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kingcos / Perspective

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Xcode 中的 Link Map 文件 #75

Open kingcos opened 5 years ago

kingcos commented 5 years ago
Date Notes Xcode
2019-04-01 首次提交 10.1

Preface

Link Map File，译作链接映射文件（下文将称 Link Map 文件）。在构建可执行文件之前，需要先编译为目标文件（Object File），并链接所需要的其他库，那么 Link Map 文件就记录了链接器（Linker）在链接过程中产生的一些信息，本文将谈谈这个文件的构成。

What

Xcode 中默认是不会将 Link Map 文件在构建时暴露出来的，需要我们手动在「Build Settings」-「Write Link Map File」-「Yes」打开该写入该文件的设置。这样当我们再次编译项目，默认就可以在 ~/Library/Developer/Xcode/DerivedData/<TARGET_NAME>-<Random_ID>/Build/Intermediates.noindex/<TARGET_NAME>.build/Debug-<Device_Type>/<TARGET_NAME>.build/<TARGET_NAME>-LinkMap-normal-<Arch>.txt 中找到。如有更改 Link Map 文件路径的需求也可以在「Path to Link Map File」中更改。

举个例子，我的 DemoiOS 项目中 Link Map 文件的完整路径为：/Users/kingcos/Library/Developer/Xcode/DerivedData/DemoiOS-hifhuapijabsaxgpelrpiwhbzlqv/Build/Intermediates.noindex/DemoiOS.build/Debug-iphonesimulator/DemoiOS.build/DemoiOS-LinkMap-normal-x86_64.txt。

How

下面来分析一下 Link Map 文件的构成。

Path

# Path: /Users/kingcos/Library/Developer/Xcode/DerivedData/DemoiOS-hifhuapijabsaxgpelrpiwhbzlqv/Build/Products/Debug-iphonesimulator/DemoiOS.app/DemoiOS

Path 为最终生成「可执行文件」的路径。

Arch

// Target: Simulator
# Arch: x86_64

// Target: iPhone
# Arch: arm64

Arch 为「可执行文件」的架构，具体架构与设备的对照可参考下表：

Device System Arch
iOS 模拟器 iOS x86_64
搭载 A7 及以上的 iOS 真机 iOS arm64（A12 架构为「arm64e」，但 Link Map 文件尚未体现）
搭载 A7 以下的 iOS 真机 iOS armv7
Apple Watch 模拟器 watchOS i386
Apple Watch 真机 watchOS armv7s/arm64_32（Apple Watch S4 为「arm64_32」）
Mac macOS x86_64

Object files

# Object files:
[  0] linker synthesized
[  1] /Users/kingcos/Library/Developer/Xcode/DerivedData/DemoiOS-hifhuapijabsaxgpelrpiwhbzlqv/Build/Intermediates.noindex/DemoiOS.build/Debug-iphonesimulator/DemoiOS.build/DemoiOS.app-Simulated.xcent
[  2] /Users/kingcos/Library/Developer/Xcode/DerivedData/DemoiOS-hifhuapijabsaxgpelrpiwhbzlqv/Build/Intermediates.noindex/DemoiOS.build/Debug-iphonesimulator/DemoiOS.build/Objects-normal/x86_64/ViewController.o
[  3] /Users/kingcos/Library/Developer/Xcode/DerivedData/DemoiOS-hifhuapijabsaxgpelrpiwhbzlqv/Build/Intermediates.noindex/DemoiOS.build/Debug-iphonesimulator/DemoiOS.build/Objects-normal/x86_64/main.o
[  4] /Users/kingcos/Library/Developer/Xcode/DerivedData/DemoiOS-hifhuapijabsaxgpelrpiwhbzlqv/Build/Intermediates.noindex/DemoiOS.build/Debug-iphonesimulator/DemoiOS.build/Objects-normal/x86_64/AppDelegate.o
[  5] /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/System/Library/Frameworks//Foundation.framework/Foundation.tbd
[  6] /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/usr/lib/libobjc.tbd
[  7] /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.1.sdk/System/Library/Frameworks//UIKit.framework/UIKit.tbd

