The debug process constitutes an important part in an app's development cycle. Knowing the (right) tools and techniques means you can optimizes time and therefore costs. In this session we will see a number of techniques to optimize debugging of iOS applications exploiting the power of Xcode, LLDB and other support tools.

1. Advanced iOS Debugging
Massimo Oliviero

2. Massimo Oliviero
Freelance Software Developer
web http://www.massimooliviero.net
email massimo.oliviero@gmail.com
slide http://www.slideshare.net/MassimoOliviero
twitter @maxoly

3. Agenda
‣ Code, some tips for standard functions
‣ Xcode, the best tools for debugging
‣ LLDB, your great friend
‣ Tools, network debugging how to and more
‣ Remote, over the air debugging
‣ Resources, links and videos

4. Source code
Kimera
A simple iOS application for educational purpose
https://github.com/maxoly/Kimera

5. Code

6. It all began...
NSLog(@"Error :( %@", error);
NSLog(@"User: %@", user);
NSLog(@"Array: %@", array);
NSLog(@"URL: %@", url);
NSLog(@"Count: %i", count);NSLog(@"User %@",
user);
NSLog(@"Array %@",
array);
NSLog(@"Error :( %@", error);
NSLog(@"Error :( %@", error
NSLog(@"URL: %@", url);
NSLog(@"Array: %@", array);
NSLog(@"User:
NSLog(@"User: %@", user);NSLog(@"User: %@", user);
NSLog(@"User: %@", user);
NSLog(@"User: %@", user);
NSLog(@"User: %@", user);
NSLog(@"User: %@", user);

7. NSLog
‣ It prints debugs output only to the console
‣ It’s a simple native Foundation function
‣ It’s not too bad, but It’s an ancient technique
‣ It slows things down considerably (if not handled)

8. NSLog optimization
‣ Use convenient macro
‣ Use string conversion functions
‣ Try alternative frameworks

9. #if defined DEBUG
#define MYNSLog(s, ...) NSLog((@"%s [Line %d] " s), __PRETTY_FUNCTION__,
__LINE__, ##__VA_ARGS__)
#else
#define MYNSLog(s, ...)
#endif
-[TestViewController viewDidLoad] [Line 33] message
- (void)viewDidLoad
{
[super viewDidLoad];
MYNSLog(@"message");
}
MyGreatApp-prefix.pch
TestViewController.m
Console
NSLog macro

10. NSLog macro
‣ Enables DEBUG mode output only
‣ Outputs function name and line number
‣ Place macro into .pch file or in a header file
‣ You can use other macros like __ FILE__ (for example)

11. CGPoint point = CGPointMake(10.5f, 12.3f);
NSLog(@"point: %@", NSStringFromCGPoint(point));
AdvanceDebuggingExample[3050:c07] point: {10.5, 12.3}
AdvanceDebuggingExample.m
Console
String conversion functions

12. String conversion functions
‣ NSStringFromCGAffineTransform
‣ NSStringFromCGPoint
‣ NSStringFromCGRect
‣ NSStringFromCGSize
‣ NSStringFromUIEdgeInsets
‣ NSStringFromUIOffset

13. Try alternative framworks
‣ CocoaLumberjack
https://github.com/robbiehanson/CocoaLumberjack
‣ NSLogger
https://github.com/fpillet/NSLogger
‣ DMLogger
https://github.com/malcommac/DMLogger

14. Demo

15. Xcode

16. Xcode
‣ Configure your Behaviors
‣ Print more information with Arguments
‣ Push the limit with Build Settings
‣ Go beyond logging with Breakpoints

17. Behaviors

18. Xcode default
Debugger bar

19. Xcode default Behaviors
VariablesView Console
Debugger
Navigator

20. Xcode Behaviors
‣ Match Xcode to your Workflow
‣ Use Behaviors to control Xcode
‣ Behaviors lets you specify what should happen when a
variety of events occur (like Run)

