objc4源码编译与调试

源码下载

在Apple Open Source上选择对应自己的macOS版本下，下载objc4即可。

笔者是macOS Catalina 10.15.6，所以选择的是objc4-787.1版本，顺便在该页面中下载Libc，dyld，libauto，libclosure，libdispatch，libpthread，xnu，libplatform这几个依赖库，编译objc4的时候需要用到。

解决编译错误

下载完成，解压之后我们打开工程文件，运行报错unable to find sdk 'macosx.internal'

unable to find sdk 'macosx.internal'

解决方法：Project->Target->Build Settings->Base SDK选择macOS

解决unable to find sdk 'macosx.internal'

再次运行报错'sys/reason.h' file not found

'sys/reason.h' file not found

在项目目录下新建include/sys文件夹，将xnu-6153.141.1/bsd/sys/reason.h添加到该目录下再次编译。

这次报错是还是在objc-os.h文件中，提示'mach-o/dyld_priv.h' file not found

解决方法和上面一样，该文件在dyld-750.6/include/mach-o/dyld_priv.h路径。

运行后提示'os/lock_private.h' file not found，该文件在libplatform-220.100.1/private/os/lock_private.h路径，之后报错'os/base_private.h' file not found,也在该目录下。

再次运行后报错'pthread/tsd_private.h' file not found，该文件在libpthread-416.100.3/private/tsd_private.h

再次运行后报错'System/machine/cpu_capabilities.h' file not found，该文件在 xnu-6153.141.1/osfmk/machine/cpu_capabilities.h路径。

之后是报错'os/tsd.h' file not found，该文件在xnu-6153.141.1/libsyscall/os/tsd.h路径。

报错'pthread/spinlock_private.h' file not found,该文件在 libpthread-416.100.3/private/spinlock_private.h路径。

报错'System/pthread_machdep.h' file not found,该文件在只能在8.x级以前的版本中找到，LibC下载。

路径为 Libc-825.26/pthreads/pthread_machdep.h) 。该文件导入后会发现重复声明的报错以及宏定义重复的警告，报错为:

Typedef redefinition with different types ('int' vs 'volatile OSSpinLock' (aka 'volatile int'))

Static declaration of '_pthread_has_direct_tsd' follows non-static declaration

Static declaration of '_pthread_getspecific_direct' follows non-static declaration

Static declaration of '_pthread_setspecific_direct' follows non-static declaration

注释掉重复声明

注释重复声明2

注释重复声明3

注释重复宏1

注释重复宏3

再次运行报错'CrashReporterClient.h' file not found，该文件在Libc-825.26/include/CrashReporterClient.h

报错'_simple.h' file not found，该文件在libplatform-220.100.1/private/_simple.h路径。

报错'objc-shared-cache.h' file not found,该文件在dyld-750.6/include/objc-shared-cache.h路径。

报错Use of undeclared identifier 'DYLD_MACOSX_VERSION_10_11',在dyld_priv.h文件中添加下面的宏定义

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

报错Static_assert failed due to requirement 'bucketsMask >= ((unsigned long long)140737454800896ULL)' "Bucket field doesn't have enough bits for arbitrary pointers."，直接注释掉该断言。

报错Use of undeclared identifier 'CRGetCrashLogMessage',解决方法在Project->Target->Build Settings->Preprocessor Macros加入LIBC_NO_LIBCRASHREPORTERCLIENT

设置Preprocessor Macros

报错Mismatch in debug-ness macros,解决方法是将改行代码注释掉

报错'kern/restartable.h' file not found, 该文件在xnu-6153.141.1/osfmk/kern/restartable.h路径。

报错'Block_private.h' file not found,该文件在libclosure-74/Block_private.h路径。

报错can't open order file: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk/AppleInternal/OrderFiles/libobjc.order，解决方法是Project->Target->Build Settings->Order File添加路径$(SRCROOT)/libobjc.order。

报错library not found for -lCrashReporterClient,解决方法是在Project->Target->Build Settings->Other Linker Flags中删除lCrashReporterClient。

报错'_static_assert' declared as an array with a negative size，解决方法是直接注释掉该断言。

报错xcodebuild:1:1: SDK "macosx.internal" cannot be located.，解决方法修改Project->Target->Build Settings->Run Script(markgc) 中的macosx.internal,改为macosx。

到了这里我们发现已经可以BUILD SUCCESSED了。