2023年C++常见英文面试笔试题

C/C+＋PｒogramminginｔeｒvieｗｑuestioｎsａndanswerｓBySａtｉｓhShｅｔty，Jｕly14th,２023Ｗhａtiｓenｃaｐsulation?？

Cｏntａｉninｇandhidingiｎｆormａtionａboutａnobject,ｓｕchasｉnterｎaldatａｓtructuｒesａｎｄcode.Encａpｓulaｔioｎisｏlａtes（使隔离)ｔheintｅrnaｌcｏmｐlｅxityofaｎobject'sopｅraｔionfｒｏmthｅrestoftheappｌicaｔｉoｎ.Forexample,aclieｎｔcｏｍpｏnentaｓkｉngfoｒnｅtrevenuｅ(收益）froｍａbuｓineｓsoｂjectnｅednotknowthedata'soｒｉｇｉn.ﻫＷhaｔiｓinheritance?Iｎheritanceａlloｗsoneｃlasstｏｒeusethｅsｔaｔeａndbｅhavｉorofanotherclａsｓ.Thedｅrivedclasｓinheritstheｐroｐｅrtｉesandmethodimplementaｔiｏnｓｏfthebaseclassandextendｓitbyｏvｅrrｉｄingmetｈoｄsａｎdaddingaddｉｔiｏnalprｏpｅrｔiesandmeｔhodｓ.

WhatisＰｏlｙmｏrphism？？Poｌymｏrphｉｓmallowsａｃlieｎｔtｏtｒｅａｔdｉffｅｒｅntoｂjｅctsintｈeｓａｍｅｗaｙeｖenifｔheywｅｒecreatedfromdifferenｔcｌassesanｄｅxhibiｔ(展现)ｄifferｅntbehavｉors.Yｏucaｎusｅiｍplementation（实现)inheritanｃetｏａｃｈieveｐolymorphisｍinlanguaｇesｓuchaｓC+＋andJava.Basecｌａｓｓobｊect'spoinｔeｒｃaｎiｎvoke(调用）metｈodｓｉndeｒｉveｄclaｓsoｂjects．YoｕcａnalsｏａchievepｏlｙｍorｐhｉsmｉnC＋+byfunctｉｏｎoveｒｌoａｄingａｎdoperａtｏroverloadinｇ.ﻫWhａtiscｏnstructｏroｒctｏｒ?Constｒuctｏrｃreａtesａnobjｅctaｎdｉnitializｅsit．Itａlsoｃreatesvtable变量列表?forvirｔualfunｃtiｏnｓ．Ｉtisdiffeｒentｆromotｈeｒmetｈｏdsinａclaｓs.ﻫWｈａｔiｓdestｒucｔｏr?Deｓtｒｕcｔorｕsｕallydeletesａnyｅxｔｒarｅsouｒceｓalloｃａtedｂytｈeｏｂject．ﻫＷhatｉsdｅfaultconｓｔruｃtor?Constｒuｃtorwｉthｎoargｕmenｔｓｏrallｔhｅargumentsｈasdefａultvalues.

Whatiｓcopyconsｔructor?Ｃonsｔructorwhichｉnitiａｌizeｓtheiｔ＇ｓobjeｃtmembervariabｌeｓ(ｂyshaｌlowcopyinｇ)ｗitｈａnｏｔherｏbjｅｃtofthesａmeｃｌasｓ．Iｆyoudon'timpｌementonｅinｙｏurｃｌａssｔhencompilerｉmｐlｅｍｅｎtsoneｆoryｏu．fｏｒexaｍpｌe:

BooＯbj1（１0);／/callingBoｏｃonstructoｒBoｏObj２(Obj1)；//cａlliｎgbooｃｏｐyｃonstｒuｃtor

BoｏObj2＝Ｏｂｊ1;//cａllingbooｃopycｏnsｔｒucｔoｒＷheｎａｒｅcopyconstｒucｔoｒscalleｄ?Copyconstｒuctorsａrecalｌeｄｉnfollｏwingcａsｅs：ﻫａ）ｗhｅnafuncｔionreｔｕｒｎsａｎoｂjｅｃtoｆthatclassbyvalueﻫb)ｗhenｔｈeｏbjectofｔhａtｃlasｓｉｓpａssedbyｖaｌｕeａｓanａｒgumenｔtｏafunｃtion

ｃ)ｗhｅnyouｃonｓtrｕctanobｊectbaｓedonanotherobjecｔofｔheｓamｅcｌass

d)Whencoｍpilergenｅratesateｍpｏrａrｙobjeｃt

Whatiｓａssｉgｎmentoperatoｒ?Defaulｔasｓiｇnmentoperａtorhandｌesａsｓigｎｉnｇoneobjeｃttｏａnotｈｅrofｔｈesａmeclaｓs.Meｍbertomｅmbeｒcopy(shａllowcopｙ)

Whａtareallthｅimplｉcitmemｂｅｒfuｎcｔionsoftheｃｌass？Ｏrwｈatareaｌｌｔｈｅｆuｎｃtionswhichcoｍpiｌerｉmplｅｍｅntsfｏruｓifｗｅdoｎ'tdeｆiｎｅoｎｅ.？?deｆaｕｌtctor

ｃoｐyctorﻫａｓsｉgnmeｎtoｐｅｒaｔorﻫdｅｆauｌｔdesｔrｕctｏrﻫａｄdressoｐｅratｏrﻫWhatｉsｃoｎverｓiｏncｏｎｓtｒuctｏr？cｏnｓｔｒｕctorｗithasinglearｇｕmentmakesｔhaｔcｏnsｔructoraｓｃoｎversｉonctｏrａnｄitｃanbｅuseｄfortｙpecｏnverｓion．fｏreｘampｌe:ｃlａsｓＢoｏﻫ{ﻫpuｂlic:ﻫＢoo(intｉ);ﻫ}；ﻫBooBooOｂject=１0;/／ａssigninｇint１0Ｂoｏobjeｃtﻫ

Whatiｓｃｏnversiｏnopｅrator??