Object files 为「目标文件」，该部分列出了所有的目标文件、记录系统动态库信息的文件等，其中第一列为序号，也对应了下面「Symbols」部分中的「File」一列。

No. File Notes
0 linker synthesized 链接器合成所需要的数据。
1 DemoiOS.app-Simulated.xcent xcent 是 XML 1.0 文档文本文件，可以使用编辑器直接打开。其中存储了 application-identifier 和 keychain-access-groups，但该行仅在模拟器作为构建目标时存在。
2~4 *.o 编译后的目标文件
5~7 *.tbd tbd 是文本基础（Text-based）文件，也可以用编辑器打开，其中包含了动态库的信息，例如系统 Foundation.tbd 如下图

Sections

# Sections:
# Address   Size        Segment Section
0x100001730 0x00000333  __TEXT  __text           // 代码段
0x100001A64 0x0000002A  __TEXT  __stubs          // 符号桩
0x100001A90 0x00000056  __TEXT  __stub_helper    // 辅助函数
0x100001AE6 0x00000A27  __TEXT  __objc_methname  // 方法名
0x10000250D 0x0000003C  __TEXT  __objc_classname // 类名
0x100002549 0x0000086D  __TEXT  __objc_methtype  // 方法类型
0x100002DB6 0x0000007A  __TEXT  __cstring        // 字符串
0x100002E30 0x0000017A  __TEXT  __entitlements
0x100002FAC 0x00000048  __TEXT  __unwind_info    // 存储处理异常的信息
0x100003000 0x00000010  __DATA  __nl_symbol_ptr  // 非懒绑定的指针符号表
0x100003010 0x00000010  __DATA  __got
0x100003020 0x00000038  __DATA  __la_symbol_ptr  // 懒绑定的指针符号表
0x100003058 0x00000010  __DATA  __objc_classlist // 类列表
0x100003068 0x00000010  __DATA  __objc_protolist // 协议列表
0x100003078 0x00000008  __DATA  __objc_imageinfo // 镜像信息
0x100003080 0x00000BE8  __DATA  __objc_const     // 常量
0x100003C68 0x00000010  __DATA  __objc_selrefs   // selector 引用
0x100003C78 0x00000008  __DATA  __objc_classrefs // 类引用
0x100003C80 0x00000008  __DATA  __objc_superrefs // 父类引用
0x100003C88 0x00000008  __DATA  __objc_ivar      // 成员变量
0x100003C90 0x000000A0  __DATA  __objc_data      // 数据
0x100003D30 0x000000C0  __DATA  __data           // 数据段

Sections 中主要描述了节（Section）相关的信息，分为四列：内存地址、大小、段（Segment）、节。每一行的地址为上一行初始地址 + 内存大小（+ 偏移量）。__TEXT 和 __DATA 标示了段信息，并各自对应多个节信息。__TEXT 为只读代码段，存储了可执行的代码信息，__DATA 为数据段，存储了可读写但不可执行的数据。关于此处更为详细的信息，之后将在「Mach-O」专题中讲述。

