Swift 代码调试核武－LLDB调试基础

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http://blog.csdn.net/hello_hwc?viewmode=list
我的stackoverflow

前言：LLDB是个开源的调试器，与XCode绑定的

LLDB的使用中，Swift与Objective C还是有一些差别的

本文主要侧重LLDB的常用命令

资料（目前状态XCode 7.2 Swift 2.1.1），非XCode 7.2+本文代码可能不能运行

objc.io(强烈建议有Objective C经验，但是对LLDB不熟悉的深入研究下)
Apple官方文档
LLDB的文档
一个封装LLDB的库，可以辅助调试
2015 WWDC视频

对了，Swift到现在也不过一岁半，所以LLDB对于Swift的支持肯定不如OC那么好。

如何打开LLDB如何使用？

通常的方式就是断点，另外，关于利用XCode图形化调试，在我这篇文章里有详细讲解

本文适合XCode 7.2 ＋
不管是在程序中加断点

还是手动的暂停程序

让代码停在Swift Error 或者Objective C异常

停在Objective C异常

(lldb) br s -E  objc
Breakpoint 6: where = libobjc.A.dylib`objc_exception_throw,address = 0x000000010dededbb

停在Swift Error

(lldb) br s -E swift
Breakpoint 7: where = libswiftCore.dylib`swift_willThrow,address = 0x000000010e55ccc0

停在某一种类型的Swift Error

(lldb) br s -E swift -O EnumError
Breakpoint 8: where = libswiftCore.dylib`swift_willThrow,address = 0x000000010e55ccc0

以此作为开端，希望读者能耐心看完，本文很长

准备工作

为了方便，我们先写好这样的一个Model类,定义个ErrorType，并且定义个实例方法抛出异常

enum CustomError:ErrorType{
    case LeoError1
    case LeoError2
}
class Person:NSObject{
    var name:String
    var age:UInt32
    init(name:String,age:UInt32){
        self.name = name
        self.age = age
    }
    //重写description是为了方便调试
    override var description:String{
        return "name:\(name) age:\(age)"
    }
    func PersonException() throws{
        throw CustomError.LeoError1
    }
}

然后在viewDidLoad中初始化一个对象，并打一个断点

let person = Person(name: "Leo",age: 23)

打印命令 p/po

(lldb) p person
(SwiftLLDBDemo.Person) $R0 = 0x00007f99b8d30b40 {
  ObjectiveC.NSObject = {
    isa = SwiftLLDBDemo.Person
  }
  name = "Leo"
  age = 23
}

(lldb) po person
name:Leo age:23

p命令会打印出对象的类型，如果是Objective C对象，会打印出isa，以及属性的值
po 命令对于继承自NSObject得对象，指示会打印出description中的内容

再举个例子

(lldb) po ["123","345"]
▿ 2 elements
  - [0] : "123"
  - [1] : "345"
 
(lldb) p ["123","345"]
([String]) $R2 = 2 values {
  [0] = "123"
  [1] = "345"
}

也可以，调用一段代码

(lldb) p for i in 1...3{ print(i) }
1
2
3

执行代码 e

expression命令可以帮助我们执行代码，

(lldb) e person.name = "Jack"
(lldb) p person
(SwiftLLDBDemo.Person) $R1 = 0x00007f9bf1424c20 {
  ObjectiveC.NSObject = {
    isa = SwiftLLDBDemo.Person
  }
  name = "Jack"
  age = 23
}

在这我们深入的研究所有命令

(lldb) help

内容太多，不拷贝进来了，自己在XCode里敲敲试试吧。

可以看到，有一部分是alias部分，有linux经验的同学应该知道，alias就是将一个简单的命令设置为复杂命令的别名。我们上面讲到的两个命令p/po就是两个alias命令

p         -- ('expression --')  Evaluate an expression (ObjC++ or Swift) in
               the current program context,using user defined variables and
               variables currently in scope.
  po        -- ('expression -O -- ')  Evaluate an expression (ObjC++ or Swift)
               in the current program context,using user defined variables and
               variables currently in scope.

所以，p命令，本质是expression -- ；po命令，本质是expression -O --

(lldb) expression -- person
(SwiftLLDBDemo.Person) $R0 = 0x00007f96a3f792d0 {
  ObjectiveC.NSObject = {
    isa = SwiftLLDBDemo.Person
  }
  name = "Leo"
  age = 23
}
(lldb) expression -O -- person
name:Leo age:23

更加复杂的执行

例如，动态的修改view的背景色

e self.view.backgroundColor = UIColor.blueColor

Expression命令很灵活

格式化打印 -f (format)

(lldb) expr -f bin -- person.age 
(UInt32) $R2 = 0b00000000000000000000000000010111
(lldb) expr -f oct -- person.age
(UInt32) $R3 = 027
(lldb) expr -f hex -- person.age
(UInt32) $R4 = 0x00000017

