3.2 Translation of Object-Oriented Language Constructs

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1 Content of Lecture Compilers and Language Processing Tools Summer Term 2011 Prof. Dr. Arnd Poetzsch-Heffter Software Technology Group TU Kaiserslautern c Prof. Dr. Arnd Poetzsch-Heffter 1 1. Introduction 2. Syntax and Type Analysis 2.1 Lexical Analysis 2.2 Context-Free Syntax Analysis 2.3 Context-Dependent Analysis 3. Translation to Target Language 3.1 Translation of Imperative Language Constructs Selected Aspects of Compilers 4.1 Intermediate Languages 4.2 Optimization 4.3 Data Flow Analysis 4.4 Register Allocation 4.5 Code Generation 5. Garbage Collection 6. XML Processing (DOM, SAX, XSLT) c Prof. Dr. Arnd Poetzsch-Heffter 2 Section Outline 3.2 Translation of Object-Oriented Language Constructs c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 3 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language Concepts of Object-Oriented Programming Languages c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 5 Example: Object-Oriented Language Concepts Beispiel: (objektorientierte Sprachkonzepte) class Person { String name; Person( String n, int gd ) { name = n; gebdatum = gd; public void drucken() { System.out.println("Name:"+ this.name); System.out.println("Geb:"+ this.gebdatum); boolean hat_geburtstag ( int datum ) { return (this.gebdatum%10000) == (datum%10000); class Student extends Person { int matrikelnr; int semester; c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 7 Student(String n,int gd,int mnr,int sem) { super( n, gd ); matrikelnr = mnr; Beispiel: (objektorientierte Sprachkonzepte) We consider a class-based language and use Java as an example. class Person { Important String Concepts: name; Classes int and gebdatum; Object Creation /* in der Form JJJJMMTT */ Encapsulation Person( String n, int gd ) { Subtyping name and = n; Inheritance Dynamic gebdatum Method = Binding gd; public void drucken() { System.out.println("Name:"+ this.name); System.out.println("Geb:"+ this.gebdatum); boolean hat_geburtstag ( int datum ) { return (this.gebdatum%10000) == Concepts of Object-Oriented (datum%10000); Programming Languages c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 6 Example: Object-Oriented Language Concepts (2) class Student extends Person { int matrikelnr; int semester; Student(String n,int gd,int mnr,int sem) { super( n, gd ); matrikelnr = mnr; semester = sem; public void drucken() { super.drucken(); System.out.println( "Mnr:"+ matrikelnr); System.out.println( "Sem:" + semester); A. Poetzsch-Heffter, TU Kaiserslautern 254 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 8

2 Example: Object-Oriented Language Concepts (3) class Test { public static void main( String[] argv ) { int i; Person[] pf = new Person[3]; pf[0] = new Person( "Meyer", ); pf[1] = new Student("M\"uller", ,758475,5); pf[2] = new Student("Planck", , ,47); for( i = 0; i<3; i = i+1 ) { pf[i].drucken(); Das Beispiel zeigt Klassen, Objekterzeugung, The Vererbung example demonstrates (mit Subtyping classes, und object Spezialisierung) creation, inheritance sowie (with subtyping and specialization) and dynamic method binding. dynamisches Binden von Methoden. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language Umsetzung mit prozeduralen Sprachen Anhand des obigen Beispiels erläutern wir die Translation grundlegenden Schemes: Übersetzungsschemata: Klassen, Classes, Klassentypen class types record! Verbundtypen, types, pointer types Zeigertypen Object creation Allocation of dynamic variables/objects Objekterzeugung! Allokation dyn. Variablen/Objekte Methods, constructors procedures Methoden, Dynamic binding Konstruktoren Use of procedure! Prozeduren pointers with selection of record components dyn. Bindung! Verwendung von Prozedurzeigern We illustrate these schemes at the above example. The considered mit Selektion von Verbundkomponenten target language is C. Als Übersetzung Zielsprache verwenden der Typen wir und hier Methoden: C. Basisdatentypen von Java! Basisdatentypen von z.b. int A. Poetzsch-Heffter, nach TU int Kaiserslautern 255 boolean nach int ( typedef int boolean; ) c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 11 Implementation Referenztypen von of Example Java! Zeigertypen in C von C z.b. String nach String* Person nach Person* wobei String und Person in C geeignete Verbundtypen Fields sind. arewir realized betrachten by record die types: Implementierung von Person: typedef struct sperson Person; struct sperson { String* name; void (*drucken)( Person* ); boolean (*hat_geburtstag)( Person*, int ); ; Methoden werden als Prozeduren realisiert: