關於LLDB調試，不少iOS開發者可能就是停留在會下簡單的斷點，使用最多命令也就是po。無可厚非，這些簡單的調試對於簡單的問題來講應該是遊刃有餘。可是若是稍微複雜一些的問題，好比我以前遇到過友盟SDK裏面的一個問題。我很想往裏面下一個斷點，但是對於的靜態庫來講，這根本不可能，最終仍是咱們組大牛使用命令的方式下了斷點解決了這個問題。感受這些知識頗有必要，我因而把LLDB的基本調試命令都學習了一下，並在此與你們分享。.a
雖然博客很長，不過耐心看完，而後動手實踐，必定會有很大幫助。html
breakpoint
給某個文件的某一行下斷點。可使用以下兩種方法，好比我想給Foo.m文件的26行下一個斷點。可使用以下的方法。git
(lldb) breakpoint set --file Foo.m --line 26
若是出現以下提示則說明設置斷點成功github
Breakpoint 2: where = BreakPointDemo`-[Foo foo] + 23 at Foo.m:26, address = 0x000000010b22e687
也可使用簡寫的形式以下。objective-c
(lldb) breakpoint set -f Foo.m -l 26
固然咱們也能夠直接給某個函數下斷點,可使用下面兩種方法shell
(lldb) breakpoint set --name foo (lldb) breakpoint set -n foo
固然咱們也能夠在一次命令中爲下多個函數下斷點express
(lldb) breakpoint set --name foo --name bar
咱們也能夠更明確的指定是方法，若是是C的方法，可使用以下兩種的方法打斷點，第二種方法M須要大寫數組
(lldb) breakpoint set --method cplusFoo (lldb) breakpoint set -M cplusFoo
若是是OC的方法，可使用如下兩種方式打斷點，第二種S須要大寫架構
(lldb) breakpoint set --selector foo (lldb) breakpoint set -S foo
若是是C語言，仍是隻能使用上面介紹的--name的方式，不能直接指定對應的方法app
固然，還有一個必殺器，就是使用正則,匹配你要打斷點的函數。這個不限語言less
(lldb) breakpoint set -r cFoo (lldb) breakpoint set -r foo
也能夠指定加載的動態庫
(lldb) breakpoint set --shlib foo.dylib --name foo (lldb) breakpoint set -s foo.dylib -n foo
咱們一樣能夠對命令進行簡寫。下面兩個命令的效果是同樣的
(lldb) breakpoint set -n "-[Foo foo]" (lldb) br s -n "-[Foo foo]"
想要查看有多少斷點可使用
(lldb) breakpoint list
打印的結果以下
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 ......
咱們能夠對斷點進行相關的操做，好比在執行到2.1斷點的時候打印追蹤軌跡。bt是
(lldb) breakpoint command add 2.1 Enter your debugger command(s). Type 'DONE' to end. > bt > DONE
除了add，還要delete等命令，這些命令不須要死記硬背，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.
要查看更詳細的命令用途,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
能夠看到其實這裏面的命令大部分是Python腳本，不熟悉Python，暫時尚未仔細研究。
補充一點使用了以後如何刪除斷點呢,命令說明以下。
breakpoint delete [-Df] [<breakpt-id | breakpt-id-list>]
我如今用breakpoint list查個人進程
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
若果我要刪除5.1斷點我就使用breakpoint delete 5.1，若是我要刪除5下面的全部斷點，使用breakpoint delete 5,這樣5.1和5.2都會刪除。
刪除全部的斷點使用
(lldb) breakpoint delete About to delete all breakpoints, do you want to do that?: [Y/n] y All breakpoints removed. (4 breakpoints)
watchpoint
這個主要是用於觀察變量值的具體變化
好比我須要觀察某個變量a的值變化,我可使用以下命令
(lldb) watchpoint set variable a
成功添加watchpoint後結果以下。
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
也能夠在這裏添加.
而後咱們能夠設置在a的值變化爲某個特定值以後觸。
(lldb) watchpoint modify -c '(a=100)'
咱們這個時候能夠看一下具體斷點的參數，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)'
能夠看到咱們觀察的變量的地址，聲明變量的代碼在第幾行，已經具體的變量名是a,當前的值是10，觸發的條件是'(a=100)'
而後咱們執行以下命令，就能夠看到斷點到a的值變爲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
能夠看到這個地方a的值已經發生改變。咱們能夠再使用watchpoint list命令看看具體值的變化
(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，還有一個特別好用的命令就是bt命令咱們能夠用它來追蹤程序運行的過程。
(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
......
咱們可使用frame命令查看變量a的具體值。
(lldb) frame variable a (int) a = 100
最後補充一點watchpoint list的東西。這個命令包括了三個可選參數，咱們可使用help命令查看具體的值
(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是比較簡略的信息，-f是比較全面的信息，-v是完整的信息。通過個人實驗，若是使用watchpoint list,默認的是 watchpoint list -f。
process
使用process命令也能夠作不少有趣的操做。具體能作什麼，咱們也可以使用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
......