21. Behaviors
When
pauses
Show Debug Navigator
Show debugger views

22. Change default Behavior
For example, when Running pauses:
‣ show the Breakpoint Navigator instead of Debug
Navigator
‣ show only Variable Views
‣ open another tab only with Console view

23. Demo

24. Arguments

25. Arguments
Product > Scheme > Edit Scheme > Arguments

26. Core Data Logging
-com.apple.CoreData.SQLDebug 1

27. Core Data and iCloud logging
-com.apple.coredata.ubiquity.logLevel 3

28. Build Settings

29. Enable Static Analyzer

30. Treat Warning as Error

31. Warnings

32. Warnings - Objective-C

33. Breakpoints

34. Creating and editing breakpoint

35. Breakpoint Navigator

36. Exception Breakpoint

37. Symbolic Breakpoint

38. Breakpoint Action

39. Breakpoint Action
Condition to evaluateThe num of time to ignore
breakpoint before stoping
Log Message Action
Debugger Command Action
Play sound
Continue program execution

40. Debugger Command Action
po variable
expr (void)NSLog(@”variable: %@”, variable)
breakpoint set -f ADEMasterViewController.m -l 83

41. Sharing Breakpoint
Share breakpoints with the team, so that all can benefit from it
This action will create a new directory to be committed in the repository
AdvanceDebuggingExample.xcodeproj/xcshareddata/

42. Demo

43. LLDB

44. Why LLDB
‣ Consistent Command Syntax
‣ Scriptability with Python
‣ Performance
‣ ...

45. LLDB Commands
print object po [object]
print variable print [variable]
assign value expr [variable] = [value]
(lldb) <command>

46. LLDB Commands
set breakpoint breakpoint set -f [file] -l [line]
load script command script import ~/test.py
evaluate expression expr <expression>
<noun> <verb> [-options [option-value]] [argument [argument...]]

47. Custom Object, the problem
No summary for custom object
@interface KMRMArgument : NSObject
@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) NSDate *detail;
@end
KMRMArgument *argument = [[KMRMArgument alloc] init];
argument.title = @"Debugging";
argument.when = @"Some advance techniques";
Init object
Custom object

48. Custom Summary, the solution
‣ Create a Python script that will instruct LLDB on how to
display a summary of your custom object
‣ Load your Python script via command line or ~/.lldbinit
file

49. Custom Summary
‣ Create“KMRMArgument_summary.py”in Xcode project
‣ Then load script:
(lldb) command script import /path/to/KMRMArgument_summary.py
import lldb
def arg_summary(valobj, internal_dict):
! nameAsString = valobj.GetChildMemberWithName('_name').GetSummary()
! detailAsString = valobj.GetChildMemberWithName('_detail').GetSummary()
! return 'Title: ' + nameAsString + ' - detail: ' + detailAsString
def __lldb_init_module(debugger, dict):
debugger.HandleCommand('type summary add KRMRArgument -F KRMRArgument_summary.arg_summary')

50. Console tips
(lldb) po [self.view recursiveDescription]
$7 = 0x082a2c60 <UITableView: 0x8971000; frame = (0 0; 320 504); clipsToBounds = YES; autoresize = W+H;
gestureRecognizers = <NSArray: 0x8184be0>; layer = <CALayer: 0x8184570>; contentOffset: {0, 0}>
| <UITableViewCell: 0x8282900; frame = (0 176; 320 44); text = '2013-03-12 21:22:34 +0000'; autoresize = W;
layer = <CALayer: 0x8282a30>>
| | <UITableViewCellContentView: 0x8282a60; frame = (0 0; 300 43); gestureRecognizers = <NSArray:
0x8282c30>; layer = <CALayer: 0x8282ac0>>
| | | <UILabel: 0x8282e50; frame = (10 0; 280 43); text = '2013-03-12 21:22:34 +0000'; clipsToBounds
= YES; userInteractionEnabled = NO; layer = <CALayer: 0x8282ee0>>
| | <UIButton: 0x8282c80; frame = (290 0; 30 43); opaque = NO; userInteractionEnabled = NO; layer = ...
(lldb) po [[UIWindow keyWindow] recursiveDescription]
$5 = 0x08273bc0 <UIWindow: 0x8181010; frame = (0 0; 320 568); layer = <UIWindowLayer: 0x81810e0>>
| <UILayoutContainerView: 0xd06eed0; frame = (0 0; 320 568); autoresize = W+H; layer = <CALayer:
0xd071460>>
| | <UINavigationTransitionView: 0xd09e850; frame = (0 0; 320 568); clipsToBounds = YES; autoresize = W
+H; layer = <CALayer: 0xd09e920>>
| | | <UIViewControllerWrapperView: 0x846e160; frame = (0 64; 320 504); autoresize = W+H; layer =
<CALayer: 0x846e210>>
...

