objc4

This project is a buildable and debuggable version of latest Objective-C runtime (objc4-781) on Apple Open Source

• Requirement
• Installation
• Usage
• objc4 tarballs
• Build Phases
• Build Setting
• License

Requirement

Installation

Manually

Download zip or clone this repo, select objc scheme and build.

Usage

After building the objc scheme, manually integrate generated libobjc.A.dylib into your project manually. Or you can use objc-inspect scheme which is a preset inspector for debugging objc4 runtime.

objc4 tarballs

• objc4-781
• xnu-6153.41.3
• Libc-1353.41.1
• dyld-733.6
• libauto-187.tar.gz
• libclosure-74
• libdispatch-1173.40.5
• libplatform-220
• libpthread-416.40.3

Build Phases

Private Header

objc header	#include	tarball
objc-os.h	#include <sys/reason.h>	/xnu-6153.41.3/bsd/sys/reason.h
objc-os.h	#include <mach-o/dyld_priv.h>	/dyld-733.6/include/mach-o/dyld_priv.h
objc-os.h	#include <os/lock_private.h>	/libplatform-220/private/os/lock_private.h
lock_private.h	#include <os/base_private.h>	/libplatform-220/private/os/base_private.h
objc-os.h	#include <System/pthread_machdep.h>	removed in latest Libc tarball (Libc-1353.41.1), this header should be commented-out
pthread_machdep.h	#include <System/machine/cpu_capabilities.h>	/xnu-6153.41.3/osfmk/machine/cpu_capabilities.h
objc-os.h	#include <pthread/workqueue_private.h>	/libpthread-416.40.3/private/workqueue_private.h
objc-os.h	#include <objc-shared-cache.h>	/dyld-733.6/include/objc-shared-cache.h
objc-errors.mm	#include <_simple.h>	/libplatform-220/private/_simple.h
objc-block-trampolines.mm	#include <Block_private.h>	/libclosure-74/Block_private.h
objc-os.h	#include <crt_externs.h>	/Libc-1353.41.1/include/crt_externs.h
objc-runtime-new.mm	#include <mach/shared_region.h>	/xnu-6153.41.3/osfmk/mach/shared_region.h
objc-cache.mm	#include <kern/restartable.h>	/xnu-6153.41.3/osfmk/mach/restartable.defs, build from xnu kernel
objc-os.h	#include <CrashReporterClient.h>	/Libc-825.24/include/CrashReporterClient.h

Private Header Included Header

private header	#include	tarball
tsd_private.h	#include <os/tsd.h>	/xnu-6153.41.3/libsyscall/os/tsd.h
tsd_private.h	#include <pthread/spinlock_private.h>	/libpthread-416.40.3/private/spinlock_private.h
lock_private.h	#include <pthread/tsd_private.h>	/libpthread-416.40.3/private/tsd_private.h
workqueue_private.h	#include <pthread/qos_private.h>	/llibpthread-416.40.3/private/qos_private.h
qos_private.h	#include <sys/qos_private.h>	/libpthread-416.40.3/sys/qos_private.h

Bridge OS

In public macosx sdk (latest Xcode 11.3.1), bridgeos (e.g. __has_feature(attribute_availability_bridgeos)) is unavailable, bridgeos availability should be removed or commented-out.

dyld

In latest dyld-733.6 (dyld-421.2 later), apple use this ruby script to expand versions, platfrom versions from a versionSets which defined in a YAML file, code generated by this script will be inserted after @MAC_VERSION_DEFS@, @IOS_VERSION_DEFS@, @WATCHOS_VERSION_DEFS@, @TVOS_VERSION_DEFS@ and @BRIDGEOS_VERSION_DEFS@ in dyld_priv.h. For more detail please refer to dyld.

XNU

<kern/restartable.h> is generated form restartable.defs in xnu tarball during building xun kernel, which is a little different from the one that shipped with public sdk that located in /Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/Frameworks/Kernel.framework/Versions/A/Headers/kern/restartable.h.

Build Setting

Declaration	Value
HEADER_SEARCH_PATHS	$(SRCROOT)/../macosx.internal/System/Library/Frameworks/System.framework/PrivateHeaders
GCC_PREPROCESSOR_DEFINITIONS	LIBC_NO_LIBCRASHREPORTERCLIENT
ORDER_FILE	$(SRCROOT)/libobjc.order
OTHER_LDFLAGS[sdk=macosx*]	-lc++abi -Xlinker -sectalign -Xlinker __DATA -Xlinker __objc_data -Xlinker 0x1000 -Xlinker -interposable_list -Xlinker interposable.txt
OTHER_LDFLAGS[sdk=iphoneos*][arch=*]	-lc++abi -Wl,-segalign,0x4000 -Xlinker -sectalign -Xlinker __DATA -Xlinker __objc_data -Xlinker 0x1000 -Xlinker -interposable_list -Xlinker interposable.txt -isystem -iframework
OTHER_LDFLAGS[sdk=iphonesimulator*][arch=*]	-lc++abi -Xlinker -interposable_list -Xlinker interposable.txt

Run Script

Evidently public macosx sdk is our only choice, we need to update value of parameter -sdk from macosx.internal to macosx in run script of objc target.

License

This project is released under the MIT License. The objc4 project is released under the APPLE PUBLIC SOURCE LICENSE Version 2.0.