Symbols

# Symbols:
# Address   Size        File  Name
0x100001730 0x0000003C  [  2] -[ViewController viewDidLoad]
0x100001770 0x00000092  [  3] _main
0x100001810 0x00000080  [  4] -[AppDelegate application:didFinishLaunchingWithOptions:]
0x100001890 0x00000040  [  4] -[AppDelegate applicationWillResignActive:]
0x1000018D0 0x00000040  [  4] -[AppDelegate applicationDidEnterBackground:]
0x100001910 0x00000040  [  4] -[AppDelegate applicationWillEnterForeground:]
0x100001950 0x00000040  [  4] -[AppDelegate applicationDidBecomeActive:]
0x100001990 0x00000040  [  4] -[AppDelegate applicationWillTerminate:]
0x1000019D0 0x00000020  [  4] -[AppDelegate window]
0x1000019F0 0x00000040  [  4] -[AppDelegate setWindow:]
0x100001A30 0x00000033  [  4] -[AppDelegate .cxx_destruct]
0x100001A64 0x00000006  [  5] _NSStringFromClass
0x100001A6A 0x00000006  [  7] _UIApplicationMain
0x100001A70 0x00000006  [  6] _objc_autoreleasePoolPop
0x100001A76 0x00000006  [  6] _objc_autoreleasePoolPush
0x100001A7C 0x00000006  [  6] _objc_msgSendSuper2
0x100001A82 0x00000006  [  6] _objc_retainAutoreleasedReturnValue
0x100001A88 0x00000006  [  6] _objc_storeStrong
0x100001A90 0x00000010  [  0] helper helper
0x100001AA0 0x0000000A  [  5] _NSStringFromClass
0x100001AAA 0x0000000A  [  6] _objc_autoreleasePoolPop
0x100001AB4 0x0000000A  [  6] _objc_autoreleasePoolPush
0x100001ABE 0x0000000A  [  6] _objc_msgSendSuper2
0x100001AC8 0x0000000A  [  6] _objc_retainAutoreleasedReturnValue
0x100001AD2 0x0000000A  [  6] _objc_storeStrong
0x100001ADC 0x0000000A  [  7] _UIApplicationMain
0x100001AE6 0x0000000C  [  2] literal string: viewDidLoad
0x100001AF2 0x00000006  [  3] literal string: class
0x100001AF8 0x00000009  [  4] literal string: isEqual:
0x100001B01 0x00000005  [  4] literal string: self
0x100001B06 0x00000011  [  4] literal string: performSelector:
0x100001B17 0x0000001C  [  4] literal string: performSelector:withObject:
0x100001B33 0x00000027  [  4] literal string: performSelector:withObject:withObject:
0x100001B5A 0x00000008  [  4] literal string: isProxy
0x100001B62 0x0000000F  [  4] literal string: isKindOfClass:
0x100001B71 0x00000011  [  4] literal string: isMemberOfClass:
0x100001B82 0x00000014  [  4] literal string: conformsToProtocol:
0x100001B96 0x00000014  [  4] literal string: respondsToSelector:
0x100001BAA 0x00000007  [  4] literal string: retain
0x100001BB1 0x00000008  [  4] literal string: release
0x100001BB9 0x0000000C  [  4] literal string: autorelease
0x100001BC5 0x0000000C  [  4] literal string: retainCount
0x100001BD1 0x00000005  [  4] literal string: zone
0x100001BD6 0x00000005  [  4] literal string: hash
0x100001BDB 0x0000000B  [  4] literal string: superclass
0x100001BE6 0x0000000C  [  4] literal string: description
0x100001BF2 0x00000011  [  4] literal string: debugDescription
0x100001C03 0x0000001F  [  4] literal string: applicationDidFinishLaunching:
0x100001C22 0x0000002C  [  4] literal string: application:willFinishLaunchingWithOptions:
0x100001C4E 0x0000002B  [  4] literal string: application:didFinishLaunchingWithOptions:
0x100001C79 0x0000001C  [  4] literal string: applicationDidBecomeActive:
0x100001C95 0x0000001D  [  4] literal string: applicationWillResignActive:
0x100001CB2 0x0000001B  [  4] literal string: application:handleOpenURL:
0x100001CCD 0x00000032  [  4] literal string: application:openURL:sourceApplication:annotation:
0x100001CFF 0x0000001D  [  4] literal string: application:openURL:options:
0x100001D1C 0x00000024  [  4] literal string: applicationDidReceiveMemoryWarning:
0x100001D40 0x0000001A  [  4] literal string: applicationWillTerminate:
0x100001D5A 0x00000022  [  4] literal string: applicationSignificantTimeChange:
0x100001D7C 0x00000035  [  4] literal string: application:willChangeStatusBarOrientation:duration:
0x100001DB1 0x0000002B  [  4] literal string: application:didChangeStatusBarOrientation:
0x100001DDC 0x00000026  [  4] literal string: application:willChangeStatusBarFrame:
0x100001E02 0x00000025  [  4] literal string: application:didChangeStatusBarFrame:
0x100001E27 0x00000031  [  4] literal string: application:didRegisterUserNotificationSettings:
0x100001E58 0x0000003E  [  4] literal string: application:didRegisterForRemoteNotificationsWithDeviceToken:
0x100001E96 0x0000003E  [  4] literal string: application:didFailToRegisterForRemoteNotificationsWithError:
0x100001ED4 0x0000002A  [  4] literal string: application:didReceiveRemoteNotification:
0x100001EFE 0x00000029  [  4] literal string: application:didReceiveLocalNotification:
0x100001F27 0x0000004F  [  4] literal string: application:handleActionWithIdentifier:forLocalNotification:completionHandler:
0x100001F76 0x00000061  [  4] literal string: application:handleActionWithIdentifier:forRemoteNotification:withResponseInfo:completionHandler:
0x100001FD7 0x00000050  [  4] literal string: application:handleActionWithIdentifier:forRemoteNotification:completionHandler:
0x100002027 0x00000060  [  4] literal string: application:handleActionWithIdentifier:forLocalNotification:withResponseInfo:completionHandler:
0x100002087 0x00000041  [  4] literal string: application:didReceiveRemoteNotification:fetchCompletionHandler:
0x1000020C8 0x0000002F  [  4] literal string: application:performFetchWithCompletionHandler:
0x1000020F7 0x0000003C  [  4] literal string: application:performActionForShortcutItem:completionHandler:
0x100002133 0x00000043  [  4] literal string: application:handleEventsForBackgroundURLSession:completionHandler:
0x100002176 0x00000032  [  4] literal string: application:handleWatchKitExtensionRequest:reply:
0x1000021A8 0x0000002D  [  4] literal string: applicationShouldRequestHealthAuthorization:
0x1000021D5 0x0000002C  [  4] literal string: application:handleIntent:completionHandler:
0x100002201 0x0000001F  [  4] literal string: applicationDidEnterBackground:
0x100002220 0x00000020  [  4] literal string: applicationWillEnterForeground:
0x100002240 0x0000002F  [  4] literal string: applicationProtectedDataWillBecomeUnavailable:
0x10000226F 0x0000002C  [  4] literal string: applicationProtectedDataDidBecomeAvailable:
0x10000229B 0x00000035  [  4] literal string: application:supportedInterfaceOrientationsForWindow:
0x1000022D0 0x00000031  [  4] literal string: application:shouldAllowExtensionPointIdentifier:
0x100002301 0x0000003F  [  4] literal string: application:viewControllerWithRestorationIdentifierPath:coder:
0x100002340 0x00000028  [  4] literal string: application:shouldSaveApplicationState:
0x100002368 0x0000002B  [  4] literal string: application:shouldRestoreApplicationState:
0x100002393 0x00000030  [  4] literal string: application:willEncodeRestorableStateWithCoder:
0x1000023C3 0x0000002F  [  4] literal string: application:didDecodeRestorableStateWithCoder:
0x1000023F2 0x0000002E  [  4] literal string: application:willContinueUserActivityWithType:
0x100002420 0x00000035  [  4] literal string: application:continueUserActivity:restorationHandler:
0x100002455 0x00000039  [  4] literal string: application:didFailToContinueUserActivityWithType:error:
0x10000248E 0x00000023  [  4] literal string: application:didUpdateUserActivity:
0x1000024B1 0x00000034  [  4] literal string: application:userDidAcceptCloudKitShareWithMetadata:
0x1000024E5 0x00000007  [  4] literal string: window
0x1000024EC 0x0000000B  [  4] literal string: setWindow:
0x1000024F7 0x0000000E  [  4] literal string: .cxx_destruct
0x100002505 0x00000008  [  4] literal string: _window
0x10000250D 0x0000000F  [  2] literal string: ViewController
0x10000251C 0x0000000C  [  4] literal string: AppDelegate
0x100002528 0x00000016  [  4] literal string: UIApplicationDelegate
0x10000253E 0x00000009  [  4] literal string: NSObject
0x100002547 0x00000002  [  4] literal string: 
0x100002549 0x00000008  [  2] literal string: v16@0:8
0x100002551 0x0000000B  [  4] literal string: B24@0:8@16
0x10000255C 0x00000008  [  4] literal string: #16@0:8
0x100002564 0x00000008  [  4] literal string: @16@0:8
0x10000256C 0x0000000B  [  4] literal string: @24@0:8:16
0x100002577 0x0000000E  [  4] literal string: @32@0:8:16@24
0x100002585 0x00000011  [  4] literal string: @40@0:8:16@24@32
0x100002596 0x00000008  [  4] literal string: B16@0:8
0x10000259E 0x0000000B  [  4] literal string: B24@0:8#16
0x1000025A9 0x0000000B  [  4] literal string: B24@0:8:16
0x1000025B4 0x00000009  [  4] literal string: Vv16@0:8
0x1000025BD 0x00000008  [  4] literal string: Q16@0:8
0x1000025C5 0x00000012  [  4] literal string: ^{_NSZone=}16@0:8
0x1000025D7 0x00000015  [  4] literal string: B24@0:8@"Protocol"16
0x1000025EC 0x00000012  [  4] literal string: @"NSString"16@0:8
0x1000025FE 0x0000000B  [  4] literal string: v24@0:8@16
0x100002609 0x0000000E  [  4] literal string: B32@0:8@16@24
0x100002617 0x00000014  [  4] literal string: B48@0:8@16@24@32@40
0x10000262B 0x00000011  [  4] literal string: B40@0:8@16@24@32
0x10000263C 0x00000011  [  4] literal string: v40@0:8@16q24d32
0x10000264D 0x0000000E  [  4] literal string: v32@0:8@16q24
0x10000265B 0x0000002D  [  4] literal string: v56@0:8@16{CGRect={CGPoint=dd}{CGSize=dd}}24
0x100002688 0x0000000E  [  4] literal string: v32@0:8@16@24
0x100002696 0x00000015  [  4] literal string: v48@0:8@16@24@32@?40
0x1000026AB 0x00000018  [  4] literal string: v56@0:8@16@24@32@40@?48
0x1000026C3 0x00000012  [  4] literal string: v40@0:8@16@24@?32
0x1000026D5 0x0000000F  [  4] literal string: v32@0:8@16@?24
0x1000026E4 0x0000000E  [  4] literal string: Q32@0:8@16@24
0x1000026F2 0x00000011  [  4] literal string: @40@0:8@16@24@32
0x100002703 0x00000012  [  4] literal string: B40@0:8@16@24@?32
0x100002715 0x00000011  [  4] literal string: v40@0:8@16@24@32
0x100002726 0x0000001A  [  4] literal string: v24@0:8@"UIApplication"16
0x100002740 0x0000002B  [  4] literal string: B32@0:8@"UIApplication"16@"NSDictionary"24
0x10000276B 0x00000024  [  4] literal string: B32@0:8@"UIApplication"16@"NSURL"24
0x10000278F 0x00000034  [  4] literal string: B48@0:8@"UIApplication"16@"NSURL"24@"NSString"32@40
0x1000027C3 0x00000035  [  4] literal string: B40@0:8@"UIApplication"16@"NSURL"24@"NSDictionary"32