格式化打印可以更简单

(lldb) p/x person.age
(UInt32) $R5 = 0x00000017

打印Raw value expr -R -- 变量

(lldb) expr -R -- person
(SwiftLLDBDemo.Person) $R6 = 0x00007f96a3f792d0 { ObjectiveC.NSObject = {}
  name = { _core = { _baseAddress = { _rawValue = 0x0000000101041298 "Leo" }
      _countAndFlags = { value = 3 }
      _owner = None { Some = { instance_type = 0x0000000000000000 }
      }
    }
  }
  age = { value = 23 }
}

显示变量类型expr -T -- 变量

(lldb) expr -T -- person
(SwiftLLDBDemo.Person) $R7 = 0x00007f96a3f792d0 {
  (NSObject) ObjectiveC.NSObject = {
    (Class) isa = SwiftLLDBDemo.Person
  }
  (String) name = "Leo"
  (UInt32) age = 23
}

当然也可以结合多个使用expr -RRT -- person

帮助命令，可以再深入看看其他执行选项，不过不是很常用

help expression

LLDB变量

LLDB的变量和脚本语言类似，以美元符号开头，使用的时候也要带着美元符号，调用的时候和Swift的语法一致
例如

(lldb) e var $a = 10
(lldb) p $a
(Int) $a = 10
 
(lldb) e var $b = Person(name: "Jack",age: 25)
(lldb) p $b
(SWTest.Person) $b = 0x00007f8909539080 {
  ObjectiveC.NSObject = {
    isa = SWTest.Person
  }
  name = "Jack"
  age = 25
}

断点

断点采用这个命令breakpoint，缩写br
断点命令的文档较少，这里先列出文档

(lldb) help breakpoint
The following subcommands are supported:
 
      clear   -- Clears a breakpoint or set of breakpoints in the executable.
      command -- A set of commands for adding,removing and examining bits of
                 code to be executed when the breakpoint is hit (breakpoint
                 'commands').
      delete -- Delete the specified breakpoint(s). If no breakpoints are specified,delete them all. disable -- Disable the specified breakpoint(s) without removing them. If none are specified,disable all breakpoints. enable -- Enable the specified disabled breakpoint(s). If no breakpoints are specified,enable all of them. list -- List some or all breakpoints at configurable levels of detail. modify -- Modify the options on a breakpoint or set of breakpoints in the executable. If no breakpoint is specified,acts on the last created breakpoint. With the exception of -e,-d and -i,passing an empty argument clears the modification. name -- A set of commands to manage name tags for breakpoints set -- Sets a breakpoint or set of breakpoints in the executable.

breakpoint set -E language
breakpoint s -E swift -O ErrorType

列出断点

(lldb) br li
Current breakpoints:
1: file = '/Users/huangwenchen/Desktop/SWTest/SWTest/ViewController.swift',line = 27,locations = 1,resolved = 1,hit count = 1
 
  1.1: where = SWTest`SWTest.ViewController.viewDidLoad (SWTest.ViewController)() -> () + 75 at ViewController.swift:27,address = 0x000000010ef8556b,resolved,hit count = 1

禁用断点

(lldb) br dis 1
1 breakpoints disabled.

删除断点

(lldb) br del 1
1 breakpoints deleted; 0 breakpoint locations disabled.
(lldb) br li
No breakpoints currently set.

添加断点

(lldb) br set -f ViewController.swift -l 28
Breakpoint 2: where = SWTest`SWTest.ViewController.viewDidLoad (SWTest.ViewController)() -> () + 139 at ViewController.swift:29,address = 0x000000010ef855ab

也可以简写为

(lldb) b ViewController.swift:28
Breakpoint 3: where = SWTest`SWTest.ViewController.viewDidLoad (SWTest.ViewController)() -> () + 139 at ViewController.swift:29,address = 0x000000010ef855ab
(lldb) br li
Current breakpoints:
2: file = 'ViewController.swift',line = 28,hit count = 0
  2.1: where = SWTest`SWTest.ViewController.viewDidLoad (SWTest.ViewController)() -> () + 139 at ViewController.swift:29,address = 0x000000010ef855ab,hit count = 0 
 
3: file = 'ViewController.swift',hit count = 0
  3.1: where = SWTest`SWTest.ViewController.viewDidLoad (SWTest.ViewController)() -> () + 139 at ViewController.swift:29,hit count = 0

断点Name

断点名称是用来管理一组断点的，通过name可以启用或者禁用一组断点，一个断点可以有多个name，很像tag。

br set -f ViewController.swift -l 28 -N leo

(lldb) br set -f ViewController.swift -l 28 -N leo
Breakpoint 2: 3 locations.
(lldb) br li
Current breakpoints:
1: file = '/Users/huangwenchen/Desktop/SWTest/SWTest/ViewController.swift',line = 34,hit count = 1
 
  1.1: where = SWTest`SWTest.ViewController.viewDidLoad (SWTest.ViewController)() -> () + 75 at ViewController.swift:34,address = 0x00000001070d51fb,hit count = 1 
 
2: file = 'ViewController.swift',locations = 3,resolved = 3,hit count = 0
  Names:
    leo
 