ｃlasscanhavｅａpublicmｅthodｆorsｐecificdatatypｅcｏnveｒｓｉons．ｆoｒeｘamplｅ:

classBoo

{ﻫｄｏublevalue；

publｉｃ:ﻫBoo(inti)

oｐｅrａtoｒｄoublｅ（)

｛ﻫretuｒｎｖaｌue;ﻫ｝

}；

ＢooBooObject;ﻫｄoｕbleｉ=BooＯbject；/／ａsｓｉgnｉｎｇｏbjeｃttovaｒiaｂleioftyｐeｄｏuble.nowcｏnｖｅrsiｏnopｅｒatoｒgetscalledtoassiｇｎthevalue.ﻫ

Whａtisdiffbetweenmaｌloc()/frｅｅ()ａndnew／delete?maｌlｏcallocatesmemｏｒyｆoｒobjectｉｎhｅapbutdoesn'tiｎｖｏkｅｏbｊｅct'sconstrucｔortoinitiａlliｚethｅoｂject.ｎewalloｃatｅsmｅmｏryａnｄaｌsoinvｏkｅｓconsｔrｕctortｏinitialiｚｅｔｈeoｂject.mａlloc（）anｄfreｅ（）ｄonotsupporｔobｊｅctseｍanticsﻫＤoｅsnｏtｃonstructａnddestｒuctobjecｔs

striｎg*pｔr=（sｔｒing*)(malｌoc（sｉzeof(string))）

Ａｒenotsafｅ

Ｄoeｓnotcalcｕlatetｈesiｚeoｆthｅobjｅｃｔsthatｉtｃonstruct

Rｅtuｒｎsapointｅｒtovoidﻫiｎt*p＝(int*)（malloc（ｓｉzeoｆ(ｉnt）));ﻫinｔ*p=neｗiｎｔ;ﻫArｅnｏtexｔensｉｂｌeﻫnewanｄｄｅleteｃanｂeｏverｌoａdｅdinaｃlａsｓ"dｅlete"ｆiｒsｔcaｌlstｈeoｂjeｃt'stermｉnationrｏutine（i.ｅ．ｉtｓdeｓｔｒuctor）anｄｔhｅnrｅleasesthespaｃetheoｂｊectｏccupiｅdｏnthｅheapmｅmory．Iｆanarrayofoｂjeｃｔｓwａsｃreatedｕｓingnｅｗ,thendeletemuｓｔbetoldｔhａtitisｄeａlinｇwithaｎarrａybｙprecedｉngｔhenaｍｅwｉthａnｅmpty[]:－Int_t*ｍy_ｉntｓ=neｗＩnt＿t[１０];..．delｅte[]my_ints;

whaｔistｈediffbｅtweｅn"ｎew"and＂operatoｒnew"?ﻫ＂opeｒａｔｏrｎew＂ｗoｒkｓｌikｅmaｌｌｏｃ．ﻫﻫＷhatisdifｆerencebeｔweｅｎｔｅmpｌaｔeaｎdmacro??Thｅｒeisnｏwaｙｆortheｃompilertoｖerifythaｔｔhemaｃrｏｐarａmetersarｅofｃｏｍpaｔibletyｐeｓ.Ｔhemacｒoiｓexpandedｗitｈoutａｎｙｓpecialtｙpechｅｃkiｎg.Ifmacroparａmｅｔeｒhasapost-inｃrｅmenteｄvariable（ｌikec+＋),theｉｎcｒeｍentｉspｅｒｆorｍedtwoｔimes.Bｅcａusemacrosaｒeexｐandedｂytheｐrepｒocessor,compｉlｅreｒroｒmeｓsaｇｅswｉllｒefｅrtotheｅxpandedｍaｃro,ｒaｔheｒthanthｅmacrodｅｆinitionｉｔｓｅlf.Ａｌso,ｔｈemacｒowillｓhowuｐｉnexｐａｎdedformduｒiｎgdebuggｉng.foreｘａmplｅ:Macｒｏ:#ｄefineｍiｎ(i,j)(i<j?i:j）ｔemｐlaｔe:

tempｌate＜classT>ﻫTmin(Ti,Tｊ）

{ﻫrｅturnｉ＜j?i:j;

}ﻫ

ﻫＷhａtarｅC+＋stｏragecｌasseｓ？auto

regiｓterﻫsｔａticﻫeｘｔｅrｎauto:tｈedeｆault.Variaｂｌｅｓaｒｅaｕtomａｔicaｌlycreaｔedandinitialiｚedwｈentｈｅｙarｅdｅfinｅｄａndarｅdesｔrｏｙedａttheenｄｏftheblｏckcontａinｉｎgｔheirdefinｉtioｎ.Theｙaｒeｎｏtvisibleoｕtsｉdetｈaｔblockreｇisｔｅｒ:ａtypeoｆａｕtｏvariabｌe．ａsuggｅsｔioｎtoｔｈｅcompｉlertｏuｓeaCＰＵrｅgistｅrfｏrperformanｃeｓtaｔic:avariabｌｅthatｉsknｏwnoｎlyｉｎthｅfunctｉonｔhatcontaiｎｓｉｔｓdeｆiｎitionbｕtisnｅvｅｒdeｓtroｙeｄａndrｅtaｉｎs=keepｉｔsvalueｂetweenｃallｓtoｔhaｔfunction.Itexisｔsfｒoｍｔhetimｅtheprogrambegｉｎsexecuｔiｏnｅxtern:aｓtaticvariabｌeｗhoｓｅdefinitiｏnandｐlaｃemenｔisｄetermｉｎedwhenａllobjｅcｔanｄｌibrarymoｄulesarecombｉned（lｉｎｋed)toforｍthｅexｅｃutablｅｃodefile.Itcanbevｉsｉbleoｕtsidetｈefilｅwhｅreitiｓdefiｎed.

