东南大学 编译原理 教学教案 Cp6.ppt

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1、Chapter6TypeCheckingZhaiYuqingZhouXiaoyuOverviewStaticCheckingCheckthatthesourceprogramfollowsboththesyntaxand(static)semanticconventionsofthesourcelanguage.ExamplesofStaticCheckTypechecks(incompatibleoperand)Flow-of-controlchecks(breakstatement)Uniquenesschecks(uniquelydeclaredidentifier)Name-r

2、elatedchecksPositionofTypeCheckerAtypecheckerverifiesthatthetypeofaconstructmatchesthatexpectedbyitscontext.Typeinformationgatheredbyatypecheckermaybeneededwhencodeisgenerated.parserTokenstreamTypecheckerSyntaxtreeIntermediatecodegeneratorSyntaxtreeIntermediaterepresentationOverloadAsymbolthatca

3、nrepresentdifferentoperationsindifferentcontextissaidtobe“overloaded”TypeSystemsTypeExpressions(1)(1)Abasictypeisatypeexpression.(2)Atypenameisatypeexpression.(3)Atypeconstructorappliedtotypeexpressionisatypeexpression.Constructorsinclude:Arrays,products,records,pointers,functionsTypeExpressions

4、(2)(4)Typeexpressionsmaycontainvariableswhosevaluesaretypeexpressions.Exampletyperow=recordaddress:integer;lexeme:array[1..15]ofcharend;Record((address*integer)*(lexeme*array(1..15,char)))Examplevarp:rowpointer(row)mod(i,j:int):intint*intintRepresentatypeexpressionbyagraphfunctionf(a,b:char):

5、integerchar*charpointer(integer)TypeSystemsAtypesystemisacollectionofrulesforassigningtypeexpressionstothevariouspartsofaprogram.(1)Atypecheckerimplementsatypesystem.(2)Thetypesystemsarespecifiedinasyntax-directedmanner.StaticandDynamicCheckingofTypesStaticChecking(Donebyacompiler)DynamicChecki

6、ng(donewhenthetargetprogramruns)table:array[0..255]ofchar;i:integer;…table[i]:=‘a’StaticandDynamicCheckingofTypesStronglytypedlanguage(ifitscompilercanguaranteethattheprogramsitacceptswillexecutewithouttypeerror)SpecificationofaSimpleTypeCheckeraSimpleLanguageGrammarfortheSourceLanguagePD;EDD;

7、D

8、id:TTchar

9、integer

10、array[num]ofT

11、TEliteral

12、num

13、id

14、EmodE

15、E[E]

16、ETranslationScheme(1)PD;EDD;DDid:T{addtype(id.entry,T.type)}Tchar{T.type=char}Tinteger{T.type=integer}TranslationScheme(2)Tarray[num]ofT1{T.type=array(1