LLDB是個開源的內置於XCode的調試工具，這里來理一理常用用法。
lldb對於命令的簡稱，是頭部匹配方式，只要不混淆，你可以隨意簡稱某個命令。結果為在xcode下驗證所得，可能與其它平台有所誤差。
1 打印值、修改值、調用方法
1.1 p、po 打印值
打印相關的命令有：p、po。
p 和 po 的區別在於使用 po 只會輸出對應的值，而 p 則會返回值的類型以及命令結果的引用名。
(lldb) p width
(CGFloat) $10 = 70
(lldb) po width
70
(lldb) p endTime
(__NSCFString *) $14 = 0x0000608000437660 @"08-11 11:43"
(lldb) po endTime
08-11 11:43對比結果:
po：輸出值
p：輸出值+值類型+引用名+內存地址(xcode中有內存地址，其它平台不確定)
除此之外，p還隱藏了一個有意思的功能，常量的進制轉換:
//默認打印為10進制
(lldb) p 100
(int) $8 = 100
//轉16進制
(lldb) p/x 100
(int) $9 = 0x00000064
//轉8進制
(lldb) p/o 100
(int) $10 = 0144
//轉二進制
(lldb) p/t 100
(int) $2 = 0b00000000000000000000000001100100
//字符轉10進制數字
(lldb) p/d 'A'
(char) $7 = 65
//10進制數字轉字符
(lldb) p/c 66
(int) $10 = B\0\0\01.2 expression 修改參數值
感覺exp命令是調試過程中最有價值有命令了，它可以打印值、修改值。
//expression打印值
(lldb) expression width
(CGFloat) $5 = 67
//expression修改值
(lldb) expression width = 80
(CGFloat) $6 = 80
//打印修改后結果
(lldb) p width
(CGFloat) $7 = 80
(lldb)expression：同樣可以輸出值+值類型+引用名，但其一般用於修改。
1.3 call 方法調用
在斷點調用某個方法，並輸出此方法的返回值。
(lldb) call width
(CGFloat) $12 = 70
(lldb) call endTime
(__NSCFString *) $16 = 0x0000608000437660 @"08-11 11:43"call：同樣為輸出值+值類型+引用名
2 Thread
2.1 堆棧打印 thread backtrace
如果嫌堆棧打印太長，可以加一個值限制，如bt 10，只打印
(lldb) bt 10
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
* frame #0: 0x00000001005e4906 DiDi`-[FW_HomeCell_HotBill setDataSource:](self=0x00007fd3938a7800, _cmd="setDataSource:", dataSource=0x00006080001c8bb0) at FW_HomeCell.m:357
frame #1: 0x00000001009a9fd7 DiDi`-[FW_MyHomeTableView tableView:cellForRowAtIndexPath:](self=0x00007fd3921fec00, _cmd="tableView:cellForRowAtIndexPath:", tableView=0x00007fd3921fec00, indexPath=0xc000000000000316) at FW_MyHomeTableView.m:247
frame #2: 0x00000001055a2ab2 UIKit`-[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] + 750
frame #3: 0x00000001055a2cf8 UIKit`-[UITableView _createPreparedCellForGlobalRow:willDisplay:] + 74
frame #4: 0x0000000105577639 UIKit`-[UITableView _updateVisibleCellsNow:isRecursive:] + 2845
frame #5: 0x00000001055abccc UIKit`-[UITableView _performWithCachedTraitCollection:] + 111
frame #6: 0x0000000105592e7a UIKit`-[UITableView layoutSubviews] + 233
frame #7: 0x00000001054f955b UIKit`-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1268
frame #8: 0x0000000105114904 QuartzCore`-[CALayer layoutSublayers] + 146
frame #9: 0x0000000105108526 QuartzCore`CA::Layer::layout_if_needed(CA::Transaction*) + 3702.2 thread return 跳出當前方法的執行
Debug的時候，也許會因為各種原因，我們不想讓代碼執行某個方法，或者要直接返回一個想要的值。這時候就該thread return上場了。
有返回值的方法里，如：numberOfSectionsInTableView:，直接thread return 10，就可以直接跳過方法執行，返回10.