ﻫWhatａｒeｓｔorａｇeqｕａlifiｅｒsiｎC+＋?Theyare..coｎstﻫｖolatile

mutaｂleConstkeyｗｏrｄindicatesthaｔmemoryoｎcｅｉniｔｉａｌized,shｏｕldnｏtｂealteｒedbyaprogram．ｖolaｔilekeｙｗorｄiｎdicaｔesthａｔtｈevalueｉnthｅmeｍorylocationcａnbeaｌtｅreｄeventhoughｎothinginｔhｅprogｒamﻫcoｄeｍodｉｆiesｔhｅｃoｎｔｅnts．forexａmｐleifyouhａvｅapoiｎtｅrtｏｈardwａrｅｌｏcationthatcoｎｔainsthetiｍe,ｗｈｅrｅhardwareｃhangesｔhｅvalueofthisｐointervａriａbleaｎｄｎｏttheproｇram.Thｅiｎtentofthiskeyworｄtoimprｏveｔｈeoptimizatｉonabｉlityofｔｈeｃoｍpiler.muｔableｋeｙｗｏrdinｄicatesｔｈatparticuｌarmemberｏfastrｕctureorｃlaｓsｃaｎbeａlｔeredeｖeniｆapａrticularsｔructurevａriabｌｅ,class，oｒcｌassｍｅmbeｒｆunctioｎiscｏnstant．ｓｔruｃtdａｔａﻫ{ﻫcharname[８0];ﻫmuｔａbledoublesalary;

}conｓtdａtaMyＳｔruct=｛"SatisｈＳｈetty"，１000};//ｉnitｌizｅdbycｏmplierｓｔrcpｙ（ＭyStruct．name，＂ShilpａShetｔy");//ｃｏmpileｒerroｒ

MyStruｃt.salaray=2０２3;//complierｉshappyａlｌowｅdﻫﻫＷhatisrefｅreｎce??ｒefｅrｅnｃeisanａmeｔｈａｔacｔｓａｓanaliａs,oｒalteｒnａｔiveｎaｍｅ,ｆｏraprｅviousｌydefineｄｖarｉableoranobjｅct.pｒeｐeｎdiｎｇvariablewiｔh"&"symbolmakｅｓｉtasrｅferenｃe.forｅxａｍpｌe：inta;

iｎt＆b=a;&读ａmp

ﻫWhatispassｉnｇbyrｅfereｎce?Ｍethodofpassｉnｇaｒguｍentｓtoaｆｕｎctionwhiｃhｔakespａrａmeｔeroftypeｒeｆｅrence.forｅxampｌe:ｖoidswａｐ（int＆ｘ,int＆ｙ)ﻫ{ﻫinｔｔemp=x；ﻫx=y;

y=temp；

}inｔａ=2,b＝3；sｗap（a,b）;ﻫBasically,insidｅtｈefunctｉoｎtｈereｗon＇tbeanycopｙofｔheａrgｕmenｔｓ＂x"and"ｙ"insteaｄtheyｒefeｒtooriｇinａｌｖariaｂlｅsaａndb．soｎoeｘtramｅmoryneeｄedｔｏｐassarguｍeｎtｓaｎditｉｓｍoreefficｉeｎt.ﻫ

Ｗhｅndｏuse"coｎｓt"refｅreｎceaｒgumentsinｆuｎctｉon?a）Usingconstpｒoｔｅctsyｏuagaｉnstpｒograｍmiｎgerrｏｒstｈaｔｉnadvertenｔly不经意的alterdatａ.

b)Usingconstａlｌowsｆunctioｎtoproｃessbothcｏnsｔandnon-cｏnsｔactｕａｌａｒｇumentｓ,whiｌｅafunctionwithouｔcoｎstintｈeｐrototypｅｃanoｎlyacceptnonconstantaｒguｍｅntｓ.

c)Usiｎgaｃonｓtrefeｒeｎceallowsthefunctioｎtogenerateandｕｓeａｔeｍpｏraryvaｒiablｅaｐpropriaｔｅly．ﻫﻫﻫＷｈeｎａrｅtｅｍpｏrａryvariａｂlescreateｄbyC++ｃｏｍpｉler?Pｒovidｅdthaｔfｕnｃtｉonpaｒameterisa"coｎｓｔｒefｅｒｅnｃe",cｏｍｐilerｇenｅｒatesｔemporarｙvaｒiａｂlｅｉnｆｏllowing2waｙｓ.ａ)Theａctualａrｇｕmentistheｃorrecttype，buｔｉｔｉsn'tＬvａluｅdｏubleＣubｅ（constdoｕbｌｅ＆ｎum)

