东南大学 编译原理 教学教案 Cp7.ppt

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1、Chapter7RuntimeEnvironmentsZhaiYuqingZhouXiaoyuProgramvsProgramExecutionAnexecutionofaprogramiscalledasaprocess.Aprogramconsistsofseveralprocedures(functions).Anexecutionofaprogramwouldcausetheactivationoftherelatedprocedures.AllocationandDe-allocationofDataObjectsAname(e.g

2、,avariablename)inaprocedurewouldberelatedtodifferentdataobjects.Anactivationmaymanipulatedataobjectsallocatedforitsuse.BindingsofNamesWhenanenvironmentassociatesstoragelocationswithanamex,wesaythatxisboundtos;theassociationitselfisreferredtoasabindingofx.Abindingisthedynamic

3、counterpartofadeclaration.DataObjectEveneachnameisdeclaredonceinaprogram,thesamenamemaydenotedifferentobjectsatruntime.The“dataobject”correspondstoastoragelocationthatcanholdvalues.EnvironmentandStateInprogramminglanguagesemantics,theterm“environment”referstoafunctionthatmap

4、sanametoastoragelocation,andterm“state”referstoafunctionthatmapsastoragelocationtothevalueheldthere.EnvironmentandStateenvironmentstatenamestoragevalueEnvironmentandStateAnassignmentchangesthestate,butnottheenvironment.AllocationandDe-allocationofDataObjectsManagedbytherun-t

5、imesupportpackage.Therepresentationofadataobjectatruntimeisdeterminedbyitstype.Ifxisnotofabasictype,thestoragesforxmaybeacollectionofmemorywords.FactorsthatDeterminestheRunTimeEnvironmentofaProgramRecursivecallofprocedures.Localnamestoragespaceallocationstrategy.globalnamest

6、oragespaceallocationstrategy.Parameterpassingmechanism.FactorsthatDeterminestheRunTimeEnvironmentofaProgramwhetherafunctionisallowedtobeaparameteroforreturnvalueofafunction.SubdivisionofRuntimeMemoryTypicalsubdivisionofruntimememoryintocodeanddataareascodeStaticdatastackheap

7、Thegeneratedtargetcode;Dataobjects;Acounterpartofthecontrolstacktokeeptrackofprocedureactivations;StorageAllocationStrategiesStorageAllocationStrategiesStaticallocation.Laysoutstorageforalldataobjectsatcompiletime.Stackallocation.Managestherun-timestorageasastack.Heapallocat

8、ion.Allocatesandde-allocatesstorageasneededatruntimefromaheap.RestrictionsG