  2.1: where = SWTest`SWTest.ViewController.__deallocating_deinit + 12 at ViewController.swift,address = 0x00000001070d538c,hit count = 0 
  2.2: where = SWTest`SWTest.ViewController.init (SWTest.ViewController.Type)(nibName : Swift.Optional<Swift.String>,bundle : Swift.Optional<__ObjC.NSBundle>) -> SWTest.ViewController + 57 at ViewController.swift,address = 0x00000001070d53f9,hit count = 0 
  2.3: where = SWTest`SWTest.ViewController.init (SWTest.ViewController.Type)(coder : __ObjC.NSCoder) -> Swift.Optional<SWTest.ViewController> + 16 at ViewController.swift,address = 0x00000001070d56d0,hit count = 0

在加上名字以后，我们就可以通过名字来操作断点了

(lldb) br disable -N leo
1 breakpoints disabled.

在某一个函数上加断点

例如，在准备Person的函数中personLoop添加断点

(lldb) br s -F personLoop
Breakpoint 2: 2 locations.
(lldb) br li
Current breakpoints:
1: file = '/Users/huangwenchen/Desktop/SWTest/SWTest/ViewController.swift',line = 40,hit count = 1
 
  1.1: where = SWTest`SWTest.ViewController.viewDidLoad (SWTest.ViewController)() -> () + 75 at ViewController.swift:40,address = 0x000000010f6d51bb,hit count = 1 
 
2: name = 'personLoop',locations = 2,resolved = 2,hit count = 0
  2.1: where = SWTest`SWTest.Person.personLoop (SWTest.Person)() -> () + 12 at ViewController.swift:25,address = 0x000000010f6d45cc,hit count = 0 
  2.2: where = SWTest`@objc SWTest.Person.personLoop (SWTest.Person)() -> () + 4 at ViewController.swift,address = 0x000000010f6d4664,hit count = 0

条件断点

先在这里加一个断点

当某种条件产生的时候触发的断点，例如停在1000次循环的第800次

然后添加条件，停在i == 80

(lldb) br li
Current breakpoints:
1: file = '/Users/huangwenchen/Desktop/SWTest/SWTest/ViewController.swift',address = 0x00000001094d81bb,hit count = 1 
 
2: file = '/Users/huangwenchen/Desktop/SWTest/SWTest/ViewController.swift',hit count = 1
 
  2.1: where = SWTest`SWTest.Person.personLoop (SWTest.Person)() -> () + 111 at ViewController.swift:27,address = 0x00000001094d762f,hit count = 1 
 
(lldb) br modify -c 'i == 80'
(lldb) po i
80

断点行为

当断点触发的时候，执行的LLDB代码

例如，当i==80的时候，输出sum

(lldb) br li
Current breakpoints:
1: file = '/Users/huangwenchen/Desktop/SWTest/SWTest/ViewController.swift',line = 40,hit count = 1
 
  1.1: where = SWTest`SWTest.ViewController.viewDidLoad (SWTest.ViewController)() -> () + 75 at ViewController.swift:40,address = 0x00000001057391bb,hit count = 1 
 
3: file = '/Users/huangwenchen/Desktop/SWTest/SWTest/ViewController.swift',line = 27,hit count = 0
 
  3.1: where = SWTest`SWTest.Person.personLoop (SWTest.Person)() -> () + 111 at ViewController.swift:27,address = 0x000000010573862f,hit count = 0 
 
(lldb) br modify -c 'i == 80' 3
(lldb) br command add 3
Enter your debugger command(s). Type 'DONE' to end.
> po sum
> DONE
 po sum
3160

其他断点相关

lldb中输入

(lldb) help br set

篇幅限制，不列出help的结果了

类型查找Type

抛出一个异常，不知道是啥的时候怎么办？

(lldb) type lookup CustomError
enum CustomError : ErrorType {
  case LeoError1
  case LeoError2
  var hashValue: Swift.Int {
    get {}
  }
  var _code: Swift.Int {
    get {}
  }
}

可以简写

(lldb) ty l CustomError
enum CustomError : ErrorType {
  case LeoError1
  case LeoError2
  var hashValue: Swift.Int {
    get {}
  }
  var _code: Swift.Int {
    get {}
  }
}

LLDB中的异常处理

执行一个抛出异常的方法

(lldb) e person.personException()
(SWTest.CustomError) $E0 = LeoError1

流程控制

frame info 查看当前所在的位置

(lldb) frame info
frame #0: 0x000000010573862f SWTest`SWTest.Person.personLoop (self=0x00007fbaf1d054d0)() -> () + 111 at ViewController.swift:27

c 继续运行
n next 下一行
s step in
finish step out

函数提前返回

thread return

通过这个命令，可以很好的隔离函数，通常用在函数的最开始位置，避免ARC引用计数问题

最后

欢饮关注我的CSDN博客，很长一段时间内，我会持续的更新iOS/Swift/Objective C相关的文章

LLDB调试的文章应该还有一篇进阶使用的，近期会更新