{

num=nｕm*ｎum＊num;ﻫreｔｕrnnuｍ;｝doubｌｅtemp=2．0；ﻫdoublevalｕe=cubｅ(3.0+temｐ);//ａｒgｕmeｎｔisaexpresｓｉｏnaｎdnｏtaLvａlue;ﻫｂ)Thｅａctuａｌarｇuｍentiｓofｔhｅｗroｎgｔype，buｔofaｔyｐeｔhatcaｎｂeconｖertedtoｔhecorrｅｃttｙｐelonｇtｅmp=3L;ﻫdouｂlevalue=cuberoot(ｔemp）；／／lｏｎgtｏｄoubleconversｉonﻫﻫﻫＷｈatisviｒtuａlfunction？ﻫWhendｅrｉvｅdclａssｏvｅrridesthebaseclaｓｓmethｏdbyredｅfiｎinｇｔｈesamefuｎｃtｉoｎ,ｔｈenｉfclientwantstoａcceｓsredｅfiｎedthｅmｅｔhｏdfromｄerivedclasｓthroughａｐoiｎtｅrfｒombaｓeｃlａssobject,ｔhenyｏｕmustｄefinｅthisfuｎｃtｉoniｎｂaseclassasvｉrtuaｌｆunｃtion.clasｓparentﻫ{

vｏiｄShｏw（)

{

cout<<"ｉ'mｐarent"＜＜endl；ﻫ}

}；ﻫcｌasｓchｉld:pｕblicｐａrentﻫ｛ﻫvoidＳhow(）ﻫ{

cout＜<"ｉ＇ｍchild＂<＜enｄl;

｝};ﻫparent*parent＿obｊect_ｐtr=ｎewcｈiｌｄ;paｒent_obｊecｔ_ptr->show(）/／callspareｎｔ->sｈoｗ()iﻫｎowwegotoviｒtuａｌworlｄ.．．clasｓpａrent

{ﻫｖｉrｔuaｌｖoｉdShｏw()

｛

cout<<＂i'mparent＂＜＜endｌ;ﻫ}

}；

cｌassｃｈilｄ:ｐuｂliｃparentﻫ{ﻫｖoidShow(）

{

cout<<＂ｉ'mchild"<＜eｎdl;

｝};ﻫparｅnt*parent_objｅct_ｐtr=nｅwchiｌd；pａｒenｔ_object_ptr->sｈow（)//cａllschｉｌd－>ｓhｏｗ(）ﻫﻫ

Whatispureｖirtualfuncｔioｎ?ｏrwhatisabstractｃlasｓ?

Whenyoｕｄefiｎｅonlｙfunctｉonproｔｏtypｅinabasｅclａsｓwithouｔiｍｐlemeｎｔatioｎａnddｏthecomplｅteｉmplｅmｅｎtａtion实现iｎdｅrｉvedclaｓs.Ｔhiｓbａsｅclasｓiscａlｌｅdabｓtractclａｓｓanｄcｌieｎtwｏn'tａbletoinstantｉateanoｂjectｕsiｎgthｉsbaseclaｓs.Ｙoucanmaｋｅａpurevｉrtｕａlfｕnctｉonｏｒａbstractｃｌassthisｗay．.claｓｓBｏｏﻫ{ﻫvoiｄｆoo(）=０;

}ﻫBooMyBｏo;/／compilatｉonerrｏrﻫ

WｈａｔiｓMｅmｏryaｌiｇｎｍent?？Theｔｅrmaｌigｎｍeｎtｐrｉmaｒｉlｙｍeanstｈetendｅncy趋向ofanadｄreｓｓpointervａlｕｅtobeamuｌtipleofsomepowerｏftwo.Soapｏｉｎtｅｒwｉtｈtwｏbｙtｅalignmenthasaｚeroｉnthelｅastｓignｉfｉcanｔｂit.Aｎｄapｏiｎterwitｈfourｂyｔeaｌiｇｎｍeｎtｈasazeroｉｎboｔｈthetwｏleastｓignifｉcａntbits.Anｄｓoon．Ｍｏｒｅalignｍentmeansalongeｒｓｅｑuenceofzerobitｓｉｎthelowestbｉtsofapointeｒ.ﻫ

Whatprobｌemdoeｓｔheｎａmeｓpacefeａtｕｒesｏｌve?Mｕｌtiplｅprovidｅrｓｏflibrariｅsmigｈtusｅｃoｍｍｏnｇlobalidentｉfｉersｃausingａnamecolｌiｓiｏnwheｎａnａｐｐlicatｉoｎｔrｉｅstolinkｗｉｔｈtwoormoｒesuchliｂrarｉｅs．Tｈｅnamespacefeａtuｒesurrouｎdsalｉbraｒy＇sexternaldｅclarａtionswiｔhaｕniｑｕenaｍespａcethａｔeliminates消除thepoｔentｉalforｔhｏsecoｌlisions．naｍeｓpace[ideｎtifiｅr]{ｎaｍespaｃe-body}Anaｍespacedeclaraｔioniｄｅnｔiｆieｓａｎｄaｓsignsanａmetoaｄeｃlaｒａｔivereｇiｏn.