void Person_drucken( Person* this ) { printf("name:%s\n", this->name ); printf("geb:%d\n",this->gebdatum); c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 13 Implementation boolean Person_hat_geburtstag of Example in C (3) (Person* this,int datum){ return (this->gebdatum%10000)==(datum%10000); Constructors are realized as procedures: Konstruktoren werden als Prozeduren realisiert: A. Poetzsch-Heffter, TU Kaiserslautern 256 Person* PersonK( String* n, int gd ) { Person* this = (Person*) malloc( sizeof(person) ); this->name = n; this->gebdatum = gd; this->drucken = Person_drucken; this->hat_geburtstag = Person_hat_geburtstag; Übersetzung von Vererbung/Spezialisierung: Bzgl. der Verbundkomponenten wird Vererbung im Wesentlichen durch Duplikation realisiert: c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 15 typedef struct sstudent Student; struct sstudent { String* name; c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 10 Translation of Types and Methods Basis Übersetzung data types of der Java Typen basis und data Methoden: types of C, for example: Basisdatentypen int int von Java! Basisdatentypen von boolean int z.b. int nach int (typedef int boolean;) boolean nach int Reference types of Java pointer types of C, for example: ( typedef int boolean; ) String String* Referenztypen Person Person* von Java! Zeigertypen von C where String z.b. andstring Person are nach record types String* C. Person nach Person* wobei String und Person in C geeignete Verbundtypen sind. Wir betrachten die Implementierung von Person: typedef struct sperson Person; struct sperson { String* name; c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 12 Implementation void (*drucken)( of Example Person* in C (2) ); boolean (*hat_geburtstag)( Person*, int ); ; Methods Methoden are realized werden by procedures: als Prozeduren realisiert: void Person_drucken( Person* this ) { printf("name:%s\n", this->name ); printf("geb:%d\n",this->gebdatum); boolean Person_hat_geburtstag Konstruktoren werden als Prozeduren (Person* this,int realisiert: datum){ return (this->gebdatum%10000)==(datum%10000); Person* PersonK( String* n, int gd ) { Person* this = (Person*) malloc( sizeof(person) ); A. Poetzsch-Heffter, TU Kaiserslautern 256 this->name = n; this->gebdatum = gd; this->drucken = Person_drucken; this->hat_geburtstag = Person_hat_geburtstag; c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 14 Translation of Inheritance and Specialization Übersetzung von Vererbung/Spezialisierung: Inheritance Bzgl. with der respect Verbundkomponenten to record components wird Vererbung is realized by duplication: im Wesentlichen durch Duplikation realisiert: typedef struct sstudent Student; struct sstudent { String* name; void (*drucken)( Student* ); boolean (*hat_geburtstag)( Student*, int ); int matrikelnr; int semester; ; Type conversions Zu beachten ist die notwendige Typanpassung beim impliziten it Argument for implicit in arguments der Unterklasse. of subclass are necessary. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language A. Poetzsch-Heffter, TU Kaiserslautern 257

3 Translation of Inheritance and Specialization (2) Bzgl. der Methoden lässt sich Vererbung ohne InheritanceCodeduplikation with respect to umsetzen; methods die can Methoden be realized der without code duplication. Oberklasse Methods lassen of superclass sich nach can geeigneter be reused after appropriate type conversion. Typkonvertierung unverändert verwenden: Student* StudentK (String* n,int gd,int mnr,int sem ) { Student* this = (Student*) malloc(sizeof(student)); this->name = n; this->gebdatum = gd; this->matrikelnr = mnr; this->semester = sem; this->drucken = Student_drucken; this->hat_geburtstag = (boolean(*)(student*,int)) Person_hat_geburtstag; this->semester = sem; this->drucken = Student_drucken; this->hat_geburtstag = (boolean(*)(student*,int)) Person_hat_geburtstag; Translation of Inheritance and Specialization (3) Spezialisierung wird durch zusätzliche Attribute (s.o.) Specialization und neue is realized Prozeduren by additional realisiert, attributes die and ggf. procedures die that may call überschriebenen overridden methods: Methoden aufrufen: void Student_drucken( Student* this ) { Person_drucken( (Person*)this ); printf("mnr:%d\n", this->matrikelnr ); printf("sem:%d\n", this->semester ); A. Poetzsch-Heffter, TU Kaiserslautern 258 Spezialisierung wird durch zusätzliche Attribute (s.o.) und neue Prozeduren realisiert, die ggf. die überschriebenen Methoden aufrufen: c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 17 Translation of Object Creation & Method Invocation void Übersetzung