iOS - lldb、 Clang、llvm我的理解

lldb

调试器，主要用于编程中调试 其中

快捷键有

命令	快捷功能
command+shift+y	暂停/继续
command+y	开启/关闭断点功能
command+shift+c	将光标切换到控制台
command+shift+y	隐藏/显示控制台
command+k	清空控制台

查询命令

p 、expresion -- 、print： 打印对应类型、地址信息、值 po、expresion --o -- ： 打印对象值

附：每次使用p后，lldb会自动分配变量，后边想继续使用这个变量，能够经过$后的数字取该变量

修改操做

e、expresion：修改变量，修改后，变量的地址也发生了改变

断点

1. 全局断点

出现异常会自动暂停 2. 符号断点Symbolic Breakpoint

当想知道方法testCalled何时调用时，添加对应的符号断点

3. watch point

观察对象、属性的改变

改变时会自动暂停到代码处并打印old value 和new value

4. tb 打印当前断点信息

(lldb) tb
Current breakpoints:
1: name = 'objc_exception_throw', locations = 1, resolved = 1, hit count = 0

  1.1: where = libobjc.A.dylib`objc_exception_throw, address = 0x00007fff20193fc5, resolved, hit count = 0 

2: names = {'[ViewController testCalled]', '[ViewController testCalled]', '[ViewController testCalled]'}, locations = 1, resolved = 1, hit count = 0

  2.1: where = LLDBDemo`-[ViewController testCalled] + 23 at ViewController.m:56:5, address = 0x000000010bea5dd7, resolved, hit count = 0 

3: file = '/Users/ternence/Documents/技术/面试技术练手Demo/LLDBDemo/LLDBDemo/ViewController.m', line = 21, exact_match = 0, locations = 1, resolved = 1, hit count = 1

  3.1: where = LLDBDemo`-[ViewController viewDidLoad] + 51 at ViewController.m:21:33, address = 0x000000010bea5be3, resolved, hit count = 1 

(lldb) 
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堆栈

1. bt thread backtrack 打印当前线程信息

(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 3.1
  * frame #0: 0x000000010bea5be3 LLDBDemo`-[ViewController viewDidLoad](self=0x00007fb2d7c0cd00, _cmd="viewDidLoad") at ViewController.m:21:33
    frame #1: 0x00007fff23f806a9 UIKitCore`-[UIViewController _sendViewDidLoadWithAppearanceProxyObjectTaggingEnabled] + 88
    frame #2: 0x00007fff23f8504c UIKitCore`-[UIViewController loadViewIfRequired] + 1084
    frame #3: 0x00007fff23f85436 UIKitCore`-[UIViewController view] + 27
    frame #4: 0x00007fff246ffc73 UIKitCore`-[UIWindow addRootViewControllerViewIfPossible] + 313
    frame #5: 0x00007fff246ff362 UIKitCore`-[UIWindow _updateLayerOrderingAndSetLayerHidden:actionBlock:] + 219
    frame #6: 0x00007fff24700325 UIKitCore`-[UIWindow _setHidden:forced:] + 362
    frame #7: 0x000000010e15a748 UIKit`-[UIWindowAccessibility _orderFrontWithoutMakingKey] + 84
    frame #8: 0x00007fff247133a6 UIKitCore`-[UIWindow _mainQueue_makeKeyAndVisible] + 42
    frame #9: 0x00007fff24951c05 UIKitCore`-[UIWindowScene _makeKeyAndVisibleIfNeeded] + 202
    frame #10: 0x00007fff23b0e80c UIKitCore`+[UIScene _sceneForFBSScene:create:withSession:connectionOptions:] + 1671
    frame #11: 0x00007fff246c2df9 UIKitCore`-[UIApplication _connectUISceneFromFBSScene:transitionContext:] + 1114
    frame #12: 0x00007fff246c3128 UIKitCore`-[UIApplication workspace:didCreateScene:withTransitionContext:completion:] + 289
    frame #13: 0x00007fff241a4ab4 UIKitCore`-[UIApplicationSceneClientAgent scene:didInitializeWithEvent:completion:] + 358
    frame #14: 0x00007fff25a1b40b FrontBoardServices`-[FBSScene _callOutQueue_agent_didCreateWithTransitionContext:completion:] + 398
    frame #15: 0x00007fff25a43e55 FrontBoardServices`__94-[FBSWorkspaceScenesClient createWithSceneID:groupID:parameters:transitionContext:completion:]_block_invoke.176 + 102
    frame #16: 0x00007fff25a28f12 FrontBoardServices`-[FBSWorkspace _calloutQueue_executeCalloutFromSource:withBlock:] + 209
    frame #17: 0x00007fff25a43b28 FrontBoardServices`__94-[FBSWorkspaceScenesClient createWithSceneID:groupID:parameters:transitionContext:completion:]_block_invoke + 352
    frame #18: 0x000000010c11b74e libdispatch.dylib`_dispatch_client_callout + 8
    frame #19: 0x000000010c11e656 libdispatch.dylib`_dispatch_block_invoke_direct + 295
    frame #20: 0x00007fff25a695d0 FrontBoardServices`__FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 30
    frame #21: 0x00007fff25a692b6 FrontBoardServices`-[FBSSerialQueue _targetQueue_performNextIfPossible] + 433
    frame #22: 0x00007fff25a6977b FrontBoardServices`-[FBSSerialQueue _performNextFromRunLoopSource] + 22
    frame #23: 0x00007fff20390ede CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
    frame #24: 0x00007fff20390dd6 CoreFoundation`__CFRunLoopDoSource0 + 180
    frame #25: 0x00007fff20390300 CoreFoundation`__CFRunLoopDoSources0 + 340
    frame #26: 0x00007fff2038a9f7 CoreFoundation`__CFRunLoopRun + 875
    frame #27: 0x00007fff2038a1a7 CoreFoundation`CFRunLoopRunSpecific + 567
    frame #28: 0x00007fff2b874d85 GraphicsServices`GSEventRunModal + 139
    frame #29: 0x00007fff246c14df UIKitCore`-[UIApplication _run] + 912
    frame #30: 0x00007fff246c639c UIKitCore`UIApplicationMain + 101
    frame #31: 0x000000010bea60e2 LLDBDemo`main(argc=1, argv=0x00007ffee3d59ca0) at main.m:17:12
    frame #32: 0x00007fff2025abbd libdyld.dylib`start + 1
(lldb) 
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2. **thread return**调试时在断点处return想要的值

执行后，条件语句会指向else里的NSLog(@"thread have return NO");

Clang

Clang项目为LLVM 项目的C语言系列(C，C ++，Objective C / C ++，OpenCL，CUDA和RenderScript)中的语言提供语言前端和工具基础结构。提供了与GCC兼容的编译器驱动程序(clang)和与MSVC兼容的编译器驱动程序(clang-cl.exe)