0x1000027F8 0x00000020  [  4] literal string: v40@0:8@"UIApplication"16q24d32
0x100002818 0x0000001D  [  4] literal string: v32@0:8@"UIApplication"16q24
0x100002835 0x0000003C  [  4] literal string: v56@0:8@"UIApplication"16{CGRect={CGPoint=dd}{CGSize=dd}}24
0x100002871 0x00000039  [  4] literal string: v32@0:8@"UIApplication"16@"UIUserNotificationSettings"24
0x1000028AA 0x00000025  [  4] literal string: v32@0:8@"UIApplication"16@"NSData"24
0x1000028CF 0x00000026  [  4] literal string: v32@0:8@"UIApplication"16@"NSError"24
0x1000028F5 0x0000002B  [  4] literal string: v32@0:8@"UIApplication"16@"NSDictionary"24
0x100002920 0x00000032  [  4] literal string: v32@0:8@"UIApplication"16@"UILocalNotification"24
0x100002952 0x00000048  [  4] literal string: v48@0:8@"UIApplication"16@"NSString"24@"UILocalNotification"32@?<v@?>40
0x10000299A 0x00000052  [  4] literal string: v56@0:8@"UIApplication"16@"NSString"24@"NSDictionary"32@"NSDictionary"40@?<v@?>48
0x1000029EC 0x00000041  [  4] literal string: v48@0:8@"UIApplication"16@"NSString"24@"NSDictionary"32@?<v@?>40
0x100002A2D 0x00000059  [  4] literal string: v56@0:8@"UIApplication"16@"NSString"24@"UILocalNotification"32@"NSDictionary"40@?<v@?>48
0x100002A86 0x00000035  [  4] literal string: v40@0:8@"UIApplication"16@"NSDictionary"24@?<v@?Q>32
0x100002ABB 0x00000024  [  4] literal string: v32@0:8@"UIApplication"16@?<v@?Q>24
0x100002ADF 0x00000042  [  4] literal string: v40@0:8@"UIApplication"16@"UIApplicationShortcutItem"24@?<v@?B>32
0x100002B21 0x00000030  [  4] literal string: v40@0:8@"UIApplication"16@"NSString"24@?<v@?>32
0x100002B51 0x00000043  [  4] literal string: v40@0:8@"UIApplication"16@"NSDictionary"24@?<v@?@"NSDictionary">32
0x100002B94 0x00000043  [  4] literal string: v40@0:8@"UIApplication"16@"INIntent"24@?<v@?@"INIntentResponse">32
0x100002BD7 0x00000027  [  4] literal string: Q32@0:8@"UIApplication"16@"UIWindow"24
0x100002BFE 0x00000027  [  4] literal string: B32@0:8@"UIApplication"16@"NSString"24
0x100002C25 0x00000044  [  4] literal string: @"UIViewController"40@0:8@"UIApplication"16@"NSArray"24@"NSCoder"32
0x100002C69 0x00000026  [  4] literal string: B32@0:8@"UIApplication"16@"NSCoder"24
0x100002C8F 0x00000026  [  4] literal string: v32@0:8@"UIApplication"16@"NSCoder"24
0x100002CB5 0x00000040  [  4] literal string: B40@0:8@"UIApplication"16@"NSUserActivity"24@?<v@?@"NSArray">32
0x100002CF5 0x00000033  [  4] literal string: v40@0:8@"UIApplication"16@"NSString"24@"NSError"32
0x100002D28 0x0000002D  [  4] literal string: v32@0:8@"UIApplication"16@"NSUserActivity"24
0x100002D55 0x0000002E  [  4] literal string: v32@0:8@"UIApplication"16@"CKShareMetadata"24
0x100002D83 0x00000012  [  4] literal string: @"UIWindow"16@0:8
0x100002D95 0x00000015  [  4] literal string: v24@0:8@"UIWindow"16
0x100002DAA 0x0000000C  [  4] literal string: @"UIWindow"
0x100002DB6 0x00000005  [  4] literal string: hash
0x100002DBB 0x00000005  [  4] literal string: TQ,R
0x100002DC0 0x0000000B  [  4] literal string: superclass
0x100002DCB 0x00000005  [  4] literal string: T#,R
0x100002DD0 0x0000000C  [  4] literal string: description
0x100002DDC 0x00000011  [  4] literal string: T@"NSString",R,C
0x100002DED 0x00000011  [  4] literal string: debugDescription
0x100002DFE 0x00000007  [  4] literal string: window
0x100002E05 0x00000011  [  4] literal string: T@"UIWindow",&,N
