关于LLDB调试，不少iOS开发者可能就是停留在会下简单的断点，使用最多命令也就是po。无可厚非，这些简单的调试对于简单的问题来讲应该是游刃有余。可是若是稍微复杂一些的问题，好比我以前遇到过友盟SDK里面的一个问题。我很想往里面下一个断点，但是对于的静态库来讲，这根本不可能，最终仍是咱们组大牛使用命令的方式下了断点解决了这个问题。感受这些知识颇有必要，我因而把LLDB的基本调试命令都学习了一下，并在此与你们分享。.a
虽然博客很长，不过耐心看完，而后动手实践，必定会有很大帮助。html
breakpoint
给某个文件的某一行下断点。可使用以下两种方法，好比我想给Foo.m文件的26行下一个断点。可使用以下的方法。git
(lldb) breakpoint set --file Foo.m --line 26
若是出现以下提示则说明设置断点成功github
Breakpoint 2: where = BreakPointDemo`-[Foo foo] + 23 at Foo.m:26, address = 0x000000010b22e687
也可使用简写的形式以下。objective-c
(lldb) breakpoint set -f Foo.m -l 26
固然咱们也能够直接给某个函数下断点,可使用下面两种方法shell
(lldb) breakpoint set --name foo (lldb) breakpoint set -n foo
固然咱们也能够在一次命令中为下多个函数下断点express
(lldb) breakpoint set --name foo --name bar
咱们也能够更明确的指定是方法，若是是C的方法，可使用以下两种的方法打断点，第二种方法M须要大写数组
(lldb) breakpoint set --method cplusFoo (lldb) breakpoint set -M cplusFoo
若是是OC的方法，可使用如下两种方式打断点，第二种S须要大写架构
(lldb) breakpoint set --selector foo (lldb) breakpoint set -S foo
若是是C语言，仍是只能使用上面介绍的--name的方式，不能直接指定对应的方法app
固然，还有一个必杀器，就是使用正则,匹配你要打断点的函数。这个不限语言less
(lldb) breakpoint set -r cFoo (lldb) breakpoint set -r foo
也能够指定加载的动态库
(lldb) breakpoint set --shlib foo.dylib --name foo (lldb) breakpoint set -s foo.dylib -n foo
咱们一样能够对命令进行简写。下面两个命令的效果是同样的
(lldb) breakpoint set -n "-[Foo foo]" (lldb) br s -n "-[Foo foo]"
想要查看有多少断点可使用
(lldb) breakpoint list
打印的结果以下
Current breakpoints: 1: file = '/Users/jianquan/Xcode/BreakPointDemo/BreakPointDemo/ViewController.m', line = 20, exact_match = 0, locations = 0 (pending) 2: file = '/Users/jianquan/Xcode/BreakPointDemo/BreakPointDemo/ViewController.mm', line = 33, exact_match = 0, locations = 1, resolved = 1, hit count = 0 2.1: where = BreakPointDemo`::-[ViewController viewDidLoad]() + 186 at ViewController.mm:34, address = 0x0000000105f8362a, resolved, hit count = 0 ......
咱们能够对断点进行相关的操做，好比在执行到2.1断点的时候打印追踪轨迹。bt是
(lldb) breakpoint command add 2.1 Enter your debugger command(s). Type 'DONE' to end. > bt > DONE
除了add，还要delete等命令，这些命令不须要死记硬背，可使用help命令。
(lldb) help break command
add -- Add LLDB commands to a breakpoint, to be executed whenever the
breakpoint is hit. If no breakpoint is specified, adds the
commands to the last created breakpoint.
delete -- Delete the set of commands from a breakpoint.
list -- List the script or set of commands to be executed when the
breakpoint is hit.
