Who. Winter Compiler Construction Generic compiler structure. Mailing list and forum. IC compiler. How

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1 Winter Comiler Construction Mooly Sagiv and Roman Manevich School of Comuter Science Tel-Aviv University Who Roman Manevich Schreiber Oen-sace (basement) Tel: Wednesday 16:00-17:00 htt:// 2 Mailing list and forum Mailing list web interface: htt://listserv.tau.ac.il/archives/cs html htt://listserv.tau.ac.il/archives/cs html htt://listserv.tau.ac.il/archives/cs html Activate by going to: htts:// Forwarding, changing address: htts:// htt:// Not registered? Mail to listserv@listserv.tau.ac.il with the line: subscribe CS X Real Name where X is your recitation course number (2/3/4) Forum: htt:// Generic comiler structure Comiler txt Source text Frontend (analysis) Semantic Reresentation Backend (synthesis) 3 4 comiler How txt Source text Frontend (analysis) Comiler Semantic Reresentation Backend (synthesis) rog.ic Program Lexical Syntax Analysis Analysis JFlex JavaCu AST Symbol Inter. Table Re. etc. (IR) Java Code Generation rog.s assembly ic Program Lexical Analysis Syntax Analysis AST Symbol Table etc. Inter. Re. (IR) Code Generation cutable rog.s assembly GNU assembler rog.o libic.a (libic + gc) GNU linker rog. 5 scrit / Ant 6 1

2 Grading and schedule 45% 50% exam 5% theoretical assignment 50% roject 4 assignments + 1 bonus different weights checked both automatically and manually teams tentative schedule PA1 PA2 PA3 PA4 PA5 24/10 31/10 23/1 30/1 6/2 13/2 20/2 27/2 5/3 12/3 19/3 26/3??/????/????/????/????/????/?? today 7/3 14/3 oll semester ends exam 7 Project guidelines Teams of 2 or 3 students me before next recitation Subject: Comilation - new roject team List of members (first name, last name, id, username on nova) Team-account user name In case of doubt ask questions in the forum There is adequate time to comlete assignments Start early and lease follow directions 8 Today Language ic Lexical Syntax AST Symbol Analysis Analysis Table etc. Goals: language overview See language secification Inter. Code Re. Generation (IR) Understand the scoe of the roject 9 language - main features Strongly-tyed Primitive tyes for int, boolean, string Reference tyes Object oriented Objects, virtual method calls Inheritance Memory management Dynamic hea allocation of obejcts and arrays Automatic deallocation (garbage collection) Runtime safety checks Null dereference Division by 0 Array access out of bounds Many things are left out Short imlementation time Adated with ermission from Prof. Radu Rugina (Cornell University) 10 Unsuorted features Access control Everything is ublic Interfaces Downcasting Method overloading (but still allow overriding) Excetions Packages Multile source files 11 rogram structure Program is sequence of class definitions Class is sequence of fields and methods Static methods and virtual methods Exactly one main method static void main(string[] args) {... Variables can be declared anywhere in a method Check initialization before use Strings are rimitive tyes Arrays T[], T[][] 12 2

3 tyes Every class is a tye Primitive tyes: int : 1,-1,2,-2, boolean : true, false string : hello References : null Arrays : int [] x = new int[5]; x.length==5; All variables must be declared comiler infers tyes for exressions Tye-safety Well-tyed rograms do not result in runtime tye errors 13 Subtying Inheritance induces subtying relation Tye hierarchy gives acyclic grah (forest) Subtying rules: A extends B { A B B C A B A A A C null A Subtying does not extend to array tyes A subtye of B then A[] is not a subtye of B[] 14 Exressions Objects Exression language Every exression has a tye and a value Loos: while (exr) {stmt Conditionals: if (exr) stmt else stmt Arithmetic oerators: + - / % Relational comatison: < > == <= >= Logical oerators: && Unary oerators:! - Assignment: x = exr 15 Instances of classes are objects int x; // initialized to 0 new Point() allocates object of class Point on hea and initializes fields No arguments An object can be thought of as a struct (record) with a slot for each field 16 Methods int x; -- close method -- close class A class can also define methods to maniulate fields Methods can refer to the current object using this Examle class TestPoint { Point ; Point q; boolean test() { = new Point(); q =.(1,2); return ==q; int x; q this

4 Method imlementation Each object knows how to access method As if object contains slot ointing to the In reality imlementations save sace by sharing these ointers among instances of the same class methods Inheritance examle We can extend oints to colored oints: class ColoredPoint extends Point { int color; color = 0; 0 x y color Method invocation and inheritance Methods are invoked by disatch Understanding disatch in the resence of inheritance is a subtle asect of OO languages Point ; = new ColoredPoint();.(1,2); has static tye Point has dynamic tye ColoredPoint. invokes ColoredPoint imlementation Method invocation Examle: invoke method.(a+b,20/2) 1. Evaluate 2. Find class of 3. Find of 4. Evaluate arguments a+b,20/2 5. Bind to this 6. Bind actual arguments to formal arguments 7. Run method memory management Memory allocated every time new is used Memory deallocated automatically by reclaiming unreachable objects Done by a garbage collector (GC) Use off-the-shelf GC a = b a unreachable object b b a 23 Library functions libic rovides: I/O oerations datatye conversions system level-oerations class Library { static void rintln(string s); // rints string s followed by a newline. static void rint(string s); // rints string s. static void rinti(int i); // rints integer i. static void rintb(boolean b); // rints boolean b. static int readi(); // reads one character from the inut. static string readln(); // reads one line from the inut. static boolean eof(); // checks end-of-file on standard inut. static int stoi(string s, int n); // returns the integer that s reresents // or n of s is not an integer. static string itos(int i); // returns a string reresentation of i. static int[] stoa(string s); // an array with the ascii s of chars in s. static string atos(int[] a); // builds a string from the ascii s in a. static int random(int i); // returns a random number between 0 and n-1. static int time(); // number of milliseconds since rogram start. static void exit(int i); // terminates the rogram with exit n. 24 4

5 For next week Slit into teams Send me with team members and reresentative account Read language secification htt:// Get acquainted with Java J2SE 1.5 (or higher) Eclise IDE More helful links on web-site See you next week