查看更詳細的命令使用help <command> <subcommand>。好比
(lldb) help process attach
這些命令在我目前平常開發中其實不怎麼使用，可能我功力還不足吧。
thread
其實這個功能主要就是斷點調試裏面的以下這個功能。
咱們可使用thread命令來作一些斷點的操做，具體有那些命令咱們可使用thread help進行查看。
(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.
用得比較多的應該是 step-開頭的這幾個命令，使用起來很容易。我我的感受比用鼠標點擊斷點好用多了~
EXAMINING THREAD STATE
這個使用的也主要仍是thread命令，主要是使用如下幾個命令。
檢查當前進程的狀態，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 ......
*代表的就是當前的線程，可使用以下的命令獲得線程的回溯，這個詞我也不肯定怎麼表達好，backtrace，也能夠說是追蹤。
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
固然咱們若是想看全部線程的backtrace，可使用thread backtrace all命令。內容太多，我這裏就不演示log輸出了。
若是咱們想單獨查看某個線程，咱們能夠先使用thread select 2跳到某個具體的線程，而後再進行其餘操做，好比thread backtrace
EXAMINING STACK FRAME STATE
爲了方便的觀測架構參數和本地變量，咱們可使用 frame variable 命令
若是我什麼參數也不加，將會把全部的參數和本地變量到打印出來。
(lldb) frame variable (ViewController *) self = 0x00007ff81b60ab20 (SEL) _cmd = "viewDidLoad" (int) a = 100 (Foo *) foo = 0x000061800000e820 (BreakPointDemoNameSpace::BreakPointClass *) cplusFoo = 0x3ff0000000000000
要打印某個變量須要在參數裏面指定，這個命令咱們在前面也使用過,好比要查看self
(lldb) frame variable self (ViewController *) self = 0x00007ff81b60ab20
更進一步，咱們能夠查看一些子元素
(lldb) frame variable self->isa (Class) self->isa = ViewController
命令雖然不是完整的表達式解釋器，當時能夠識別一些基本的操做 好比 &, *, ->, []，不是重載運算符，數組也可使用，由於數組自己也是指針。
(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去選擇另外的一個frame
(lldb) frame select 9
若是想看更復雜的數據，咱們可使用expression命令
(lldb) expression self (ViewController *) $0 = 0x00007fefa4705110
更復雜一些，咱們能夠用來輸出一個表達式
(lldb) expr (int) printf ("I have a pointer 0x%llx.\n", self)
I have a pointer 0x7fefa4705110.
(int) $1 = 33
咱們能夠繼續以以前的命令來操做
(lldb) expr self = $0 (ViewController *) $2 = 0x00007fefa4705110
固然這個expr用途感受不大。
call
其實這個命令徹底可使用po進行替代，call通常能夠用來調用不須要返回值的調試命令，好比更改View的背景顏色，如下兩個命令均可以達到類似的做用，更改當前View的背景顏色值。
(lldb) po [self.view setBackgroundColor:[UIColor redColor]] (lldb) call [self.view setBackgroundColor:[UIColor redColor]]
image
雖然只是一個簡單的命令，可是我仍是感受這是一個比較重要也比較實用的命令， 命令可用於尋址。比較實用的用法是用於尋找棧地址對應的代碼位置。 下面我寫了一段代碼
//測試image命令使用
NSArray *arr=[[NSArray alloc] initWithObjects:@"1",@"2", nil];
NSLog(@"%@",arr[2]);
能夠很明顯的看到數組越界了，而後咱們運行程序，能夠看到程序報以下錯誤
*** 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
)
咱們大概能夠猜想程序是崩潰在第三行log，也就是地址爲0x0000000104147544的地方，怎麼來呢，瞎猜的，哈哈。其實原理很簡單，由於個人Demo名字叫BreakPointDemo。其餘的名字很明顯是系統的庫。雖然log的21行也有BreakPointDemo,可是通過觀察應該是main函數，不在考慮範圍以內。
咱們使用image 的 lookup命令，能夠很快的定位到具體的代碼行。
(lldb) image lookup --address 0x000000010f77d444
Address: BreakPointDemo[0x000000010f77d444] (BreakPointDemo.__TEXT.__text + 644)
Summary: BreakPointDemo`::-[ViewController viewDidLoad]() + 340 at ViewController.mm:46
看看咱們的Xcode文件的代碼。確實是46行
斷點位置
固然還有不少的命令咱們能夠探索，使用image help能夠查看，這些命令我暫時沒有接觸過，後續工做或者學習中使用到了我會更新上來。
爲命令設置別名
好比p是frame variable的別名，p view其實是frame variable view。除了系統自建的LLDB別名，你也能夠自定義別名。好比下面這個命令。掌握了規律以後，任何的命令咱們均可以本身設置別名。
(lldb) command alias bfl breakpoint set -f %1 -l %2 (lldb) bfl Foo.m 12
若是想要撤銷別名使用
(lldb) command unalias bfl
固然還有一些LLDB的具體命令，咱們能夠在官網查看： The LLDB Debugger
總結
這麼長的文章，看到這裏真的不容易，不過我相信你應該有所收穫了。另外個人博客長期歡迎評論留言，相互探討，不足之處歡迎批准指正。