//跳出方法
(lldb) thread return
//讓帶有返回int值的方法直接跳出，並返回值10
(lldb) thread return 102.3 流程控制
實際上使用xcode自帶的可視化工具來控制“繼續”“暫停”“下一步”“進入”“跳出”更簡單
繼續：continue, c
下一步：next, n
進入：step, s
跳出：finish, f2.4 跳幀 frame select N
2.1中打印有10幀，如果我想跳轉到第1幀：frame select 1
(lldb) frame select 1
frame #1: 0x0000000105e91c3c DiDi`-[FW_HomeViewController tableView:cellForRowAtIndexPath:](self=0x00007fbf9f73b410, _cmd="tableView:cellForRowAtIndexPath:", tableView=0x00007fbfa11dc400, indexPath=0xc000000000a00316) at FW_HomeViewController.m:597
594 break;
595
596 case 3: {
-> 597 cell.[4md[0mataSource = _hotBills[indexPath.row];
598 cell.textSelect = ^(UITextField *text) {
599 weakSelf.curruntText = text;
600 };2.5 查看幀變量 frame variable
(lldb) frame variable
(FW_HomeViewController *) self = 0x00007faccbf587d0
(SEL) _cmd = "tableView:cellForRowAtIndexPath:"
(UITableView *) tableView = 0x00007faccd09b400
(NSIndexPath *) indexPath = 0xc000000000000316
(FW_HomeViewController *) weakSelf = 0x00007faccbf587d0
(FW_HomeCell_HotBill *) cell = 0x00007faccc101a00
(UIView *) model = 0x00007fff52c13d90
(FW_HomeCell_HotBill *) billCell = 0x00000001124e99f63 Image
3.1 image lookup -address 查找崩潰位置
當你遇見數組崩潰，你又沒有找到崩潰的位置，只扔給你一堆報錯信息，這時候image lookup來幫助你。如下
0 CoreFoundation 0x0000000103209b0b __exceptionPreprocess + 171
1 libobjc.A.dylib 0x00000001079db141 objc_exception_throw + 48
2 CoreFoundation 0x000000010313effb -[__NSArrayM objectAtIndex:] + 203
3 DiDi 0x00000001009a9f3a -[FW_MyHomeTableView tableView:cellForRowAtIndexPath:] + 1322
4 UIKit 0x00000001055a2ab2 -[UITableView _createPreparedCellForGlobalRow:withIndexPath:willDisplay:] + 750
5 UIKit 0x00000001055a2cf8 -[UITableView _createPreparedCellForGlobalRow:willDisplay:] + 74
6 UIKit 0x0000000105577639 -[UITableView _updateVisibleCellsNow:isRecursive:] + 2845
7 UIKit 0x00000001055abccc -[UITableView _performWithCachedTraitCollection:] + 111
8 UIKit 0x0000000105592e7a -[UITableView layoutSubviews] + 233
9 UIKit 0x00000001054f955b -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1268
10 QuartzCore 0x0000000105114904 -[CALayer layoutSublayers] + 146尋找自己項目的標識，看到frame3位置，你只需這樣查找位置：
image lookup -a 0x00000001009a9f3a
Address: DiDi[0x0000000100609f3a] (DiDi.__TEXT.__text + 6323194)
Summary: DiDi`-[FW_MyHomeTableView tableView:cellForRowAtIndexPath:] + 1322 at FW_MyHomeTableView.m:243項目中FW_MyHomeTableView.m:243，perfect!
3.2 image lookup -name 查找方法來源
此命令可以用來查找方法的來源。包括在第三方SDK中的方法，也能被查到。
例：查找transformOtherModelToSuit:
(lldb) image lookup -n transformOtherModelToSuit:
1 match found in /Users/xxx/Library/Developer/Xcode/DerivedData/DiDi-cwpbvvyvqmeijmcjnneothzuthsy/Build/Products/Debug-iphonesimulator/DiDi.app/DiDi:
Address: DiDi[0x0000000100293d60] (DiDi.__TEXT.__text + 2693664)
Summary: DiDi`+[FW_BetFunction transformOtherModelToSuit:] at FW_BetFunction.m:1073.3 image lookup –type 查看成員
查看某個class的所有屬性和成員變量。不過貌似frameWork庫中文件不能查看。
(lldb) image lookup -t MatchEvent
1 match found in /Users/xxxx/Library/Developer/Xcode/DerivedData/DiDi-cwpbvvyvqmeijmcjnneothzuthsy/Build/Products/Debug-iphonesimulator/DiDi.app/DiDi:
id = {0x00433d32}, name = "MatchEvent", byte-size = 48, decl = MatchEvent.h:11, compiler_type = "@interface MatchEvent : NSObject{
BOOL _isHome;
NSString * _playerName;
NSString * _timePoint;
NSString * _eventType;
NSString * _eventDesc;
}
@property ( getter = isHome,setter = setIsHome:,assign,readwrite,nonatomic ) BOOL isHome;
@property ( getter = playerName,setter = setPlayerName:,readwrite,copy,nonatomic ) NSString * playerName;
@property ( getter = timePoint,setter = setTimePoint:,readwrite,copy,nonatomic ) NSString * timePoint;