0x100002E16 0x0000001A  [  4] literal string: T@"UIWindow",&,N,V_window
0x100002E30 0x0000017A  [  1] opaque_section
0x100002FAC 0x00000048  [  0] compact unwind info
0x100003000 0x00000008  [  0] non-lazy-pointer-to-local: dyld_stub_binder
0x100003008 0x00000008  [  0] non-lazy-pointer
0x100003010 0x00000008  [  0] non-lazy-pointer-to-local: _objc_msgSend
0x100003018 0x00000008  [  0] non-lazy-pointer-to-local: _objc_release
0x100003020 0x00000008  [  5] _NSStringFromClass
0x100003028 0x00000008  [  7] _UIApplicationMain
0x100003030 0x00000008  [  6] _objc_autoreleasePoolPop
0x100003038 0x00000008  [  6] _objc_autoreleasePoolPush
0x100003040 0x00000008  [  6] _objc_msgSendSuper2
0x100003048 0x00000008  [  6] _objc_retainAutoreleasedReturnValue
0x100003050 0x00000008  [  6] _objc_storeStrong
0x100003058 0x00000008  [  2] anon
0x100003060 0x00000008  [  4] anon
0x100003068 0x00000008  [  4] l_OBJC_LABEL_PROTOCOL_$_NSObject
0x100003070 0x00000008  [  4] l_OBJC_LABEL_PROTOCOL_$_UIApplicationDelegate
0x100003078 0x00000008  [  0] objc image info
0x100003080 0x00000048  [  2] l_OBJC_METACLASS_RO_$_ViewController
0x1000030C8 0x00000020  [  2] l_OBJC_$_INSTANCE_METHODS_ViewController
0x1000030E8 0x00000048  [  2] l_OBJC_CLASS_RO_$_ViewController
0x100003130 0x000001D0  [  4] l_OBJC_$_PROTOCOL_INSTANCE_METHODS_NSObject
0x100003300 0x00000020  [  4] l_OBJC_$_PROTOCOL_INSTANCE_METHODS_OPT_NSObject
0x100003320 0x00000048  [  4] l_OBJC_$_PROP_LIST_NSObject
0x100003368 0x000000A0  [  4] l_OBJC_$_PROTOCOL_METHOD_TYPES_NSObject
0x100003408 0x00000018  [  4] l_OBJC_$_PROTOCOL_REFS_UIApplicationDelegate
0x100003420 0x000004A0  [  4] l_OBJC_$_PROTOCOL_INSTANCE_METHODS_OPT_UIApplicationDelegate
0x1000038C0 0x00000018  [  4] l_OBJC_$_PROP_LIST_UIApplicationDelegate
0x1000038D8 0x00000188  [  4] l_OBJC_$_PROTOCOL_METHOD_TYPES_UIApplicationDelegate
0x100003A60 0x00000018  [  4] l_OBJC_CLASS_PROTOCOLS_$_AppDelegate
0x100003A78 0x00000048  [  4] l_OBJC_METACLASS_RO_$_AppDelegate
0x100003AC0 0x000000E0  [  4] l_OBJC_$_INSTANCE_METHODS_AppDelegate
0x100003BA0 0x00000028  [  4] l_OBJC_$_INSTANCE_VARIABLES_AppDelegate
0x100003BC8 0x00000058  [  4] l_OBJC_$_PROP_LIST_AppDelegate
0x100003C20 0x00000048  [  4] l_OBJC_CLASS_RO_$_AppDelegate
0x100003C68 0x00000008  [  2] pointer-to-literal-cstring
0x100003C70 0x00000008  [  3] pointer-to-literal-cstring
0x100003C78 0x00000008  [  3] objc-class-ref
0x100003C80 0x00000008  [  2] anon
0x100003C88 0x00000008  [  4] _OBJC_IVAR_$_AppDelegate._window
0x100003C90 0x00000028  [  2] _OBJC_CLASS_$_ViewController
0x100003CB8 0x00000028  [  2] _OBJC_METACLASS_$_ViewController
0x100003CE0 0x00000028  [  4] _OBJC_METACLASS_$_AppDelegate
0x100003D08 0x00000028  [  4] _OBJC_CLASS_$_AppDelegate
0x100003D30 0x00000060  [  4] l_OBJC_PROTOCOL_$_NSObject
0x100003D90 0x00000060  [  4] l_OBJC_PROTOCOL_$_UIApplicationDelegate

Symbols 中为符号（Symbol）相关的信息，分为四列：内存地址、大小、文件（序号对应 Object files 中的文件）、符号名称。通过结合「Sections」部分可以得知每一节的具体符号内容，并可以计算某个类或文件编译后的大小，帮助我们分析包体积。

Dead Stripped Symbols

# Dead Stripped Symbols:
#           Size        File  Name
<<dead>>    0x00000018  [  2] CIE
<<dead>>    0x00000018  [  3] CIE
<<dead>>    0x00000006  [  4] literal string: class
<<dead>>    0x00000008  [  4] literal string: v16@0:8
<<dead>>    0x00000018  [  4] CIE

Dead Stripped Symbols 也是和上面结构一致的符号表，但「Dead」意味着表里的符号已经不再存在，因此没有记录内存地址。

Reference