iOS调试，找出错误代码所在位置

转帖 http://www.starfelix.com/blog/2014/03/17/lldbdiao-shi-ming-ling-chu-tan/

其中的一部分

image 命令可用于寻址，有多个组合命令。比较实用的用法是用于寻找栈地址对应的代码位置。 下面我写了一段代码

NSArray *arr=[[NSArray alloc] initWithObjects:@"1",@"2", nil];
NSLog(@"%@",arr[2]);

这段代码有明显的错误，程序运行这段代码后会抛出下面的异常：

*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayI objectAtIndex:]: index 2 beyond bounds [0 .. 1]'
*** First throw call stack:
(
  0   CoreFoundation                      0x0000000101951495 __exceptionPreprocess + 165
  1   libobjc.A.dylib                     0x00000001016b099e objc_exception_throw + 43
  2   CoreFoundation                      0x0000000101909e3f -[__NSArrayI objectAtIndex:] + 175
  3   ControlStyleDemo                    0x0000000100004af8 -[RootViewController viewDidLoad] + 312
  4   UIKit                               0x000000010035359e -[UIViewController loadViewIfRequired] + 562
  5   UIKit                               0x0000000100353777 -[UIViewController view] + 29
  6   UIKit                               0x000000010029396b -[UIWindow addRootViewControllerViewIfPossible] + 58
  7   UIKit                               0x0000000100293c70 -[UIWindow _setHidden:forced:] + 282
  8   UIKit                               0x000000010029cffa -[UIWindow makeKeyAndVisible] + 51
  9   ControlStyleDemo                    0x00000001000045e0 -[AppDelegate application:didFinishLaunchingWithOptions:] + 672
  10  UIKit                               0x00000001002583d9 -[UIApplication _handleDelegateCallbacksWithOptions:isSuspended:restoreState:] + 264
  11  UIKit                               0x0000000100258be1 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1605
  12  UIKit                               0x000000010025ca0c -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 660
  13  UIKit                               0x000000010026dd4c -[UIApplication handleEvent:withNewEvent:] + 3189
  14  UIKit                               0x000000010026e216 -[UIApplication sendEvent:] + 79
  15  UIKit                               0x000000010025e086 _UIApplicationHandleEvent + 578
  16  GraphicsServices                    0x0000000103aca71a _PurpleEventCallback + 762
  17  GraphicsServices                    0x0000000103aca1e1 PurpleEventCallback + 35
  18  CoreFoundation                      0x00000001018d3679 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 41
  19  CoreFoundation                      0x00000001018d344e __CFRunLoopDoSource1 + 478
  20  CoreFoundation                      0x00000001018fc903 __CFRunLoopRun + 1939
  21  CoreFoundation                      0x00000001018fbd83 CFRunLoopRunSpecific + 467
  22  UIKit                               0x000000010025c2e1 -[UIApplication _run] + 609
  23  UIKit                               0x000000010025de33 UIApplicationMain + 1010
  24  ControlStyleDemo                    0x0000000100006b73 main + 115
  25  libdyld.dylib                       0x0000000101fe95fd start + 1
  26  ???                                 0x0000000000000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException

现在，我们怀疑出错的地址是0x0000000100004af8（可以根据执行文件名判断，或者最小的栈地址）。为了进一步精确定位，我们可以输入以下的命令：

image lookup --address 0x0000000100004af8
// 缩写
// im loo -a  0x0000000100004af8

命令执行后返回：

Address: ControlStyleDemo[0x0000000100004af8] (ControlStyleDemo.__TEXT.__text + 13288)
Summary: ControlStyleDemo`-[RootViewController viewDidLoad] + 312 at RootViewController.m:53

我们可以看到，出错的位置是RootViewController.m的第53行。