51. Demo

52. Tools

53. Tools
‣ Network Link Conditioner
‣ Charles
‣ PonyDebugger
‣ Deploymate
‣ Spark Inspector

54. Network Link
Conditioner

55. Network Link Conditioner
‣ It’s a utility that enables you to simulate network
conditions
‣ To install just select Xcode > Open Developer Tool >
More Developer Tools. You’ll be taken to Apple’s
developer downloads site
‣ Download“Hardware IO Tools for Xcode”

56. Network Link Conditioner

57. Charles

58. Charles Proxy
‣ It’s a web debugging proxy
‣ You can inspect, modify and record requests &
responses
‣ SSL Proxing
http://www.charlesproxy.com/documentation/faqs/ssl-connections-
from-within-iphone-applications/
‣ http://www.charlesproxy.com
‣ Price start from US$50

59. Charles Proxy

60. PonyDebugger

61. PonyDebugger
‣ Network Traffic Debugger
‣ Core Data Browser
‣ It is a client library and gateway server combination
that uses Chrome Developer Tools on your browser to
debug your application's network traffic and managed
object contexts.
‣ https://github.com/square/PonyDebugger

62. PonyDebugger

63. Deploymate

64. Deploymate
‣ If using an API introduced later than your target OS but
your app is targeting an older OS version, Xcode
doesn't warn you about it
‣ It helps identify unavailable, deprecated and obsolete
API
‣ http://www.deploymateapp.com/
‣ Price US$19.99

65. Deploymate

66. Spark Inspector

67. Spark Inspector
‣ Runtime Debugger for iOS
‣ Monitor & Experiment in Real-time
‣ See Notifications in Real-time
‣ http://sparkinspector.com/
‣ Price € 31,79

68. Spark Inspector

69. Demo

70. Remote

71. Remote debugging
‣ Apple Crash Reports
‣ PLCrashReporter
‣ TestFlight

72. Apple Crash Reports

73. Apple Crash Reports
‣ For app published on App Store, you can acquire crash
log from iTunes Connect and import it into Organizer
for symbolication
‣ To symbolicate a crash log, Xcode needs to have access
to the matching application binary that was uploaded
to the App Store, and the .dSYM file that was
generated when that binary was built. This must be an
exact match
‣ https://itunesconnect.apple.com

74. Apple Crash Reports

75. Apple Crash Reports

76. Xcode Symbolication

77. PLCrashReporter

78. PLCrashReporter
‣ In-process CrashReporter framework for the iPhone
and Mac OS X
‣ Handles both uncaught Objective-C exceptions and
fatal signals
‣ Backtraces for all active threads are provided
‣ https://code.google.com/p/plcrashreporter/

