lldb的若干技巧及拾遗

机缘

以前有一阵觉得  chisel 真的挺好用的，后来翻看了历年的WWDC关于lldb的video 还是发现一些tips 

Tip

lldb 统一格式

• <noun> <verb> [options] [argument [argument ...]]

lldb 命令行都遵循上述格式，例如：

target create /bin/lsbreakpoint set —-name mallocprocess attach --pid 1234breakpoint set --file hello.c --line 100breakpoint modify —condition “self = $myModel"

lldb简写

help ->  h 
expression -O -- ->  po 
expression -- ->  p 
thread until 11 ->  th u 11 
breakpoint modify —condition "self = $myModel" ->  br m -c “self == $myModel"

lldb command alias

lldb 启动都会加载  ~/.lldbinit ，故而我们可以通过修改它来实现自己的增强 

例如  command alias ，常见的例子，譬如耳熟能详的  Reveal 能通过下列命令启动 

command alias reveal_load_sim expr (void*)dlopen("/Applications/Reveal.app/Contents/SharedSupport/iOS-Libraries/libReveal.dylib", 0x2);

我自己扩展了这个别名  pwv : 

command alias pwv expr (void)NSLog((NSString*)[[[UIApplication sharedApplication] keyWindow] recursiveDescription])

该命令可以打印keyWindow上的view的层级结构。

command regex

同样放在  ~/.lldbinit ，跟alias类似，不过可以带参数，使用正则。 

command regex pv 's/(.+)/expr (void)NSLog((NSString*)[(UIView*)%1 recursiveDescription])/'command regex postNoti 's/(.+)/expr (void)[[NSNotificationCenter defaultCenter] postNotificationName:%1 object:nil]/'

命令  pv %1 用来打印  %1 上的所有view的层级结构。 

命令  postNoti %1 用来post 一个notication如: 

(lldb) postNoti @"MyNotification"

根据日常开发的需要，  alias 和  regex 都可以用来当做打开/关闭某些扩展功能，如第三方的调试工具： 

打开/关闭FLEXcommand alias flex expr [[FLEXManager sharedManager] toggleExplorer]

regex 我用得也比较简单，基本跟alias差不多。相信还会有更geek的用法。 

command script

chisel就是用下列命令初始化的：

command script import /path/to/fblldb.py

• simple example

myCommands.py

def caflushCommand(debugger, command, result, internal_dict):debugger.HandleCommand("e (void)[CATransaction flush]")

command script import ~/myCommands.py

lldb关于python的接口我看得也不细，具体参见wwdc和lldb。chisel的github上也有讲。

流程控制

下列命令其意不言自明，日常其实不一定能用到，但  thread return 在debug时还是相当有用的，调试时发现某些bug，当重现步骤又太麻烦，不想修改代码后重新编译，可以在某些critical method中进行fake return。 

process continue continue c 
thread step-over next n 
thread step-in step s 
thread step-out finish

thread return

thread returnthread return NOthread return @"hi"

Examining Data

fr ame  v ariable 

(lldb) fr v self

(MyProject.ViewController) self = 0x00007fd63c221fa0 {UIKit.UIViewController = { 

UIResponder = {  NSObject = {    isa = AFTask.ViewController  }  _hasAlternateNextResponder = false  _hasInputAssistantItem = false}_overrideTransitioningDelegate = nil以下省略

其他拾遗

• 寄存器相关

(lldb) register readGeneral Purpose Registers:       rax = 0x0000000010004005       rbx = 0x00000000ffffffff       rcx = 0x00007fff5559b718       rdx = 0x0000000000000000       rdi = 0x00007fff5559b880       rsi = 0x0000000007000806       rbp = 0x00007fff5559b760       rsp = 0x00007fff5559b718        r8 = 0x0000000000001403        r9 = 0x00000000ffffffff       r10 = 0x0000000000000c00       r11 = 0x0000000000000206       r12 = 0x0000000000000c00       r13 = 0x0000000000000000       r14 = 0x00007fff5559b880       r15 = 0x0000000000001403       rip = 0x000000010e151386  libsystem_kernel.dylib`mach_msg_trap + 10    rflags = 0x0000000000000206        cs = 0x000000000000002b        fs = 0x0000000000000000        gs = 0x0000000000000000

• platform shell 
  在lldb中执行shell命令，如 

(lldb)platform shell ls

• objective-c set exception 断点

(lldb) br s -E objc

• 查看类型

(lldb) type lookup ErrorTypeprotocol ErrorType {  var _domain: Swift.String { get }  var _code: Swift.Int { get }}extension ErrorType {  var _domain: Swift.String {    get {}  }}

• 其他wwdc上有说修好了lldb的一些known issue，比如 

(lldb) p NSLog(@“%d”, i)error: 'NSLog' has unknown return type;  cast the call to its declared return typeerror: 1 errors parsing expression

(lldb) p [NSApplication sharedApplication].undoManager error: property ‘undoManager’ not found on object of type ‘id’error: 1 errors parsing expression

这些问题都修好了。

总结

其他的以后再补充。有些东西其实对于大多数开发者用处不大，大家随便看看。