iOS编译过后的代码，这个在理解oc内部实现比较有帮助

	#ifndef __OBJC2__
	#define __OBJC2__
	#endif
	struct objc_selector; struct objc_class;
	struct __rw_objc_super { 
		struct objc_object *object; 
		struct objc_object *superClass; 
		__rw_objc_super(struct objc_object *o, struct objc_object *s) : object(o), superClass(s) {} 
	};
	#ifndef _REWRITER_typedef_Protocol
	typedef struct objc_object Protocol;
	#define _REWRITER_typedef_Protocol
	#endif
	#define __OBJC_RW_DLLIMPORT extern
	__OBJC_RW_DLLIMPORT void objc_msgSend(void);
	__OBJC_RW_DLLIMPORT void objc_msgSendSuper(void);
	__OBJC_RW_DLLIMPORT void objc_msgSend_stret(void);
	__OBJC_RW_DLLIMPORT void objc_msgSendSuper_stret(void);
	__OBJC_RW_DLLIMPORT void objc_msgSend_fpret(void);
	__OBJC_RW_DLLIMPORT struct objc_class *objc_getClass(const char *);
	__OBJC_RW_DLLIMPORT struct objc_class *class_getSuperclass(struct objc_class *);
	__OBJC_RW_DLLIMPORT struct objc_class *objc_getMetaClass(const char *);
	__OBJC_RW_DLLIMPORT void objc_exception_throw( struct objc_object *);
	__OBJC_RW_DLLIMPORT int objc_sync_enter( struct objc_object *);
	__OBJC_RW_DLLIMPORT int objc_sync_exit( struct objc_object *);
	__OBJC_RW_DLLIMPORT Protocol *objc_getProtocol(const char *);
	#ifdef _WIN64
	typedef unsigned long long  _WIN_NSUInteger;
	#else
	typedef unsigned int _WIN_NSUInteger;
	#endif
	#ifndef __FASTENUMERATIONSTATE
	struct __objcFastEnumerationState {
		unsigned long state;
		void **itemsPtr;
		unsigned long *mutationsPtr;
		unsigned long extra[5];
	};
	__OBJC_RW_DLLIMPORT void objc_enumerationMutation(struct objc_object *);
	#define __FASTENUMERATIONSTATE
	#endif
	#ifndef __NSCONSTANTSTRINGIMPL
	struct __NSConstantStringImpl {
	  int *isa;
	  int flags;
	  char *str;
	  long length;
	};
	#ifdef CF_EXPORT_CONSTANT_STRING
	extern "C" __declspec(dllexport) int __CFConstantStringClassReference[];
	#else
	__OBJC_RW_DLLIMPORT int __CFConstantStringClassReference[];
	#endif
	#define __NSCONSTANTSTRINGIMPL
	#endif
	#ifndef BLOCK_IMPL
	#define BLOCK_IMPL
	struct __block_impl {
	  void *isa;
	  int Flags;
	  int Reserved;
	  void *FuncPtr;
	};
	// Runtime copy/destroy helper functions (from Block_private.h)
	#ifdef __OBJC_EXPORT_BLOCKS
	extern "C" __declspec(dllexport) void _Block_object_assign(void *, const void *, const int);
	extern "C" __declspec(dllexport) void _Block_object_dispose(const void *, const int);
	extern "C" __declspec(dllexport) void *_NSConcreteGlobalBlock[32];
	extern "C" __declspec(dllexport) void *_NSConcreteStackBlock[32];
	#else
	__OBJC_RW_DLLIMPORT void _Block_object_assign(void *, const void *, const int);
	__OBJC_RW_DLLIMPORT void _Block_object_dispose(const void *, const int);
	__OBJC_RW_DLLIMPORT void *_NSConcreteGlobalBlock[32];
	__OBJC_RW_DLLIMPORT void *_NSConcreteStackBlock[32];
	#endif
	#endif
	#define __block
	#define __weak
	
