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COMP3131/9102: Programming Languages and Compilers

Jingling Xue

School of Computer Science and Engineering

The University of New South Wales

Sydney, NSW 2052, Australia

http://www.cse.unsw.edu.au/~cs3131

http://www.cse.unsw.edu.au/~cs9102

Copyright @2018, Jingling Xue

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Bonus Assignment

• Deadline: 3 June 2018

• Worth: 5 marks

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Timetable

• Lectures:

Week 12: this lecture

Week 13: no lecture (Working on Assn 5)

• Tutorials:

Week 12: on

Week 13: no tutorial

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Lecture 11: Java Class File Format & Runtime Areas

1. Timetable

2. Class file format (Sun’s JVM Spec Book)

3. Runtime areas (JVM Spec & Bill Venners’ Inside the JVM book)

4. Java bytecode verification

5. Revision

6. PhD topics

7. Final exam

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Lvalue v.s. Rvalue

• Question: are the following legal in C, Java and C++?

++i = 1; i++ = 1; (i=j) = 1;

• Consider

int i = 5;

i = i + 1;

add the rvalue 5 and 1 and

store 6 into lvalue 2000

2000

memory

5

rvalue

lvalue(address)

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Example 1: Test.java

class Test {

public static void main(String argv[]) { }

}

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Example 1: Java Class File (Output of od -An -tx1 Test.class)

ca fe ba be 00 03 00 2d 00 0f 07 00 0b 07 00 0d

0a 00 02 00 04 0c 00 07 00 05 01 00 03 28 29 56

01 00 16 28 5b 4c 6a 61 76 61 2f 6c 61 6e 67 2f

53 74 72 69 6e 67 3b 29 56 01 00 06 3c 69 6e 69

74 3e 01 00 04 43 6f 64 65 01 00 0f 4c 69 6e 65

4e 75 6d 62 65 72 54 61 62 6c 65 01 00 0a 53 6f

75 72 63 65 46 69 6c 65 01 00 04 54 65 73 74 01

00 09 54 65 73 74 2e 6a 61 76 61 01 00 10 6a 61

76 61 2f 6c 61 6e 67 2f 4f 62 6a 65 63 74 01 00

04 6d 61 69 6e 00 20 00 01 00 02 00 00 00 00 00

02 00 00 00 07 00 05 00 01 00 08 00 00 00 1d 00

01 00 01 00 00 00 05 2a b7 00 03 b1 00 00 00 01

00 09 00 00 00 06 00 01 00 00 00 01 00 09 00 0e

00 06 00 01 00 08 00 00 00 19 00 00 00 01 00 00

00 01 b1 00 00 00 01 00 09 00 00 00 06 00 01 00

00 00 03 00 01 00 0a 00 00 00 02 00 0c

• The classfile format defined in the Sun’s JVM spec book

• BCEL’s listclass useful for understanding the constant pool

• Generated using Java 45.3

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Example 1: Test.class Annotatedca fe ba be magic

00 03 minor version

00 2d major version

00 0f constant pool count-------------------- constant pool table --------------------------07 00 0b07 00 0d0a 00 02 00 040c 00 07 00 0501 00 03 28 29 5601 00 16 28 5b 4c 6a 61 76 61 2f 6c 61 6e 67 2f 53 74 72 69 6e 67 3b 29 5601 00 06 3c 69 6e 69 74 3e01 00 04 43 6f 64 6501 00 0f 4c 69 6e 65 4e 75 6d 62 65 72 54 61 62 6c 6501 00 0a 53 6f 75 72 63 65 46 69 6c 6501 00 04 54 65 73 7401 00 09 54 65 73 74 2e 6a 61 76 6101 00 10 6a 61 76 61 2f 6c 61 6e 67 2f 4f 62 6a 65 63 7401 00 04 6d 61 69 6e-------------------- end of constant pool table --------------------------

00 20 access_flags

00 01 this_class

00 02 super_class

00 00 interfaces_count

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00 00 fields_count

00 02 methods_count

------------------ <init> ---------------------------------------00 00 access_flags00 07 name_index00 05 desc_index00 01 attr_count00 08 attr_name_index00 00 00 1d attr_length00 01 max_stack00 01 max_locals00 00 00 05 code_length2a b7 00 03 b1 code00 00 exception_table_length00 01 attr_count00 09 LineNumberTable00 00 00 06 attr_length00 01 line_number_table_length00 00 start_pc00 01 line_number------------------ end of <init> ---------------------------------