79. PLCrashReporter
- (void) handleCrashReport {
PLCrashReporter *crashReporter = [PLCrashReporter sharedReporter];
NSData *crashData;
NSError *error;
// Try loading the crash report
crashData = [crashReporter loadPendingCrashReportDataAndReturnError: &error];
if (crashData == nil) {
NSLog(@"Could not load crash report: %@", error);
goto finish;
}
PLCrashReport *report = [[[PLCrashReport alloc] initWithData: crashData error: &error] autorelease];
if (report == nil) {
NSLog(@"Could not parse crash report");
goto finish;
}
....
return;
}
// from UIApplicationDelegate protocol
- (void) applicationDidFinishLaunching: (UIApplication *) application {
PLCrashReporter *crashReporter = [PLCrashReporter sharedReporter];
NSError *error;
// Check if we previously crashed
if ([crashReporter hasPendingCrashReport])
[self handleCrashReport];
// Enable the Crash Reporter
if (![crashReporter enableCrashReporterAndReturnError: &error])
NSLog(@"Warning: Could not enable crash reporter: %@", error);
}

80. TestFlight

81. TestFlight
‣ Invite your testers, drop in the SDK and start uploading
your builds.
‣ Upload your builds and TestFlight takes care of the
rest. Painless over-the-air distribution to your testers
and distribution lists.
‣ Complete tracking of your build, from distribution to
sessions, checkpoints and crashes.
‣ https://testflightapp.com

82. TestFlight Apps Management

83. TestFlight Crashes

84. Resources

85. Resources
‣ Links
‣ Videos

86. Links

87. Links
‣ Overview of iOS Crash Reporting Tools
http://www.raywenderlich.com/33669/overview-of-ios-crash-
reporting-tools-part-1
http://www.raywenderlich.com/33669/overview-of-ios-crash-
reporting-tools-part-2
‣ How to use Instruments in Xcode
http://www.raywenderlich.com/23037/how-to-use-instruments-in-
xcode
‣ Demystifying iOS Application Crash Log
http://www.raywenderlich.com/23704/demystifying-ios-application-
crash-logs

88. Links
‣ Intermediate Debugging with Xcode 4.5
http://www.raywenderlich.com/28289/debugging-ios-apps-in-
xcode-4-5
‣ Xcode LLDB Tutorial
http://www.cimgf.com/2012/12/13/xcode-lldb-tutorial/
‣ iOS Simulator Tips & Tricks
http://mobile.tutsplus.com/tutorials/iphone/ios-simulator/

89. Links
‣ Compiler Warnings for Objective-C Developers
http://oleb.net/blog/2013/04/compiler-warnings-for-objective-c-
developers/
‣ Defensive Programming in Cocoa
http://www.mikeash.com/pyblog/friday-qa-2010-08-27-defensive-
programming-in-cocoa.html
‣ Testing and Debugging in iOS Simulator
https://developer.apple.com/library/ios/#documentation/IDEs/
Conceptual/iOS_Simulator_Guide/TestingontheiOSSimulator/
TestingontheiOSSimulator.html

90. Links
‣ iOS Debugging (slide by Dave Kozol)
http://arbormoon.com/sites/default/files/
ASIDebuggingCocoaConfChicago.pdf
‣ Strong, Better, Faster with Instruments and Debugging
(slide by Kyle Richter)
http://dragonforged.com/CocoaConf.pdf
‣ LLDB Script Examples
http://llvm.org/svn/llvm-project/lldb/trunk/examples/

91. Videos

92. Videos
‣ WWDC 2012 - 415 - Debugging with LLDB
‣ WWDC 2011 - 321 - Migrating from GDB to LLDB
‣ WWDC 2010 - 316 - Debugging with Xcode 4 and LLDB
‣ NSScreenCast - 002 - Memory Problems

93. Final Thoughts

94. Final Thoughts
‣ Don’t use NSLog anymore ;)
‣ Create your Xcode Behaviors
‣ Breakpoints are your friends
‣ LLDB is a promising youngster
‣ Tools can save your life
‣ The QA phase is essential

95. Thank you
Massimo Oliviero
massimo.oliviero@gmail.com
http://www.massimooliviero.net
follow me on twitter @maxoly
http://www.slideshare.net/MassimoOliviero
https://speakerdeck.com/massimooliviero