@property ( getter = eventType,setter = setEventType:,readwrite,copy,nonatomic ) NSString * eventType;
@property ( getter = eventDesc,setter = setEventDesc:,readwrite,copy,nonatomic ) NSString * eventDesc;
@end"4 breakpoint
4.1 文件名+行號 breakpoint set -f xxx -l xxx
我們平時操作xcode，在某一行點下斷點，其實操作的就是這個命令。
(lldb) breakpoint set -f FW_ProfilesDetailModel.m -l 95
Breakpoint 3: where = DiDi`-[FW_ProfilesDetailModel incomeRate] + 27 at FW_ProfilesDetailModel.m:96, address = 0x0000000105b404bb4.2 函數名斷點
4.2.1 方法名斷點 breakpoint set -n 方法名
(lldb) breakpoint set -n viewDidLoad
Breakpoint 4: 414 locations.Tips:這里要說一下，xcode其實也有函數名斷點，不過用breakpoint set -n實現，比xcode下斷點快N倍，不過xcode下的斷點還給提示所有斷到的位置。
4.2.2 類中方法斷點 breakpoint set -n “-[類名 方法名]”
(lldb) breakpoint set -n "-[FW_MyHomeViewController viewDidLoad]"
Breakpoint 8: where = DiDi`-[FW_MyHomeViewController viewDidLoad] + 20 at FW_MyHomeViewController.m:58, address = 0x0000000105aec944注意：-[FW_MyHomeViewController viewDidLoad]，外面一定要加雙引
號，不然會誤識別為-[FW_MyHomeViewController`
4.3 條件斷點 breakpoint set -c “xxxx”
和xcode中symbolic Breakpoint功能相同，我在FW_HomeCell.m 362行下斷點，但又想過濾僅width>68的狀態，操作如下：
breakpoint set -f FW_HomeCell.m -l 362 -c "width > 68"
Breakpoint 5: where = DiDi`-[FW_HomeCell_HotBill setDataSource:] + 2006 at FW_HomeCell.m:363, address = 0x000000010d22e0a64.4 查看斷點列表 breakpoint list
(lldb) breakpoint list
Current breakpoints:
8: name = '-[FW_MyHomeViewController viewDidLoad]', locations = 1, resolved = 1, hit count = 2
8.1: where = DiDi`-[FW_MyHomeViewController viewDidLoad] + 20 at FW_MyHomeViewController.m:58, address = 0x0000000105aec944, resolved, hit count = 2
9: file = '/Users/xxxx/didi-ios/DiDi/FollowWinner/Model/FW_HomeModel.m', line = 24, exact_match = 0, locations = 1, resolved = 1, hit count = 0
9.1: where = DiDi`+[FW_HomeModel_Rank parasWithDict:limitNickLength:] + 89 at FW_HomeModel.m:24, address = 0x00000001061bc169, resolved, hit count = 04.5 禁用/啟用斷點 breakpoint disable/enable
//禁用斷點
(lldb) breakpoint disable 9
1 breakpoints disabled.
(lldb) breakpoint list
Current breakpoints:
9: file = '/Users/zmz/didi-ios/DiDi/FollowWinner/Model/FW_HomeModel.m', line = 24, exact_match = 0, locations = 1 Options: disabled
9.1: where = DiDi`+[FW_HomeModel_Rank parasWithDict:limitNickLength:] + 89 at FW_HomeModel.m:24, address = 0x00000001061bc169, unresolved, hit count = 0
//啟用斷點
(lldb) breakpoint enable 9
1 breakpoints enabled.
(lldb) breakpoint list
Current breakpoints:
9: file = '/Users/zmz/didi-ios/DiDi/FollowWinner/Model/FW_HomeModel.m', line = 24, exact_match = 0, locations = 1, resolved = 1, hit count = 0
9.1: where = DiDi`+[FW_HomeModel_Rank parasWithDict:limitNickLength:] + 89 at FW_HomeModel.m:24, address = 0x00000001061bc169, resolved, hit count = 04.6 移除斷點 breakpoint delete
(lldb) breakpoint delete 8
1 breakpoints deleted; 0 breakpoint locations disabled.
(lldb) breakpoint list
Current breakpoints:
9: file = '/Users/xxxx/didi-ios/DiDi/FollowWinner/Model/FW_HomeModel.m', line = 24, exact_match = 0, locations = 1, resolved = 1, hit count = 0
9.1: where = DiDi`+[FW_HomeModel_Rank parasWithDict:limitNickLength:] + 89 at FW_HomeModel.m:24, address = 0x00000001061bc169, resolved, hit count = 0結語：
有了這些命令，調試起來肯定就得心應手了。總結下常用的，供多看幾遍加深回憶：
堆棧相關：bt查看堆棧、frame select跳幀、frame variable查看幀參數、thread return跳出當前執行、【step/finish/next/continue】進入/跳出/下一步/跳出本斷點
斷點相關：breakpoint set -f -l -c條件斷點、breakpoint set -n方法斷點、breakpoint delete斷點移除、breakpoint list斷點列表
image命令：image lookup -address崩潰定位、image lookup -name方法來源、 image lookup –type 查看成員
LLDB支持簡寫