Theidｅnｔifiｅｒinanａmespacedecｌarationｍustbeunｉqueinthedeｃlarativeregioninwhｉｃhitｉsused.Theｉｄenｔiｆｉeristhｅnamｅoftｈｅnaｍespａcｅandisuseｄtoreｆｅreｎceｉtsｍembeｒs.ﻫＷhaｔｉstheuseof'using'deｃｌaratioｎ?Aｕsingdeclaｒａtionmakesitｐossiblｅtｏuｓeanamefroｍaｎａmespaｃewiｔhouｔthescoｐe范围oｐeraｔor.ﻫＷhatｉｓanItｅrａtoｒ迭代器ｃｌasｓ?Ａclａsｓthatｉsuｓedtotｒaversethｒough穿过tｈeｏbｊecｔsｍaiｎtainedbyacｏnｔainerｃlass.Thereａrｅfiｖecａtｅgoｒiｅsofiｔeraｔｏｒｓ:ｉnpｕｔｉteｒators,ｏutpｕtｉteｒaｔors，ｆｏrwardiｔｅｒatoｒs，bidirectionaｌitｅｒaｔors,randｏmaccess.Anｉteratorisaｎenｔitytｈatgivesaｃｃeｓｓtotｈecontenｔsofacontainerobjectｗiｔhoutvｉolaｔｉｎｇencapsｕｌaｔionｃonstraints.Ａccesstothｅconｔenｔsisｇｒantedｏnaone-ａt-ａ-timebasisinｏrｄer．Theoｒdｅｒcanbeｓtｏraｇｅｏrdｅr（asinlｉｓｔｓandqueues)orsoｍearｂitrａrｙｏｒder(asinarｒａｙｉndicｅs)ｏｒacｃordingｔosｏｍeoｒderingrｅlａtｉon(aｓｉnａnorderedｂinarytree）．Tｈeiｔeratorｉsaconｓtrｕcｔ,whiｃhproｖidesaｎinterfacethａt,whencａllｅd,yieldsｅithｅrthｅnｅxteｌemeｎtintｈecｏntaineｒ，orsｏｍevaluedeｎotingthefacttｈａttｈereaｒｅnoｍoreｅlemenｔstoexamiｎe.Iｔeratoｒshidetｈedｅtailsｏfａccesｓｔoaｎｄuｐｄateofｔheeleｍentsofａcontａineｒcｌass.Somethingｌikｅａpｏiｎter.

Whaｔｉsaｄanｇlｉng悬挂poiｎter?Adangliｎgpointｅrarｉsｅｓwhenyouuｓｅｔheａｄdressｏｆaｎoｂｊectａfterｉtsliｆetｉmeisover．Thｉsmayoｃｃurinｓitｕatiｏnslikｅreｔｕrｎingaｄdreｓsesｏｆtheaｕtomatiｃvaｒiablesｆromaｆuｎｃtionｏruｓiｎgｔheａddｒesｓoｆthｅｍemoｒyｂｌｏｃkafｔeｒitisfrｅed.ﻫWｈaｔdoｙoｕmeanbｙStackｕnwindｉng？Itisapｒocｅsｓｄuｒｉngｅxｃeｐtｉｏnｈanｄlingwhenthedestructoｒisｃaｌledfｏｒalllocaloｂjecｔｓｉnthestackbeｔweeｎtheplacewｈｅreｔheexｃeｐtｉonwasthrｏwnanｄwhereitｉｓcａughｔ.ﻫ抛出异常与栈展开(stackｕnwinｄinｇ)抛出异常时，将暂停当前函数的执行,开始查找匹配的catcｈ子句。一方面检查throw自身是否在try块内部,假如是,检查与该try相关的cａtch子句，看是否可以解决该异常。假如不能解决，就退出当前函数，并且释放当前函数的内存并销毁局部对象,继续到上层的调用函数中查找，直到找到一个可以解决该异常的cａtｃh。这个过程称为栈展开（staｃｋuｎｗiｎdinｇ）。当解决该异常的ｃatch结束之后，紧接着该catch之后的点继续执行。1.为局部对象调用析构函数如上所述，在栈展开的过程中，会释放局部对象所占用的内存并运营类类型局部对象的析构函数。但需要注意的是,假如一个块通过neｗ动态分派内存，并且在释放该资源之前发生异常,该块因异常而退出，那么在栈展开期间不会释放该资源,编译器不会删除该指针，这样就会导致内存泄露。2.析构函数应当从不抛出异常在为某个异常进行栈展开的时候，析构函数假如又抛出自己的未经解决的另一个异常,将会导致调用标准库tｅrminate函数。通常ｔeｒminate函数将调用aｂort函数,导致程序的非正常退出。所以析构函数应当从不抛出异常。3.异常与构造函数假如在构造函数对象时发生异常，此时该对象也许只是被部分构造,要保证可以适当的撤消这些已构造的成员。4．未捕获的异常将会终止程序不能不解决异常。假如找不到匹配的catcｈ，程序就会调用库函数teｒmiｎａtｅ。Namethｅｏperatoｒsthａtcannｏtbeｏｖｅrloaded?？sizeof,．,.*,.->，::,？:

Whａｔiｓacontaiｎｅrclａss？Whａtareｔhetypｅsoｆｃonｔainerclａsses?Ａcontaｉnｅrｃlａssiｓaclａssthatｉsｕseｄtｏhｏlｄｏbjectsｉnｍemoryorｅxtｅｒnalstｏragｅ．Ａｃonｔaineｒclassaｃｔsasagenericｈoldｅr.Ａcontaｉｎeｒｃlａsshasａｐrｅdefiｎedbeｈaviｏrandawell－knownｉnterｆaｃe.Aｃontａinerclassisａsｕpｐoｒtｉngclaｓｓwhoseｐurposeｉstohidｅtｈetoｐｏｌogｙusedformａinｔainｉngthｅｌistoｆobjecｔsinmｅｍoｒy．Wｈeｎacontainerclａsscｏntaｉｎsaｇｒoｕpofmiｘedobjecｔs,theｃｏｎtaｉnｅrisｃallｅdaｈeterogeｎeｏuｓ不均匀的多样的cｏntａiｎer;ｗｈenｔhｅconｔaｉnerｉｓholdｉngaｇｒｏupoｆｏbjecｔｓtｈataｒｅaｌltｈesａｍe,thｅcｏｎtainｅriscallｅｄaｈｏｍｏｇenｅouｓ单一的均匀的container．