要查看更详细的命令用途,使用help <command> <subcommand>.好比查看add命令用法
(lldb) help break command add ...... Enter your Python command(s). Type 'DONE' to end. > def breakpoint_output (bp_no): > out_string = "Hit breakpoint number " + repr (bp_no) > print out_string > return True > breakpoint_output (1) > DONE
能够看到其实这里面的命令大部分是Python脚本，不熟悉Python，暂时尚未仔细研究。
补充一点使用了以后如何删除断点呢,命令说明以下。
breakpoint delete [-Df] [<breakpt-id | breakpt-id-list>]
我如今用breakpoint list查个人进程
Current breakpoints: 1: file = '/Users/jianquan/Xcode/BreakPointDemo/BreakPointDemo/ViewController.m', line = 20, exact_match = 0, locations = 0 (pending) 2: file = '/Users/jianquan/Xcode/BreakPointDemo/BreakPointDemo/ViewController.mm', line = 29, exact_match = 0, locations = 1, resolved = 1, hit count = 1 2.1: where = BreakPointDemo`::-[ViewController viewDidLoad]() + 105 at ViewController.mm:30, address = 0x00000001025b55c9, resolved, hit count = 1 4: name = 'foo', locations = 1, resolved = 1, hit count = 0 4.1: where = BreakPointDemo`-[Foo foo] + 23 at Foo.m:26, address = 0x00000001025b5517, resolved, hit count = 0 5: regex = 'cFoo', locations = 2, resolved = 2, hit count = 0 5.1: where = BreakPointDemo`cFoo + 15 at CFoo.c:13, address = 0x00000001025b591f, resolved, hit count = 0 5.2: where = libicucore.A.dylib`icu::MeasureUnit::createCubicFoot(UErrorCode&), address = 0x00000001051b808a, resolved, hit count = 0
若果我要删除5.1断点我就使用breakpoint delete 5.1，若是我要删除5下面的全部断点，使用breakpoint delete 5,这样5.1和5.2都会删除。
删除全部的断点使用
(lldb) breakpoint delete About to delete all breakpoints, do you want to do that?: [Y/n] y All breakpoints removed. (4 breakpoints)
watchpoint
这个主要是用于观察变量值的具体变化
好比我须要观察某个变量a的值变化,我可使用以下命令
(lldb) watchpoint set variable a
成功添加watchpoint后结果以下。
Watchpoint created: Watchpoint 1: addr = 0x7fff5913ca3c size = 4 state = enabled type = w
declare @ '/Users/jianquan/Xcode/BreakPointDemo/BreakPointDemo/ViewController.mm:25'
watchpoint spec = 'a'
new value: 10
也能够在这里添加.
而后咱们能够设置在a的值变化为某个特定值以后触。
(lldb) watchpoint modify -c '(a=100)'
咱们这个时候能够看一下具体断点的参数，使用watchpoint list命令
(lldb) watchpoint list
Number of supported hardware watchpoints: 4
Current watchpoints:
Watchpoint 1: addr = 0x7fff4fcb7a3c size = 4 state = enabled type = w
declare @ '/Users/jianquan/Xcode/BreakPointDemo/BreakPointDemo/ViewController.mm:25'
watchpoint spec = 'a'
new value: 10
condition = '(a=100)'
能够看到咱们观察的变量的地址，声明变量的代码在第几行，已经具体的变量名是a,当前的值是10，触发的条件是'(a=100)'
而后咱们执行以下命令，就能够看到断点到a的值变为100的地方
(lldb) c Process 16596 resuming 2017-02-09 11:12:14.693 BreakPointDemo[16596:6050498] foo is foo 2017-02-09 11:12:14.693 BreakPointDemo[16596:6050498] bar is bar Watchpoint 1 hit: old value: 10 new value: 100
能够看到这个地方a的值已经发生改变。咱们能够再使用watchpoint list命令看看具体值的变化
(lldb) watchpoint list
Number of supported hardware watchpoints: 4
Current watchpoints:
Watchpoint 1: addr = 0x7fff4fcb7a3c size = 4 state = enabled type = w
declare @ '/Users/jianquan/Xcode/BreakPointDemo/BreakPointDemo/ViewController.mm:25'
watchpoint spec = 'a'
old value: 10
new value: 100
condition = '(a=100)'
固然，还有一个特别好用的命令就是bt命令咱们能够用它来追踪程序运行的过程。
(lldb) bt
* thread #1: tid = 0x5c52c2, 0x000000010ff465fe BreakPointDemo`::-[ViewController viewDidLoad](self=0x00007f932cc07c50, _cmd="viewDidLoad") + 158 at ViewController.mm:36, queue = 'com.apple.main-thread', stop reason = watchpoint 1
* frame #0: 0x000000010ff465fe BreakPointDemo`::-[ViewController viewDidLoad](self=0x00007f932cc07c50, _cmd="viewDidLoad") + 158 at ViewController.mm:36
frame #1: 0x000000011112ba3d UIKit`-[UIViewController loadViewIfRequired] + 1258
......