Student_drucken( von Objekterzeugung Student* this und ) { Person_drucken( (Person*)this ); Methodenaufruf: printf("mnr:%d\n", this->matrikelnr ); printf("sem:%d\n", this->semester ); Object creation Objekterzeugung corresponds entspricht to call einem of the Konstruktoraufruf ; constructor. Method invocation Methodenaufruf is realized wird durch byselektion selection und and call of method belonging Aufruf to the der object zum Objekt gehörenden Methode realisiert. A. Poetzsch-Heffter, TU Kaiserslautern 258 void main( String* argv[] ) { int i; Person* pf[3]; pf[0] = PersonK( "Meyer", ); pf[1] = (Person*) StudentK("M\"uller", ,758475,5); pf[2] = (Person*) StudentK("Planck", , ,47); for( i = 0; i<3; i = i+1 ) { pf[i]->drucken( pf[i] ); c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 18 Translation of Object Creation & Method Invocation (2) Note the duplicate reference to the target object in a "method call". Dynamic binding is realized by usage of procedure pointers. Remarks: Record components are not "inherited" and have to be re-listed for each subclass. No usage of superclass constructor Explicit type conversion necessary Direct pointers to methods of an object use needlessly much memory. Dynamic binding only requires dereferencing which is almost as efficient as an ordinary procedure call. Zu beachten ist die doppelte Angabe des Zielobjekts beim Methodenaufruf. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 19 Dynamische Bindung wird also durch Verwendung von Prozedurzeigern erreicht. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language A. Poetzsch-Heffter, TU Kaiserslautern Classes declare: attributes (in Java: fields) constructors methods In the following, we consider a language that supports only single inheritance (cf. Java), i.e., each class (except Object) has exactly one superclass. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 21 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 22 Object Layout Object Layout (2) Objects are handled as memory areas on the heap: Each object of class C gets a variable (object state) for each inherited and for each attribute declared in C. Additionally, it gets a variable for referring to information about the class and its methods. As object identity, often the start address of the memory area is used (or another appropriate address). Example: Beispiel: (Objektlayout) private int a2; Object Objektreferenz Reference class: a2: Klassen- Class and & Methoden- Information zu for Klasse Class A As for records, attribute instances/instance variables are addressed by a relative address (offset) with respect to the object reference. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 23 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 24

4 Object Layout (3) Object Layout (4) The size of the instance variables depends on their type. In Java, int and float variables require 4 bytes, long and double variables require 8 bytes. private int a2;... class B extends A { int b;... Klassen- Class and & Methoden- Information zu for Klasse Class C class C extends B { int c; Object Objektreferenz Reference class: a2: b: c: c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 25 Object Layout (5) The ordering of attribute instances is important to allow for subtyping: Each subclass object can be placed in all positions where a superclass object is expected. Thus, the attribute instances of the superclass have to have the same relative addresses in all sub- and superclass objects. Remarks: Bemerkungen: In the above example, Im obigen we have Beispiel not haben considered wir Attributinstanzen attribute instances der of the class Object. Klasse Object vernachlässigt Private attribute instances Private Attributinstanzen of superclasses von Oberklassen have to bemüssen present in all instances of subclasses: auch in Instanzen von Unterklassen vorhanden sein: private int a2; int m() { return a2; class B extends A { int b; int n() { return m(); Zur Klassen- und Methodeninformation siehe unten. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 26 Die Reihenfolge der Attributinstanzen ist wichtig, um Subtyping zu Translation ermöglichen: of Classes Jedes Unterklassen-Objekt muss überall dort eingesetzt werden können, wo ein Oberklassen- Objekt erwartet wird. Example: Access to Subclass Objects A avar = new B();... a.avar.a2... Deshalb müssen die Attributinstanzen der Oberklasse in Ober- und Unterklasse-Objekten die gleiche Relativadresse besitzen A. Poetzsch-Heffter, TU Kaiserslautern 263 The relative address of a2 has to be independent of the dynamic type of avar. The dynamic type of a reference-typed expression E in a state S is the type of the object that is obtained by evaluating E in the state S. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 27 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 28 Alternative Object Layout Alternative Object Layout (2) In some cases, also an object descriptor is used. Here, the example of a C object: Objektreferenz Object Reference Deskriptor Descriptor class: Klassen- Class and & Methoden- Information zu for Klasse Class C a2: b: c: Remarks: Pros: all object descriptors have the same memory requirements memory block for instance variables can be more easily moved (simplifies for instance garbage collection) Cons: more memory per object additional dereferencing step for accessing instance variables c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 29 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 30 Class Information Example: Introspection in Java The content (and the extend) of the class information depends on the language. Three typical examples: Class information is not provided at runtime. Class information contains all information required for dynamic type conversion : A avar = new b(); B bvar = (B) avar; Class information is represented by an object that allows introspection (requesting class information at runtime) and reflection (modifying the program at runtime). Java supports introspection by using objects of the class Class. For each type in a Java program, there exists one object of the class Class. The class Class contains amongst others: the static method forname the instance method getname c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 31 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 32

5 Beispiel: (Introspektion in Java) Java unterstützt Introspektion mittels Objekten der Klasse Class. Für jeden Typ eines Java-Programms gibt es ein Objekt der Klasse Class. Die Klasse Class Translation of Object-Oriented besitzt Language unter Constructs anderem: die statische Methode forname die Instanzmethode getmethod Example: Introspection in Java (2) import java.lang.reflect.*; Realization of Methods public class Inspektor { public static void main(string[] ss) { try{ Class klasse = Class.forName( ss[0] ); Method[] methoden = klasse.getmethods(); for( int i = 0; i < methoden.length; i++ ){ Method m = methoden[i]; Class rettype = m.getreturntype(); String methname = m.getname(); Class[] partypes = m.getparametertypes(); System.out.print(retType.getName() t ett pe + " " + methname+"(" ); for( int j = 0; j < partypes.length; j++ ){ if( j > 0 ) System.out.print(", "); System.out.print( partypes[j].getname() ); System.out.println( ");" ); catch( ClassNotFoundException e ) { System.out.println("Klasse "+ ss[0]+" fehlt"); Method information allows accessing methods belonging to an object: It provides the data structure for realization of dynamic binding. In class-based languages, all objects of a class have the same methods; thus, method information of all objects of a class can be stored together. (more memory-efficient compared to realization by procedures) A. Poetzsch-Heffter, TU Kaiserslautern 266 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 33 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 34 Virtual Method Table Virtual Method Table (2) Classically, method information is stored in a virtual method/functions table. (For simplicity, class information is not shown) Alle all A-Objekte objects Es existiert int a2; also für jede Klasse teilen genau share sich mtab eine mtab Methodentabelle. int m() {... Der Zeiger auf die Methoden- tabelle int wird n( int vom i Konstruktor ) {... gesetzt. Die Methodentabelle enthält Zeiger auf die A::m Object Objektreferenz Reference Methodenimplementierungen. A::n mtab: Die Technik ermöglicht Subtyping, da die Relativ- adressen von Oberklasse-Methoden so gewählt a2: werden können, dass sie in Ober- und Unterklasse gleich sind. Die Technik ermöglicht Überschreiben durch Ausstausch des entsprechenden Eintrags (s. Beispiel) c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 35 Method Overriding Beispiel: (Überschreiben von Methoden) mtab: int a2; int m() {... int n( int i ){... a2: class B extends A { int b; mtab: int m() {... void p() {... a2: b: A::m A::n B::m A::n B::p For each class, there exists exactly one method table. The pointer to the method table is set by the constructor. The method table contains pointers to the method implementations. This technique allows for subtyping, as the relative address of the subclass methods can be chosen such that there are the same addresses in super- and subclasses. It further allows method overriding by changing the according method entry. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 36 Method Overriding (2) Adressierung einer Methode jeweils indirekt über Methodentabelle und Relativadresse: A method is addressed indirectly by the method table and the relative address: A avar = new A();... avar.m()... // M[avar.mtab]+RA(m)! A::m... avar.n(7)... // M[avar.mtab]+RA(n)! A::n A avar = new B();... avar.m()... // M[avar.mtab]+RA(m)! B::m... avar.n(7)... // M[avar.mtab]+RA(n)! A::n A. Poetzsch-Heffter, TU Kaiserslautern 268 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 37 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 38 Method Overriding (3) Realization Wie bei den ofinstanzvariablen Constructors gewährleistet die richtige Reihenfolge der Einträge in der Methodentabelle, dass auf ein Unterklassen-Objekt wie auf ein Oberklassen-Objekt zugegriffen werden kann. As for instance variables, the correct ordering of the entries in the method table allows that a subclass object can be accessed in the same way as a superclass object. Overriding methods are selected automatically, if applicable. Constructors Dabei werden are realized automatisch by procedures. überschreibende Source language Methoden semantics typically ausgewählt, requires the sofern following vorhanden. for object of class C: Allocation of memory of the new C object Recursive calls of the superclass constructors Execution of the called constructor of C Potentially: class loading, initialisation of variables A. Poetzsch-Heffter, TU Kaiserslautern 269 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 39 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 40

6 Multiple Inheritance The translation technique considered so far can only be used for languages with single inheritance. In this section, we sketch the concept of multiple inheritance the problems associated with multiple inheritance Multiple inheritance exists, for instance, in C++ or Eiffel. With multiple inheritance, a class can inherit from several classes. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 41 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 42 Multiple Inheritance (2) Example: Beispiel: (Mehrfachvererbung) In folgendem Klassendiagramm erbt E mehrfach: Difficulties of Multiple Inheritance B k1 k2 C k5 A k3 k4 D k2 k3 Does E inherit the attributes of A twice, i.e., does it contain two copies of each component? (only relevant for attributes) How are name conflicts resolved? (E inherits two components with name k2.) How can E objects be realized such that they can be used as A, B, C or D objects in the same way? E k6 Problematik: Soll E die Attribute von A doppelt erben, d.h. von jeder Komponente zwei Kopien besitzen? (nur relevant im Zusammenhang mit Attributen) c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 43 Difficulties of Multiple Inheritance (2) Wie sollen Namenskonflikte aufgelöst werden? ( E erbt zwei Komponenten mit Namen k2) Assuming, E inherits Mit welchen twicetechniken from A, können an object E-Objekte contains so realisiert the following Unter der Annahme, dass E von A doppelt erbt, components: besitzt werden, ein E-Objekt dass sie auch die als folgenden A-, B-, C- Komponenten: und D-Objekte auftreten können? A B C D E A. Poetzsch-Heffter, TU Kaiserslautern 271 B::k1 B::k2 A::k3 A::k4 C::k5 A::k3 A::k4 D::k2 D::k3 E::k6 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 44 Difficulties of Multiple Inheritance (3) With the above object layout, E can be used directly as a B object or as a C object, but not as an A or D object. Solutions: Implicit type conversion with modification of the reference into the memory area (Drawback: potentially, problem with object identity) Addressing with class-specific, global relative addresses (cf. Appel) (Drawback: non-modular, complete program has to be known) Mit obigem Komponentenlayout kann ein E-Objekt direkt als B- und C-Objekt Further verwendet Aspects of Object-Oriented werden, Languages nicht aber als A- oder D-Objekt. c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 45 Lösungsansätze: 1. Implizite Typkonvertierung mit Veränderung der Referenz in den Speicherbereich. (Nachteil: ggf. Problem bei Objektidentität) 2. Adressierung mit klassenspezifischen, global verwendbaren Relativadressen (s. Appel). (Nachteil: nicht modular, gesamtes Programm muss bekannt sein) A. Poetzsch-Heffter, TU Kaiserslautern 272 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 46 Static methods Nested classes Virtual classes Encapsulation aspects Dynamic Loading Reflection c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 47 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 48