Wｈaｔｉsinｌｉnefuncｔion?？Tｈｅ__inｌinekｅyｗorｄtelｌsｔhecomｐiｌeｒtosuｂstｉtuｔe替代ｔhecodeｗithiｎthefunctiｏｎdeｆinｉｔioｎforeveryinstanｃeofaｆuncｔioｎcａｌｌ.Ｈowevｅｒ,suｂstｉtutioｎocｃｕｒｓonlyatthecompiｌer'sdｉｓcｒetion灵活性．Ｆoreｘａmple,thecompilerdoesnotiｎｌinｅafunctionｉｆiｔsａddreｓsｉstａkｅnoriｆitisｔoｏｌａrｇetoｉnlｉｎe.ﻫ使用预解决器实现，没有了参数压栈，代码生成等一系列的操作,因此,效率很高,这是它在C中被使用的一个重要因素

Whａtisovｅrlｏａdｉng?？WiththeＣ++lａnｇuaｇe,ｙoｕｃanｏveｒloadfunctｉoｎsandoｐeratｏrｓ.Overloadingｉｓtheｐraｃｔicｅofsuｐpｌyiｎgｍｏｒｅtｈaｎonedefiniｔiｏnｆoragiｖenfｕnctionｎａmeintｈesamesｃoｐe.－Aｎｙｔwofunctioｎsiｎaseｔｏfoverlｏadeｄfuｎcｔiｏnｓmuｓtｈavedifｆerｅntargumenｔlｉsｔs.

-Overloadinｇfunｃtiｏｎswiｔhargｕmeｎtｌistｓofthesamｅｔypeｓ,basedonreturntｙpealonｅ,isａｎerrｏr.ﻫ

ＷｈatisOverriｄing?Tooｖｅrriｄｅａmｅthod,asubclａssofthｅclasｓthaｔoriｇiｎaｌｌydeclａrｅdthｅmetｈoｄmustdeclａrｅamｅtｈodwitｈthｅsamｅname,returntyｐｅ（orａsuｂｃlassofthａtretuｒntypｅ）,andｓaｍｅparamｅｔerliｓt.

Thedefinitｉonofthemｅｔhｏdovｅrｒidingｉs:

·Mｕｓtｈaveｓamemｅthodname.ﻫ·Muｓｔhaveｓamedataｔyｐe.ﻫ·Ｍusthavesameａrgumeｎｔliｓt.ﻫＯverridinｇameｔｈｏdmeａｎstｈatreplacｉｎｇaｍethodｆunctｉｏnａlｉtyiｎchilｄcｌasｓ.Tｏｉmplｙoverｒｉdingfuｎｃtionalｉｔywenｅｅdｐaｒｅntａndchildclａsses．Iｎｔheｃhｉldclasｓyouｄｅfiｎｅtｈeｓamｅｍethodｓignatureaｓonedｅfｉnedｉｎthepareｎtclass.ﻫWｈatis"this"poｉnter?Ｔhethispointeriｓapｏinteｒaｃcessｉｂleｏｎlywithinｔｈemeｍbｅrfunctｉｏnｓｏfaclass,struct,ｏrｕnｉoｎtｙpe.Itpointstotｈeobjectfoｒwhｉchthemeｍbｅｒfunｃｔｉｏniscallｅd.Staticmemｂerfunctionsdonothavｅathispointｅr.Wｈenanon-statiｃmｅmbeｒｆunｃｔionｉsｃaｌlｅｄforanobjｅcｔ，theaddressoｆｔheoｂjecｔispasｓｅdaｓaｈiddenargumenttｏthefｕnctｉoｎ．Foreｘampｌe，theｆｏllowingfｕｎｃｔｉoncallmyDate.seｔMonｔh(3);ｃａｎbｅiｎtｅｒpreｔｅd解释thisway：seｔMonｔh(＆ｍyDａtｅ，3);Theobject'saｄdｒｅsｓｉsavaiｌablefｒomwiｔhｉnthemｅmberｆunctionasthethｉspointer.Iｔiｓlegal，tｈougｈunneｃｅｓsary,ｔouｓetｈｅthispointｅｒwheｎrｅｆerringｔomeｍｂerｓoｆtheclass.ﻫWhａthaｐpｅｎswhenyｏuｍａkecall"delｅtethis;"？?Thｅcodehastｗobuilt-ｉnpiｔfaｌls陷阱/误区.Fiｒst，ifiｔｅxｅcutesiｎamembｅｒfｕncｔionｆoranｅｘｔern,static,orautｏｍatiｃobject,thepｒogｒａmｗｉlｌpｒobablycrashasｓoｏnasthedｅｌetｅsｔatemｅｎtexecutｅs.Theｒｅｉｓnoporｔablｅwａyforａnobｊecttoteｌｌthatｉｔwaｓinｓtantiatedonｔhｅheap，soｔheclaｓｓcannotasserｔthatiｔsｏbjｅｃｔispropeｒlyiｎsｔanｔiａted.Seconｄ,ｗheｎanobjectcｏｍmitｓsｕｉcidethisｗaｙ,ｔheｕｓiｎgproｇrａmmightnｏｔknｏwaboｕtｉtsdemisｅ死亡/转让.Asfarastheinｓtanｔiatinｇprogrａｍiｓｃonｃerned有关的,tｈｅobjｅctremａiｎsiｎscｏｐｅanｄcontinｕｅstoｅxistｅｖｅnthoｕgｈｔｈeoｂjectdiditselfiｎ.Suｂseｑuent后来的dｅｒｅferencing间接引用（ｄereｆeｒｅnｃingｐoiｎteｒ

重引用指针,dereｆerenｃingoperａtoｒ

取值运算符)ofthepoinｔercananduｓuallydoesleａdtodｉｓaster不幸.Youshouｌdｎeveｒdotｈiｓ．Sinｃeｃomｐileｒdoesｎｏｔkｎowwhethertheｏｂjeｃtwasallｏcａｔｅｄｏnthｅstａckｏrｏnｔheｈｅap,"delｅtetｈiｓ"couｌdcaｕseａdｉsaster.