咱们可使用frame命令查看变量a的具体值。
(lldb) frame variable a (int) a = 100
最后补充一点watchpoint list的东西。这个命令包括了三个可选参数，咱们可使用help命令查看具体的值
(lldb) help watchpoint list
-b ( --brief )
Give a brief description of the watchpoint (no location info).
-f ( --full )
Give a full description of the watchpoint and its locations.
-v ( --verbose )
Explain everything we know about the watchpoint (for debugging
debugger bugs).
-b是比较简略的信息，-f是比较全面的信息，-v是完整的信息。通过个人实验，若是使用watchpoint list,默认的是 watchpoint list -f。
process
使用process命令也能够作不少有趣的操做。具体能作什么，咱们也可以使用help命令查看
(lldb) process help
attach -- Attach to a process.
connect -- Connect to a remote debug service.
continue -- Continue execution of all threads in the current process.
detach -- Detach from the current target process.
handle -- Manage LLDB handling of OS signals for the current target
......
查看更详细的命令使用help <command> <subcommand>。好比
(lldb) help process attach
这些命令在我目前平常开发中其实不怎么使用，可能我功力还不足吧。
thread
其实这个功能主要就是断点调试里面的以下这个功能。
咱们可使用thread命令来作一些断点的操做，具体有那些命令咱们可使用thread help进行查看。
(lldb) thread help
......
select -- Change the currently selected thread.
step-in -- Source level single step, stepping into calls.
Defaults to current thread unless specified.
step-inst -- Instruction level single step, stepping into calls.
Defaults to current thread unless specified.
step-inst-over -- Instruction level single step, stepping over calls.
Defaults to current thread unless specified.
step-out -- Finish executing the current stack frame and stop after
returning. Defaults to current thread unless
specified.
step-over -- Source level single step, stepping over calls.
Defaults to current thread unless specified.
step-scripted -- Step as instructed by the script class passed in the -C
option.
until -- Continue until a line number or address is reached by
the current or specified thread. Stops when returning
from the current function as a safety measure.
用得比较多的应该是 step-开头的这几个命令，使用起来很容易。我我的感受比用鼠标点击断点好用多了~
EXAMINING THREAD STATE
这个使用的也主要仍是thread命令，主要是使用如下几个命令。
检查当前进程的状态，可使用以下命令。
lldb) thread list Process 22323 stopped * thread #1: tid = 0x62d0d7, 0x00000001082185fe BreakPointDemo`::-[ViewController viewDidLoad](self=0x00007ff81b60ab20, _cmd="viewDidLoad") + 158 at ViewController.mm:36, queue = 'com.apple.main-thread', stop reason = step until ......
