dangle是什么意思（DanglingPointersinC++）

DanglingPointersinC++

DanglingpointersinC++cancausesomeseriousbugsinyourcode.Inthisarticle,wewillexplorewhatdanglingpointersareandhowtoavoidthem.

WhatareDanglingPointers?

Adanglingpointerisapointerthatpointstoamemorylocationthathasbeendeallocatedorfreed.Whenaprogramfreesupablockofmemory,itreturnstheblocktotheoperatingsystem.However,thepointerstillpointstothesamelocationinmemorywhereanewvaluecanbestored.Ifyoutrytoaccessorchangethismemorylocation,thebehavioroftheprogramisundefinedandcanresultinaruntimeerrororacrash.

HowtoIdentifyDanglingPointers?

Identifyingdanglingpointerscanbedifficult,especiallywhenitiscausedbyunintendedbehavior.Herearesomecommonscenarioswheredanglingpointerscanhappen:

• WhenyoudeleteablockofmemorythatapointerispointingtowithoutsettingthepointertoNULLoranewaddress.
• Whenyoupassapointertoafunctionthatdeallocatesthememorypointedtobythatpointer.
• Whenyouuseapointerthathasgoneoutofscopeorhasbeenuninitialized.

Toavoidthesescenarios,youcanuseafewtechniquessuchassettingpointerstoNULLafteryouhavedeletedthem,avoidingpassingpointerstofunctionsthatcannotguaranteethatthememorytheypointtowillremainvalid,andinitializingpointersbeforeuse.

HowtoAvoidDanglingPointers?

HerearesomebestpracticestoavoiddanglingpointersinyourC++code:

• Avoiddeletingthesamememoryblocktwice.Thiscancauseruntimeerrorsandcrashes.
• SetpointerstoNULLafterdeletingthemtopreventthemfrombecomingdanglingpointers.
• Donotpasspointerstofunctionsthatcandeallocatememorypointedtobythem.
• Avoidusingpointersthathavegoneoutofscope.
• Initializeallpointersbeforeuse.

Inconclusion,danglingpointersinC++cancausememoryissuesthatcancrashyourprogram.Beawareofhowyouusepointersinyourprogramandbecarefulwhenfreeingmemory.Byfollowingthesebestpractices,youcanavoidthepitfallsofdanglingpointersandhaveamorestableprogram.