Howvirtualfｕncｔｉonｓａrｅiｍplementeｄ执行C＋＋?Virtuaｌfｕnctｉoｎsaｒeiｍpleｍeｎｔｅdusingａtaｂleofｆｕnctionpoｉnteｒs,calledthｅｖｔａｂle.Thereisoneenｔryintｈetabｌepｅrvirtuaｌfunctiｏｎｉntｈｅclａss．Thiｓtabｌeiｓcreatedｂyｔhｅconsｔrucｔｏrofｔheclaｓs.Ｗhenaderiｖｅdclassiｓconsｔructeｄ,itsbaseclａssｉscｏｎstructeｄfirｓtwhichｃreateｓthevtabｌe.Ifｔhｅｄeｒivｅｄcｌassoｖｅｒrｉｄesａｎyofthebaｓecｌassesｖirtｕalfunctiｏｎs,thｏｓeentriesiｎｔｈevtａbｌｅarｅｏverwritｔenbyｔhｅderiｖedclaｓscｏnstrｕcｔor．Thisiｓwhyyoushoulｄnevｅrcallvirｔualｆunctiｏnsfromａconstructor:becａｕｓetｈevtabｌeｅntriesforｔｈｅｏbｊｅctmaynotｈaｖeｂｅenｓetupbythｅderiveｄcｌasscｏｎstruｃtoｒyet,soyｏumiｇｈtｅndupcallｉnｇbａｓｅｃlassimplementationsｏfthosevｉrｔualfuncｔionｓﻫWhａtｉsｎａmemaｎglｉnginC++??Tｈepｒｏcｅssoｆeｎcodingｔｈeparamｅtｅrtypeｓwｉthtｈefｕnｃｔioｎ/metｈodnameｉntoauniｑuenａｍeisｃallednaｍemaｎgliｎg.Ｔheinverseprocｅｓｓiｓcalleddeｍanglｉｎg.ＦorexampleFoo:：bａr(int,long)ｃｏｎstisｍangｌｅｄas`bar__C3Fooｉl＇.

Forａcoｎstrｕctoｒ,ｔｈｅｍｅthodｎamｅislｅftｏut．ＴhａｔisFｏo::Ｆoo(iｎt,long)consｔismaｎｇlｅｄａs`__C3Fooiｌ'.

Ｗhatｉsthediｆferenｃｅbeｔwｅｅnａpoiｎterａｎdaｒeferencｅ?Aｒefereｎcｅmusｔalｗａyｓreｆertoｓomeｏbjｅｃtanｄ,thｅreｆoｒｅ,ｍustalｗaysbeiｎitiaｌiｚed;poｉntersdｏnothａvesuchｒestricｔionｓ.Apoｉntercａnbeｒｅａｓｓignｅdtopointtｏｄｉfferentoｂｊｅｃtswｈｉleaｒeferenｃeａｌwａysrefeｒstoanobｊeｃｔｗitｈwhicｈitwaｓiniｔiａｌizeｄ．Howaｒeprefiｘanｄpostfixversionsｏfoperatoｒ++()diffｅrenｔiaｔed？Thｅｐｏstfｉxveｒsｉonoｆoｐerａtor++()ｈasaduｍｍypａrameteｒｏftｙpeｉnt.Thｅprefiｘverｓｉondoeｓｎotｈavedｕmmｙparamｅter．Wｈatisthｅdiffeｒｅｎcebｅtｗeenｃonsｔcｈaｒ*mｙＰｏｉｎterandchａr*constmyPoｉｎter?Ｃｏnｓtchar*myPoｉnｔeriｓanonconｓtantpoｉnｔｅrｔoconstaｎｔdaｔa；wｈｉｌechaｒ*constmyＰｏiｎtｅｒisacｏｎstantpointeｒtonｏncｏnsｔanｔdata.HowcａnIhandlｅaｃｏnstruｃtorthaｔfails?throwanｅxceｐtiｏｎ.Construｃtorｓdｏn'thavearｅtｕrｎｔype，soit＇snoｔpossibletｏuｓereｔurnｃoｄｅs.Ｔｈeｂeｓｔwayｔｏsignalconｓtrｕctorｆailｕｒeistｈｅreforetothroｗａnexception.ＨowcanIhａnｄlｅadestｒｕｃｔorｔhａtfaｉls?Ｗriｔeａmessａｇｅtoａｌog-fｉlｅ.Buｔｄonotthｒowaｎｅxceｐtioｎ．ﻫTheC++ruleistｈａｔｙｏumuｓｔnｅｖerthroｗanｅxｃｅptioｎfromadeｓtｒuctoｒｔhatｉsbｅingcallｅddｕringtｈe＂stackunｗinding"procesｓofanｏtherexｃeｐtion.Forｅxamｐｌｅ,ifｓomeoｎｅsａysthrowFｏo(),tｈeｓｔackwillbeunｗｏundsoallthesｔackfraｍesbｅtweｅnｔhethrowＦoｏ()ａｎdtｈｅ}catch(Ｆｏoe)｛wｉllgeｔpoppｅｄ．Thisiscalledsｔackｕnｗindｉng.ﻫDuriｎgsｔaｃkunwindiｎg，alｌｔｈｅloｃalobjｅｃｔｓinaｌｌthosｅsｔackframesａrｅdeｓtrucｔeｄ.Ｉfonｅofｔhosｅdｅstｒｕｃtorsthｒoｗsａｎｅｘcｅpｔioｎ（ｓayｉｔthｒowsaBaｒobjｅct),theＣ+＋runtimｅsyｓｔemｉsinano-wｉnsituaｔｉon：sｈouｌdｉtignoretheBarandeｎduｐinthe｝caｔch(Fooｅ){wｈｅreｉtwasｏrｉginallｙheadeｄ？ＳhoｕldｉtiｇnoreｔｈｅＦoｏanｄｌｏｏkfora}catch(Bａre){ｈaｎｄleｒ?Ｔhｅreisnｏgoodaｎｓwer--eithercｈoiｃｅloseｓiｎforｍation.

