Debug It!: Find, Repair, and Prevent Bugs in Your Code

by Paul Butcher

Overview

Some developers thrash around aimlessly looking for a bug without concrete results. Others have the knack of unerringly zeroing in on the root cause of a bug. Are they geniuses? Just lucky? No, they've learned the secrets of professional debugging. This book will equip you with the tools, techniques and approaches-proven in the crucible of professional software development-to ensure that you can tackle any bug with confidence.

You'll learn how to handle every stage of the bug life-cycle, from constructing software that makes debugging easy, through detection, reproduction, diagnosis and rolling out your eventual fix.

If you develop software, sooner or later you're going to discover that it doesn't always behave as you intended. Working out why it's misbehaving can be hard. Sometimes very hard. Debug It! is here to help!

All bugs are different: there is no silver bullet. You've got to rely upon your intellect, intuition, detective skills and yes, even a little luck. But that doesn't mean that you're completely on your own-there is much you can learn from those who have gone before. This book distills decades of hard-won experience gained in the trenches of professional software development, giving you a head-start and arming you with the tools you need to get to the bottom of the problem, whatever you're faced with.

Whether you're writing Java or assembly language, targeting servers or embedded micro-controllers, using agile or traditional approaches, the same basic bug-fixing principles apply. From constructing software that is easy to debug (and incidentally less likely to contain bugs in the first place), through handling bug reports to rolling out your ultimate fix, we'll cover the entire life-cycle of a bug.

You'll learn about the empirical approach, which leverages your software's unique ability to show you what's really happening, the importance of finding a reliable and convenient means of reproducing a bug, and common pitfalls so you can avoid them. You'll see how to use commonly available tools to automatically detect problems before they're reported by customers and how to construct "transparent software" that provides access to critical information and internal state.

Product Details

ISBN-13:	9781934356289
Publisher:	Pragmatic Bookshelf
Publication date:	11/28/2009
Series:	Pragmatic Programmers
Pages:	232
Product dimensions:	7.40(w) x 8.90(h) x 0.90(d)

About the Author

Paul Butcher started out writing games for 8-bit home computers before he was a teenager, and since then has worked in diverse fields at all levels of abstraction, from microcode on bit-slice processors to high-level declarative programming and all points in between. He's been using agile approaches for the last several years, although had adopted many of the same techniques before the agile movement gave them a name. Paul's depth of experience derives from a history of working for startups in which he's had the privilege of working with several great teams on cutting edge technology.



In an attempt to demonstrate that he's at least as fast as Lewis Hamilton, Paul totaled his race-car last year. So no more playing with expensive toys for the time being-but he will be back on track soon!

Table of Contents

Preface xi

About This Book xi

Acknowledgments xii

I The Heart of the Problem 1

1 A Method in the Madness 3

1.1 Debugging Is More Than "Making the Bug Go Away" 3

1.2 The Empirical Approach 5

1.3 The Core Debugging Process 6

1.4 First Things First 7

1.5 Put it in Action 11

2 Reproduce 13

2.1 Reproduce First, Ask Questions Later 13

2.2 Controlling the Software 15

2.3 Controlling the Environment 16

2.4 Controlling Inputs 18

2.5 Refining Your Reproduction 26

2.6 What If You Really Can't Reproduce It? 35

2.7 Put It in Action 38

3 Diagnose 39

3.1 Stand Back-I'm Going to Try Science 39

3.2 Stratagems 46

3.3 Debuggers 52

3.4 Pitfalls 53

3.5 Mind Games 57

3.6 Validate Your Diagnosis 62

3.7 Put it in Action 63

4 Fix 65

4.1 Clearing the Decks 66

4.2 Testing 67

4.3 Fix the Cause, Not the Symptoms 69

4.4 Refactoring 71

4.5 Checking in 73

4.6 Get Your Code Reviewed 74

4.7 Put it in Action 75

5 Reflect 77

5.1 How Did it Ever Work? 77

5.2 What Went Wrong? 78

5.3 It'll Never Happen Again 81

5.4 Close the Loop 84

5.5 Put it in Action 85

II The Bigger Picture 87

6 Discovering That You Have a Problem 89

6.1 Tracking Bugs 89

6.2 Working with Users 94

6.3 Working with Support Staff 99

6.4 Put it in Action 101

7 Pragmatic Zero Tolerance 103

7.1 Bugs Take Priority 103

7.2 The Debugging Mind-Set 106

7.3 Digging Yourself Out of a Quality Hole 108

7.4 Put it in Action 113

III Debug-Fu 115

8 Special Cases 117

8.1 Patching Existing Releases 117

8.2 Backward Compatibility 118

8.3 Concurrency 123

8.4 Heisenbugs 125

8.5 Performance Bugs 127

8.6 Embedded Software 129

8.7 Bugs in Third-Party Software132

8.8 Put it in Action 137

9 The Ideal Debugging Environment 139

9.1 Automated Testing 139

9.2 Source Control 142

9.3 Automatic Builds 147

9.4 Put it in Action 155

10 Teach Your Software to Debug Itself 157

10.1 Assumptions and Assertions 157

10.2 Debugging Builds 167

10.3 Resource Leaks and Exception Handling 172

10.4 Put it in Action 179

11 Anti-patterns 181

11.1 Priority Inflation 181

11.2 Prima Donna 182

11.3 Maintenance Team 184

11.4 Firefighting 186

11.5 Rewrite 187

11.6 No Code Ownership 189

11.7 Black Magic 189

11.8 Put it in Action 190

A Resources 193

A.1 Source Control and Issue-Tracking Systems 193

A.2 Build and Continuous Integration Tools 196

A.3 Useful Libraries 198

A.4 Other Tools 200

B Bibliography 205

Index 207