	#include <stdarg.h>
	struct __NSContainer_literal {
	  void * *arr;
	  __NSContainer_literal (unsigned int count, ...) {
		va_list marker;
		va_start(marker, count);
		arr = new void *[count];
		for (unsigned i = 0; i < count; i++)
		  arr[i] = va_arg(marker, void *);
		va_end( marker );
	  };
	  ~__NSContainer_literal() {
		delete[] arr;
	  }
	};
	extern "C" __declspec(dllimport) void * objc_autoreleasePoolPush(void);
	extern "C" __declspec(dllimport) void objc_autoreleasePoolPop(void *);
	
	struct __AtAutoreleasePool {
	  __AtAutoreleasePool() {atautoreleasepoolobj = objc_autoreleasePoolPush();}
	  ~__AtAutoreleasePool() {objc_autoreleasePoolPop(atautoreleasepoolobj);}
	  void * atautoreleasepoolobj;
	};
	
	#define __OFFSETOFIVAR__(TYPE, MEMBER) ((long long) &((TYPE *)0)->MEMBER)
	
	typedef signed char __int8_t;
	
	
	
	typedef unsigned char __uint8_t;
	typedef short __int16_t;
	typedef unsigned short __uint16_t;
	typedef int __int32_t;
	typedef unsigned int __uint32_t;
	typedef long long __int64_t;
	typedef unsigned long long __uint64_t;
	
	typedef long __darwin_intptr_t;
	typedef unsigned int __darwin_natural_t;
	typedef int __darwin_ct_rune_t;
	
	
	
	
	
	typedef union {
	 char __mbstate8[128];
	 long long _mbstateL;
	} __mbstate_t;
	
	typedef __mbstate_t __darwin_mbstate_t;
	
	
	typedef long int __darwin_ptrdiff_t;
	
	
	
	
	
	
	
	typedef long unsigned int __darwin_size_t;
	
	
	
	
	
	typedef __builtin_va_list __darwin_va_list;
	
	
	
	
	
	typedef int __darwin_wchar_t;
	
	
	
	
	typedef __darwin_wchar_t __darwin_rune_t;
	
	
	typedef int __darwin_wint_t;
	
	
	
	
	typedef unsigned long __darwin_clock_t;
	typedef __uint32_t __darwin_socklen_t;
	typedef long __darwin_ssize_t;
	typedef long __darwin_time_t;
	typedef __int64_t __darwin_blkcnt_t;
	typedef __int32_t __darwin_blksize_t;
	typedef __int32_t __darwin_dev_t;
	typedef unsigned int __darwin_fsblkcnt_t;
	typedef unsigned int __darwin_fsfilcnt_t;
	typedef __uint32_t __darwin_gid_t;
	typedef __uint32_t __darwin_id_t;
	typedef __uint64_t __darwin_ino64_t;
	
	typedef __darwin_ino64_t __darwin_ino_t;
	
	
	
	typedef __darwin_natural_t __darwin_mach_port_name_t;
	typedef __darwin_mach_port_name_t __darwin_mach_port_t;
	typedef __uint16_t __darwin_mode_t;
	typedef __int64_t __darwin_off_t;
	typedef __int32_t __darwin_pid_t;
	typedef __uint32_t __darwin_sigset_t;
	typedef __int32_t __darwin_suseconds_t;
	typedef __uint32_t __darwin_uid_t;
	typedef __uint32_t __darwin_useconds_t;
	typedef unsigned char __darwin_uuid_t[16];
	typedef char __darwin_uuid_string_t[37];
	
	
	struct __darwin_pthread_handler_rec {
	 void (*__routine)(void *);
	 void *__arg;
	 struct __darwin_pthread_handler_rec *__next;
	};
	
	struct _opaque_pthread_attr_t {
	 long __sig;
	 char __opaque[56];
	};
	
	struct _opaque_pthread_cond_t {
	 long __sig;
	 char __opaque[40];
	};
	
	struct _opaque_pthread_condattr_t {
	 long __sig;
	 char __opaque[8];
	};
	
	struct _opaque_pthread_mutex_t {
	 long __sig;
	 char __opaque[56];
	};
	