ＳoｔheC++languagｅguａranteestｈatitwiｌlcａlｌtｅrmｉnatｅ(）ａttｈiｓpoint，andｔｅrmｉｎate()kilｌｓｔｈeprocesｓ.Baｎgyｏｕ＇redead.

WhatisVirtualDesｔructor?

Usｉngvｉrtuａldｅｓtｒｕctoｒｓ,ｙｏucａｎdｅｓtｒoｙobｊｅｃtｓｗithｏuｔknowinｇｔheiｒtｙpｅ-ｔｈｅcoｒｒecｔdestructorfｏrtheobjeｃtｉsｉnｖokeｄusingｔhevirtualfunctionｍｅchanｉsｍ．Ｎotethatｄestructorscanalsobeｄeclareｄaspureｖirｔuaｌfunctionsｆorａbsｔractclａｓses．ｉfsomeonｅwillderiveｆｒｏｍyouｒｃlass,aｎｄiｆsoｍｅｏnｅwilｌｓａy"ｎeｗDeｒｉvｅd＂,whｅre＂Derivｅｄ"isderｉvedfrｏmｙourclａss,andifｓｏｍeoｎeｗillsaydeｌｅｔep,whｅreｔheａｃtｕalobjeｃt＇stypeis"Derｉved"bｕtthepoｉｎtｅrp＇stypeiｓyouｒcｌass．ﻫ

Caｎyouthiｎkｏfasituａtionｗhereyoｕｒｐrｏｇrａｍwｏuldcraｓhwiｔｈｏutｒeaｃｈingthebreakpoiｎｔwhichyousetａtｔhebegｉnniｎgoｆmａiｎ（)?C＋+ａllowsfordynamｉciｎiｔiａlizatiｏnｏfgｌobalｖariablesbeｆoreｍain（）isiｎｖｏked.Itisposｓibｌｅthatiniｔｉaｌiｚatｉonｏｆglobａlwiｌｌinvokesｏmｅfｕnｃtｉon.Iftｈisｆｕnctｉoｎcｒａshesｔhecｒasｈwillocｃurbeforｅmaiｎ(）iｓentereｄ.ﻫNaｍeｔwoｃaseｓwhereｙouMUSTuseｉnitｉalizationlistaｓｏppoｓedｔoａssｉgnmentinｃonstrｕcｔors.Boｔｈnon-staｔｉccｏnstdａtamemberｓａndrｅfｅrencｅｄatamemｂｅrｓcaｎnotbeaｓsignedｖaｌｕes;insｔead，yoｕshoulｄｕｓeinitialiｚaｔiｏnｌisｔｔoiniｔiaｌiｚetｈｅm.

Ｃaｎyouovｅrlｏaｄaｆｕnｃtionbａsedonlyｏnwｈeｔheraparametｅriｓavalueorarefｅｒｅｎce?No.Passingｂyvalueaｎdbyreferencelooksｉdenｔｉcaltoｔｈecaｌlｅr.

WｈaｔａrｅthedifferencｅsbetｗeenａC+＋strucｔandＣ++clasｓ?Ｔｈedefauｌtmｅmberandbasecｌａｓsaccｅsssｐｅcifｉers标记符aredｉｆfereｎt．ThｅC++struｃtｈａsalltheｆｅatｕrｅsｏｆｔheｃlasｓ．Theonｌｙdifｆeｒeｎｃesarｅｔｈａtａstｒuctｄeｆaｕｌtstｏｐublicｍｅmｂeｒａccessaｎdpublicｂaseclａsｓinheritance,aｎdaclassdefａuｌtsｔｏthepriｖaｔeａccｅssspecifｉeraｎdｐrivatｅbaｓeclasｓｉnheritance．ﻫWhaｔdoesｅxｔeｒｎ"C＂intfｕnｃ（int＊,Foo)ａcｃoｍｐlisｈ实现/达成／完毕？Itwilｌturnoff＂ｎamemaｎｇling"fｏrfuncｓｏtｈatｏnecａnｌinktoｃodｅcoｍpilｅdbyａＣcomｐｉｌer.

Howdoyｏｕａcceｓstheｓｔatｉcｍeｍｂｅrｏfaclass？<ClassNａme＞:：<SｔaticMemberＮａｍe>ﻫWｈatｉsmultiｐlｅinhｅｒｉtaｎcｅ(vｉrtualiｎheritance)?Whataｒeiｔsadvantaｇesaｎｄdｉｓadｖaｎｔages?ＭultipｌeInhｅriｔanｃｅistheｐrｏｃeｓswhｅrｅby通过achildcanbedｅrivｅdfｒoｍｍoｒethanｏnepaｒentcｌａss.Theａdvantａgeofmｕｌtipleiｎherｉtａnceｉstｈａtitallowｓaclaｓstoinheｒitthｅfuｎｃtiｏnａlｉty功能ofｍｏrethanoｎｅbaｓe