*代表的就是当前的线程，可使用以下的命令获得线程的回溯，这个词我也不肯定怎么表达好，backtrace，也能够说是追踪。
lldb) thread backtrace
* thread #1: tid = 0x62d0d7, 0x00000001082185fe BreakPointDemo`::-[ViewController viewDidLoad](self=0x00007ff81b60ab20, _cmd="viewDidLoad") + 158 at ViewController.mm:36, queue = 'com.apple.main-thread', stop reason = step until
* frame #0: 0x00000001082185fe BreakPointDemo`::-[ViewController viewDidLoad](self=0x00007ff81b60ab20, _cmd="viewDidLoad") + 158 at ViewController.mm:36
frame #1: 0x00000001093fda3d UIKit`-[UIViewController loadViewIfRequired] + 1258
frame #2: 0x00000001093fde70 UIKit`-[UIViewController view] + 27
frame #3: 0x00000001092c74b5 UIKit`-[UIWindow addRootViewControllerViewIfPossible] + 71
frame #4: 0x00000001092c7c06 UIKit`-[UIWindow _setHidden:forced:] + 293
frame #5: 0x00000001092db519 UIKit`-[UIWindow makeKeyAndVisible] + 42
frame #6: 0x0000000109253f8d UIKit`-[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 4818
frame #7: 0x000000010925a0ed UIKit`-[UIApplication _runWithMainScene:transitionContext:completion:] + 1731
frame #8: 0x000000010925726d UIKit`-[UIApplication workspaceDidEndTransaction:] + 188
frame #9: 0x000000010c3886cb FrontBoardServices`__FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 24
frame #10: 0x000000010c388544 FrontBoardServices`-[FBSSerialQueue _performNext] + 189
frame #11: 0x000000010c3888cd FrontBoardServices`-[FBSSerialQueue _performNextFromRunLoopSource] + 45
frame #12: 0x0000000108ddc761 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
frame #13: 0x0000000108dc198c CoreFoundation`__CFRunLoopDoSources0 + 556
frame #14: 0x0000000108dc0e76 CoreFoundation`__CFRunLoopRun + 918
frame #15: 0x0000000108dc0884 CoreFoundation`CFRunLoopRunSpecific + 420
frame #16: 0x0000000109255aea UIKit`-[UIApplication _run] + 434
frame #17: 0x000000010925bc68 UIKit`UIApplicationMain + 159
frame #18: 0x000000010821899f BreakPointDemo`main(argc=1, argv=0x00007fff579e7600) + 111 at main.m:14
frame #19: 0x000000010bbee68d libdyld.dylib`start + 1
固然咱们若是想看全部线程的backtrace，可使用thread backtrace all命令。内容太多，我这里就不演示log输出了。
若是咱们想单独查看某个线程，咱们能够先使用thread select 2跳到某个具体的线程，而后再进行其余操做，好比thread backtrace
EXAMINING STACK FRAME STATE
为了方便的观测架构参数和本地变量，咱们可使用 frame variable 命令
若是我什么参数也不加，将会把全部的参数和本地变量到打印出来。
(lldb) frame variable (ViewController *) self = 0x00007ff81b60ab20 (SEL) _cmd = "viewDidLoad" (int) a = 100 (Foo *) foo = 0x000061800000e820 (BreakPointDemoNameSpace::BreakPointClass *) cplusFoo = 0x3ff0000000000000
要打印某个变量须要在参数里面指定，这个命令咱们在前面也使用过,好比要查看self
(lldb) frame variable self (ViewController *) self = 0x00007ff81b60ab20
更进一步，咱们能够查看一些子元素
(lldb) frame variable self->isa (Class) self->isa = ViewController
命令虽然不是完整的表达式解释器，当时能够识别一些基本的操做 好比 &, *, ->, []，不是重载运算符，数组也可使用，由于数组自己也是指针。
(lldb) frame variable *self
(ViewController) *self = {
UIViewController = {
UIResponder = {
NSObject = {
isa = ViewController
}
......
}
和以前thread命令很相似，我可使用frame select去选择另外的一个frame
(lldb) frame select 9
若是想看更复杂的数据，咱们可使用expression命令
(lldb) expression self (ViewController *) $0 = 0x00007fefa4705110
更复杂一些，咱们能够用来输出一个表达式
(lldb) expr (int) printf ("I have a pointer 0x%llx.\n", self)
I have a pointer 0x7fefa4705110.
