OC源码编译，可直接运行、调试，通过它可以更好的理解OC的本质以及底层实现

本项目中使用的是苹果源码 objc4-781 版本， 系统版本为macos 10.15 ，可以从 苹果开源源码 和 官方tarballs 查看相关源码和依赖库， 所使用的到的依赖库如下：

libdispatch、libpthread、dyld、Libc、libplatform、libauto、libclosure、xnu

以上项目可直接编译使用！如需自己编译，可查看以下步骤！否则可忽略以下步骤！

苹果源码编译问题与解决方案

1. macosx.internal 报错

unable to find sdk 'macosx.internal'

• 将 Build Settings -> Base SDK 设置为 macos 10.15
• 将 Valid Architectures 删除 i386 架构支持

2. file not found 报错

• 在工程目录下新建 Common 文件夹
• 之后在 Xcode -> Build Setting -> Header Search Paths 添加 $(SRCROOT)/Common
• 在Common文件夹中新建sys文件夹，并从下载的其他的包中找到 reason.h ，放到sys文件夹中即可
  
• 以下同理
  

'sys/reason.h' file not found

'mach-o/dyld_priv.h' file not found

'os/lock_private.h' file not found

'os/base_private.h' file not found

'pthread/tsd_private.h' file not found

'System/machine/cpu_capabilities.h' file not found

'os/tsd.h' file not found

'pthread/spinlock_private.h' file not found

'System/pthread_machdep.h' file not found

'CrashReporterClient.h' file not found

'objc-shared-cache.h' file not found

'_simple.h' file not found

'kern/restartable.h' file not found

'Block_private.h' file not found

'objc/objc-block-trampolines.h' file not found

3. bridgeos(3.0) 报错

• 删除bridgeos(3.0)即可

4. OS_UNFAIR_LOCK_ADAPTIVE_SPIN 报错

Use of undeclared identifier 'OS_UNFAIR_LOCK_ADAPTIVE_SPIN'

将此处修改为os_unfair_lock_lock(&mLock);

5. Use of undeclared identifier xxx

Use of undeclared identifier 'DYLD_MACOSX_VERSION_10_11'

Use of undeclared identifier 'DYLD_MACOSX_VERSION_10_14'

Use of undeclared identifier 'DYLD_MACOSX_VERSION_10_13'

Use of undeclared identifier 'DYLD_MACOSX_VERSION_10_12'

定义以下宏即可

#define DYLD_MACOSX_VERSION_10_11 0x000A0B00
#define DYLD_MACOSX_VERSION_10_14 0x000A0E00
#define DYLD_MACOSX_VERSION_10_13 0x000A0D00
#define DYLD_MACOSX_VERSION_10_12 0x000A0C00

6. OrderFiles/libobjc.order 报错

Can't open order file: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk/AppleInternal/OrderFiles/libobjc.order

将 Build Settings - Order file 路径改为 $(SRCROOT)/libobjc.order 即可

7. -lCrashReporterClient 报错

ld: library not found for -lCrashReporterClient

将 Build Settings - other link flags 删除 -lCrashReporterClient 即可

8. Script 报错

/xcodebuild:1:1: SDK "macosx.internal" cannot be located.
/xcrun:1:1: sh -c '/Applications/Xcode.app/Contents/Developer/usr/bin/xcodebuild -sdk macosx.internal -find clang++ 2> /dev/null' failed with exit code 16384: (null) (errno=No such file or directory)
/xcrun:1:1: unable to find utility "clang++", not a developer tool or in PATH

将 Build Phases - Run Script(markc) 中 macosx.internal 改为 macosx

9. 新建target测试即可使用

依赖库图

附注

github 图片不显示配置（亲测可用）

sudo /etc/hosts

将以下内容添加到 hosts 文件即可

140.82.114.3      github.com
199.232.69.194    github.global.ssl.fastly.net
185.199.110.153   assets-cdn.github.com
140.82.114.3      gist.github.com

199.232.28.133    raw.githubusercontent.com
199.232.28.133    gist.githubusercontent.com
199.232.28.133    cloud.githubusercontent.com
199.232.28.133    camo.githubusercontent.com
199.232.28.133    avatars0.githubusercontent.com
199.232.28.133    avatars1.githubusercontent.com
199.232.28.133    avatars2.githubusercontent.com
199.232.28.133    avatars3.githubusercontent.com