C函数、数组、指针和调试器gdb--指针

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1、C函数、数组、指针和调试器gdb—指针Thatexplicitlyindicatesthatthecurrentpointerdoesnotpointtoanyvariable・Forpointers,therearetwooperatorsassociatedwiththem,asfollows・&takeaddressoperator・*:takethevalueofthememorycellpointedtobythepointer・Theuseofpointers4to8cases#ineludeInt,main(

2、)Inta=100,B=200;Int*pl二&a,*p2=&b;Printf（〃%d〃,〃％d〃，〃a〃，〃B〃）；Printf（〃%d〃,〃％d〃，〃*pl〃，‘'*p2〃）;Printf（〃％x〃，〃％x〃，〃&b〃）；Printf（〃％x〃，〃％x〃，〃P1〃，〃卩2〃）；*pl=*pl*3;Printf（〃％d〃，a）;Printf（〃％drT,*pl）;Printf（〃％x〃，&a）;Printf（〃％x〃，Pl）;Pl二&b;Printf（〃％x〃，Pl）;Printf（〃％x

3、〃，P2）;Return0;}Theprogramrunsasfollows:OnehundredthousandandtwohundredOnehundredthousandandtwohundredBff59be0,bff59bdcBff59be0,bff59bdcThreehundredThreehundredBff59be0Bff59be0Bff59bdcBff59bdcProgramdescription:(1)theprogramfirstdefinestwopointers,Pl,P2,respectively,pointin

4、gtovariablesAandB.Thefirst,secondlinesoftheprogramoutputarethesamebecausethevaluesobtainedby*Pland*P2arethevaluesofthevariablestheypointto.(2)thethirdlineisthattheyoutputthevariablea,B'saddressinsixteendecimalform,andthefourthlineoutputsthevaluesofpointervariablesPl,p2・Var

5、iablePl,P2storestheaddressofthevariabletheyarepointingto.Plstoresthememoryaddressofthevariablea,andtheP2storesthememoryaddressofthevariableB.Thus,theresultsofthethirdand4stalksarethesame・(3)statement*Pl二*P1*3,firstobtainthepointerPlreferstothevariablevalue,thatis,100,after

6、3,theresultsaresavedtothePlpointofthevariable,atthistimethevariableavaluefrom100to300.Therefore,theprogramsixth,7linesoutput300.Thenexttwovariables,theaddressoftheAandthevalueofthePl,areprintedout,andthetwovaluesarethesameasthosewithouttheexecutionof*Pl二*Pl*3statements・(4)

7、thestatementPl二B,theaddressofthevariableBtothepointervariablePl,thenPlandP2pointtothevariableB,thetwopointervariabledhwyisavariableBmemoryaddress,theprogramoutputisconsistentwiththelasttwolines・Three,pointersandarraysInC,pointersarecloselyrelatedtoarrays.Thearraynameisactu

8、allythepointertothefirstelementofthearray.Seetheprogrambelow:Inta[]二{2,4,6,&10};Int*pl二a;