7 geschachtelte Klassen virtuelle Klassen Kapselungsaspekte dynamisches Laden Reflexion Example: Local Classes Beispiel: (Lokale Klassen) class Outer { Outer w( int j ) { int i = 2; class Local extends Outer { Outer w( int jj ) { System.out.println("i == " +i); System.out.println("j == " +j); System.out.println("j == " + j ); return new Local(); A. Poetzsch-Heffter, TU Kaiserslautern 273 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 49 Literature Example: Local Classes (2) public class LocalClassTest { static public void main(string[] args){ Outer ov = new Outer(); ov.w( 5 ).w( 7 ); ov.w( 7 ).w( 9 ); Gibt es Fehler? Questions: Was ist die Ausgabe und warum? Are there errors? What is the output and why? Lesen Sie zu Abschnitt 3.2: c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 50 Wilhelm, Maurer: Abschnitt 5.2 und Anfang von 5.3 (S ) 195) Appel: Sections , S Recommended Reading: Wilhelm, Maurer: Sect. 5.2 and 5.3. (pp ) Appel: Sect , (pp ) A. Poetzsch-Heffter, TU Kaiserslautern 274 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 51 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 52 A Simple Compiler - The Structure Tools for Compiler Realization Input File (source code) token stream (abstract) syntax tree Scanner Parser Name & Type Analysis Translator Code Generator Output File (target code) attributed (abstract) syntax tree (SL) abstract syntax tree (TL) Scanner: JFlex Parser: ANTLR, JavaCup Abstract Syntax and Attribution for Name and Type Analysis and Translation/Code Generation: Katja c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 53 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 54 Scanner Specification - MiniJava in JFlex Parser Specification - MiniJava in JavaCUP DIGIT = [0-9] LETTER = [a-za-z] %% [ \t\n\r]* { "//" [^\r\n]* (\n \r \r\n) { "/*" [^*] ~"*/" { "class" { return symbol(tokentype.class); "void" { return symbol(tokentype.void); "static" { return symbol(tokentype.static); "int" { return symbol(tokentype.int); "boolean" { return symbol(tokentype.boolean); "return" { return symbol(tokentype.return); "if" { return symbol(tokentype.if); "else" { return symbol(tokentype.else); "while" { return symbol(tokentype.while); c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 55 Statement ::= Block:b {: RESULT = b; : IF:s ParExpression:e Statement:stm {: RESULT = If(sleft, sright, e, stm, Block(-1,-1)); : IF:s ParExpression:e Statement:stm ELSE Statement:estm {: RESULT = If(sleft, sright, e, stm, estm); : WHILE:s ParExpression:e Statement:body {: RESULT = While(sleft, sright, e, body); : RETURN:s Expression:e SEMI {: RESULT = Return(sleft, sright, e); : RETURN:s SEMI {: RESULT = VoidReturn(sleft, sright); : SEMI:s {: RESULT = Block(sleft, sright); : ExpressionStatement:e {: RESULT = e; : ; c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 56

8 Katja Specification for MiniJava Abstract Syntax Implementation of Name Analysis using Katja Statement = Block ( Integer line, Integer column, BlockStatements body ) If ( Integer line, Integer column, Expression cond, Statement thenstmt, Statement elsestmt ) While ( Integer line, Integer column, Expression cond, Statement body ) Return ( Integer line, Integer column, Expression retvalue ) VoidReturn ( Integer line, Integer column ) Assignment ( Integer line, Integer column, Expression left, Expression right ) Expression public static DeclarationPos lookupin final ScopePos scope, final IdentifierPos id) throws CantFind { DeclarationPos result; if (scope == null) throw new CantFind(id); // search in cache if we already made that lookup result = scope.switch(new ScopePos.Switch<DeclarationPos, NE>() { public DeclarationPos CaseBlockStatementsPos (final BlockStatementsPos term) throws NE { c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 57 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 58 Implementation of Name Analysis using Katja (2) Implementation of Name Analysis using Katja (3) public DeclarationPos CaseMethodDeclPos(final MethodDeclPos term) throws NE { for (FormalParameterPos param : term.params()) { if (nameequals(param.ident(), id)) return param; return null; // did not find declaration of id public DeclarationPos CaseClassBodyDeclsPos (final ClassBodyDeclsPos term) throws NE { public DeclarationPos CaseTypeDeclsPos(final TypeDeclsPos term) throws NE { for (TypeDeclPos typedeclpos : term) { if (nameequals(typedeclpos.ident(), id)) return (ClassDeclPos) typedeclpos; return null; // did not find declaration of id ); return result; c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 59 c Prof. Dr. Arnd Poetzsch-Heffter Translation to Target Language 60