------------------------------ main -----------------------------00 09 access_flags00 0e name_index00 06 desc_index00 01 attr_count00 08 attr_name_index00 00 00 19 attr_length00 00 max_stack00 01 max_locals00 00 00 01 code_length

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b1 code00 00 exception_table_length00 01 attr_count00 09 attr_name_index00 00 00 06 attr_length00 01 line_number_table_length00 00 start_pc00 03 line_number------------------------------ end of main ------------------------00 01 attr_count00 0a attr_name_index00 00 00 02 attr_length00 0c sourcefile_index

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Example 1: Test.class Annotated (java listclass -code

-constants Test.class, where listclass is from BCEL)class Test extends java.lang.Object

filename Test.class

compiled from Test.java

compiler version 45.3

access flags 32

constant pool 15 entries

ACC_SUPER flag true

Attribute(s):

SourceFile(Test.java)

2 methods:

void <init>()

public static void main(String[])

1)CONSTANT_Class[7](name_index = 11)

2)CONSTANT_Class[7](name_index = 13)

3)CONSTANT_Methodref[10](class_index = 2, name_and_type_index = 4)

4)CONSTANT_NameAndType[12](name_index = 7, signature_index = 5)

5)CONSTANT_utf8[1]("()V")

6)CONSTANT_Utf8[1]("([Ljava/lang/String;)V")

7)CONSTANT_Utf8[1]("<init>")

8)CONSTANT_Utf8[1]("Code")

9)CONSTANT_Utf8[1]("LineNumberTable")

10)CONSTANT_Utf8[1]("SourceFile")

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11)CONSTANT_Utf8[1]("Test")

12)CONSTANT_Utf8[1]("Test.java")

13)CONSTANT_Utf8[1]("java/lang/Object")

14)CONSTANT_Utf8[1]("main")

void <init>()

Code(max_stack = 1, max_locals = 1, code_length = 5)

0: aload_0

1: invokespecial java.lang.Object.<init> ()V (3)

4: return

Attribute(s) =

LineNumber(0, 1)

public static void main(String[])

Code(max_stack = 0, max_locals = 1, code_length = 1)

0: return

Attribute(s) =

LineNumber(0, 3)

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Java Runtime Areas

1. pc registers

2. Java stacks (due to multi-threading)

• Local variables

• Operand stack

• Frame data

– pointer to constant pool

– information about method return

– · · ·3. Method Area

4. Heap

All JVM diagrams are from Bill Venner’s Inside the JVM book

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Internal Architecture of JVM

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Method Area and Heap

• Arrays are objects

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Java Stacks – One Per Thread

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Stack Frame

• A new stack frame is created for every method invocation

• Stack frame consists of:

– Local variables (lectures 9 & 10)

– Frame data

– Operand stack (lectures 9 & 10)

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One Possible Implementation of a Java Frame

LocalVariables

FrameData

OperandStack

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Example 2: gcd.vc

int i = 5;

int j = 2;

// find the greatest common divisor of two integers

int gcd(int a, int b) {

if (b == 0)

return a;

else

return gcd(b, a - (a/b) *b);

}

int main() {

putIntLn(gcd(i, j));

}

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Example 2: gcd.java

import VC.lang.System;

public class gcd {

static int i = 5;

static int j = 2;

public gcd() { }

int gcd(int a, int b) {

if (b == 0)

return a;

else

return gcd(b, a - (a/b) *b);

}

public static void main(String argv[]) {

gcd vc$;

vc$ = new gcd();

System.putIntLn(vc$.gcd(i, j));

}

}

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Example 2: gcd.j.class public gcd

.super java/lang/Object

.field static i I

.field static j I

; standard class static initializer

.method static <clinit>()V

iconst_5

putstatic gcd/i I

iconst_2

putstatic gcd/j I

; set limits used by this method

.limit locals 0

.limit stack 1

return

.end method

; standard constructor initializer

.method public <init>()V

.limit stack 1

.limit locals 1

aload_0

invokespecial java/lang/Object/<init>()V

return

.end method

.method gcd(II)I

.limit stack 5

.limit locals 3

.var 0 is this Lgcd; from Label1 to Label2

.var 1 is a I from Label1 to Label2

.var 2 is b I from Label1 to Label2

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Label1:

.line 10

iload_2

ifne Label0

.line 11

iload_1

ireturn

Label0:

.line 13

aload_0

iload_2

iload_1

iload_1

iload_2

idiv

iload_2

imul

isub

invokevirtual gcd/gcd(II)I

Label2:

ireturn

.end method

.method public static main([Ljava/lang/String;)V

L0:

.var 0 is argv [Ljava/lang/String; from L0 to L1

.var 1 is vc$ Lgcd; from L0 to L1

new gcd

dup

invokenonvirtual gcd/<init>()V

astore_1

aload_1

getstatic gcd/i I

getstatic gcd/j I

invokevirtual gcd/gcd(II)I

invokestatic VC/lang/System/putIntLn(I)V

L1:

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; The following return inserted by the VC compiler

return

; set limits used by this method

.limit locals 2

.limit stack 3

.end method

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Reading

• Class file format (Sun’s JVM Spec Book)

• Runtime areas (JVM Spec & Bill Venners’ Inside the JVM

book)

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Lecture 11: Java Class File Format & Runtime Areas

1. Timetable√

2. Class file format (Sun’s JVM Spec Book)√

3. Runtime areas (JVM Spec & Bill Venners’ Inside the JVM book)√

4. Java bytecode verification

5. Revision

6. PhD topics

7. Final exam

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ByteCode Verification

• Loop

while (true) 1;

• Bytecode:

iconst_1

pop

• Removing pop causes a Java.VerifyError:

Exception in thread "main" java.lang.VerifyError: (class: x,

method: foo signature: (V) Inconsistent stack height 1 != 0)

• JVM Spec:

If an instruction can be executed along several different execution paths, the

operand stack must have the same depth (2.6.2) prior to the execution of the

instruction, regardless of the path taken.

https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#

jvms-4.10.1.4

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The VC Compiler

Source Code (Test.vc)

Assignment 1: Scanner

Assignment 2a & 2b: Parser

Assignment 3: Semantic Analyser

Assignment 4: Code Generator

Jasmin Assembly Code (Test.j)

Jasmin Assembler

Java Virtual Machine

Results

VC

.lan

g.S

yst

em.c

lass

Tokens

AST

Decorated AST

Java Byte Code (Test.class)

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Scanning

• Theory:

– Regular expressions (i.e., regular grammars)

– Finite automata (DFAs and NFAs)

• Writing a scanner

– Hand coding

– Scanner generator (JLex and JavaCC)

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Thompson’s Construction (Cont’d): Slide 79

N(r)

N(s)S A

ǫ

ǫ

ǫ

ǫ

RE r|s : start

S N(r) AN(s)start

RE rs :

N(r)S Aǫ ǫ

ǫ

ǫ

startRE r

∗ :

RE (r) : N((r)) is the same as N(r)

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False RE r∗ Rule

S N(r) T

ǫ

ǫ

startRE r

∗ :

• The FA constructed using this rule may not be correct.

• Try (a∗b)∗!

• The ǫ edges in Thompson’s construction ensure that the

construction is correct, and are removed when the NFA is

converted to a DFA

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Parsing

• Theory:

• Context-free grammars

• First, Follow and Select sets

• Writing a parser

• Recursive-descent

• Table-driven LL(1)

• Parser generators (JavaCUP and JavaCC)

LR(k) not covered this year

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Context-Sensitive Analysis

• Theory:

• Attribute grammars

• Evaluation of attributes

• Scoping

• Type rules

• Writing a context-sensitive analyser

• Identification: Relate the use of an identifier to its

declaration

• Type Checking: Enforce the language’s type rules

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Code Generation

• Theory:

• Syntax-directed translation

• Code templates

• Writing a code generator

• JVM

• Jasmin assembly language

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PhD Projects

• Some current PhD projects:

– Compiler techniques for heterogeneous architectures (CPUs +

TPUs/GPUs/FPGAs)

– Concurrent programming (e.g., programming model and OO)

– Program analysis for safety and security

• PhD topics

– Languages and compilers for multicore computing (e.g., GPUs)

– Language safety and security

– Compilers for asymmetrical multicores

– Security analysis of Android apps

– Static and dynamic analysis for bug detection

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Final Exam

• 2 hours, closed

• 6 questions

• The papers and solutions for 2000 – 2003 available:

1. Login to a CSE computer

2. Type:

cp ~cs3131/Exams/past-exams.zip your-directory

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Remember to Complete

myExperience Survey for

COMP3131/9102

Good luck with your studies!

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