(int) $1 = 33
咱们能够继续以以前的命令来操做
(lldb) expr self = $0 (ViewController *) $2 = 0x00007fefa4705110
固然这个expr用途感受不大。
call
其实这个命令彻底可使用po进行替代，call通常能够用来调用不须要返回值的调试命令，好比更改View的背景颜色，如下两个命令均可以达到类似的做用，更改当前View的背景颜色值。
(lldb) po [self.view setBackgroundColor:[UIColor redColor]] (lldb) call [self.view setBackgroundColor:[UIColor redColor]]
image
虽然只是一个简单的命令，可是我仍是感受这是一个比较重要也比较实用的命令， 命令可用于寻址。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
//测试image命令使用
NSArray *arr=[[NSArray alloc] initWithObjects:@"1",@"2", nil];
NSLog(@"%@",arr[2]);
能够很明显的看到数组越界了，而后咱们运行程序，能够看到程序报以下错误
*** First throw call stack:
(
0 CoreFoundation 0x000000011039dd4b __exceptionPreprocess + 171
1 libobjc.A.dylib 0x000000010fd5421e objc_exception_throw + 48
2 CoreFoundation 0x00000001102d82bb -[__NSArrayI objectAtIndex:] + 155
3 BreakPointDemo 0x000000010f77d444 -[ViewController viewDidLoad] + 340
4 UIKit 0x0000000110963a3d -[UIViewController loadViewIfRequired] + 1258
5 UIKit 0x0000000110963e70 -[UIViewController view] + 27
6 UIKit 0x000000011082d4b5 -[UIWindow addRootViewControllerViewIfPossible] + 71
7 UIKit 0x000000011082dc06 -[UIWindow _setHidden:forced:] + 293
8 UIKit 0x0000000110841519 -[UIWindow makeKeyAndVisible] + 42
9 UIKit 0x00000001107b9f8d -[UIApplication _callInitializationDelegatesForMainScene:transitionContext:] + 4818
10 UIKit 0x00000001107c00ed -[UIApplication _runWithMainScene:transitionContext:completion:] + 1731
11 UIKit 0x00000001107bd26d -[UIApplication workspaceDidEndTransaction:] + 188
12 FrontBoardServices 0x00000001138ee6cb __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 24
13 FrontBoardServices 0x00000001138ee544 -[FBSSerialQueue _performNext] + 189
14 FrontBoardServices 0x00000001138ee8cd -[FBSSerialQueue _performNextFromRunLoopSource] + 45
15 CoreFoundation 0x0000000110342761 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
16 CoreFoundation 0x000000011032798c __CFRunLoopDoSources0 + 556
17 CoreFoundation 0x0000000110326e76 __CFRunLoopRun + 918
18 CoreFoundation 0x0000000110326884 CFRunLoopRunSpecific + 420
19 UIKit 0x00000001107bbaea -[UIApplication _run] + 434
20 UIKit 0x00000001107c1c68 UIApplicationMain + 159
21 BreakPointDemo 0x000000010f77d8ef main + 111
22 libdyld.dylib 0x000000011315468d start + 1
)
咱们大概能够猜想程序是崩溃在第三行log，也就是地址为0x0000000104147544的地方，怎么来呢，瞎猜的，哈哈。其实原理很简单，由于个人Demo名字叫BreakPointDemo。其余的名字很明显是系统的库。虽然log的21行也有BreakPointDemo,可是通过观察应该是main函数，不在考虑范围以内。
咱们使用image 的 lookup命令，能够很快的定位到具体的代码行。
(lldb) image lookup --address 0x000000010f77d444
Address: BreakPointDemo[0x000000010f77d444] (BreakPointDemo.__TEXT.__text + 644)
Summary: BreakPointDemo`::-[ViewController viewDidLoad]() + 340 at ViewController.mm:46
看看咱们的Xcode文件的代码。确实是46行
断点位置
固然还有不少的命令咱们能够探索，使用image help能够查看，这些命令我暂时没有接触过，后续工做或者学习中使用到了我会更新上来。
为命令设置别名
好比p是frame variable的别名，p view其实是frame variable view。除了系统自建的LLDB别名，你也能够自定义别名。好比下面这个命令。掌握了规律以后，任何的命令咱们均可以本身设置别名。
(lldb) command alias bfl breakpoint set -f %1 -l %2 (lldb) bfl Foo.m 12
若是想要撤销别名使用
(lldb) command unalias bfl
固然还有一些LLDB的具体命令，咱们能够在官网查看： The LLDB Debugger
总结
这么长的文章，看到这里真的不容易，不过我相信你应该有所收获了。另外个人博客长期欢迎评论留言，相互探讨，不足之处欢迎批准指正。