:

 before private:

methodsbeforedatamembers（variables）,etc.

WriteShortFunctions

▶

Prefersmallandfocusedfunctions.

Google-SpecificMagic

TherearevarioustricksandutilitiesthatweusetomakeC++codemorerobust,andvariouswaysweuseC++thatmaydifferfromwhatyouseeelsewhere.

SmartPointers

▶

Ifyouactuallyneedpointersemantics, scoped_ptr isgreat.Youshouldonlyuse std:

:

tr1:

:

shared_ptr underveryspecificconditions,suchaswhenobjectsneedtobeheldbySTLcontainers.Youshouldneveruse auto_ptr.

cpplint

▶

Use cpplint.py todetectstyleerrors.

OtherC++Features

ReferenceArguments

▶

Allparameterspassedbyreferencemustbelabeled const.

FunctionOverloading

▶

Useoverloadedfunctions（includingconstructors）onlyifareaderlookingatacallsitecangetagoodideaofwhatishappeningwithouthavingtofirstfigureoutexactlywhichoverloadisbeingcalled.

DefaultArguments

▶

Wedonotallowdefaultfunctionparameters,exceptinafewuncommonsituationsexplainedbelow.

Variable-LengthArraysandalloca（）

▶

Wedonotallowvariable-lengtharraysor alloca（）.

Friends

▶

Weallowuseof friend classesandfunctions,withinreason.

Exceptions

▶

WedonotuseC++exceptions.

Run-TimeTypeInformation（RTTI）

▶

WedonotuseRunTimeTypeInformation（RTTI）.

Casting

▶

UseC++castslike static_cast<>（）.Donotuseothercastformatslike inty=（int）x; or inty=int（x）;.

Streams

▶

Usestreamsonlyforlogging.

PreincrementandPredecrement

▶

Useprefixform（++i）oftheincrementanddecrementoperatorswithiteratorsandothertemplateobjects.

Useofconst

▶

Westronglyrecommendthatyouuse const wheneveritmakessensetodoso.

IntegerTypes

▶

Ofthebuilt-inC++integertypes,theonlyoneuse