	struct _opaque_pthread_mutexattr_t {
	 long __sig;
	 char __opaque[8];
	};
	
	struct _opaque_pthread_once_t {
	 long __sig;
	 char __opaque[8];
	};
	
	struct _opaque_pthread_rwlock_t {
	 long __sig;
	 char __opaque[192];
	};
	
	struct _opaque_pthread_rwlockattr_t {
	 long __sig;
	 char __opaque[16];
	};
	
	struct _opaque_pthread_t {
	 long __sig;
	 struct __darwin_pthread_handler_rec *__cleanup_stack;
	 char __opaque[8176];
	};
	
	typedef struct _opaque_pthread_attr_t __darwin_pthread_attr_t;
	typedef struct _opaque_pthread_cond_t __darwin_pthread_cond_t;
	typedef struct _opaque_pthread_condattr_t __darwin_pthread_condattr_t;
	typedef unsigned long __darwin_pthread_key_t;
	typedef struct _opaque_pthread_mutex_t __darwin_pthread_mutex_t;
	typedef struct _opaque_pthread_mutexattr_t __darwin_pthread_mutexattr_t;
	typedef struct _opaque_pthread_once_t __darwin_pthread_once_t;
	typedef struct _opaque_pthread_rwlock_t __darwin_pthread_rwlock_t;
	typedef struct _opaque_pthread_rwlockattr_t __darwin_pthread_rwlockattr_t;
	typedef struct _opaque_pthread_t *__darwin_pthread_t;
	typedef int __darwin_nl_item;
	typedef int __darwin_wctrans_t;
	
	typedef __uint32_t __darwin_wctype_t;
	
	
	
	typedef __darwin_va_list va_list;
	typedef __darwin_size_t size_t;
	
	extern "C" {
	
	int renameat(int, const char *, int, const char *) __attribute__((availability(macosx,introduced=10.10)));
	
	}
	
	typedef __darwin_off_t fpos_t;
	struct __sbuf {
	 unsigned char *_base;
	 int _size;
	};
	
	
	struct __sFILEX;
	typedef struct __sFILE {
	 unsigned char *_p;
	 int _r;
	 int _w;
	 short _flags;
	 short _file;
	 struct __sbuf _bf;
	 int _lbfsize;
	
	
	 void *_cookie;
	 int (*_close)(void *);
	 int (*_read) (void *, char *, int);
	 fpos_t (*_seek) (void *, fpos_t, int);
	 int (*_write)(void *, const char *, int);
	
	
	 struct __sbuf _ub;
	 struct __sFILEX *_extra;
	 int _ur;
	
	
	 unsigned char _ubuf[3];
	 unsigned char _nbuf[1];
	
	
	 struct __sbuf _lb;
	
	
	 int _blksize;
	 fpos_t _offset;
	} FILE;
	
	extern "C" {
	extern FILE *__stdinp;
	extern FILE *__stdoutp;
	extern FILE *__stderrp;
	}
	extern "C" {
	void clearerr(FILE *);
	int fclose(FILE *);
	int feof(FILE *);
	int ferror(FILE *);
	int fflush(FILE *);
	int fgetc(FILE *);
	int fgetpos(FILE * , fpos_t *);
	char *fgets(char * , int, FILE *);
	
	
	
	FILE *fopen(const char * , const char * ) __asm("_" "fopen");
	
	int fprintf(FILE * , const char * , ...) __attribute__((__format__ (__printf__, 2, 3)));
	int fputc(int, FILE *);
	int fputs(const char * , FILE * ) __asm("_" "fputs") ;
	size_t fread(void * , size_t, size_t, FILE * );
	FILE *freopen(const char * , const char * ,
	                 FILE * ) __asm("_" "freopen") ;
	int fscanf(FILE * , const char * , ...) __attribute__((__format__ (__scanf__, 2, 3)));
	int fseek(FILE *, long, int);
	int fsetpos(FILE *, const fpos_t *);
	long ftell(FILE *);
	size_t fwrite(const void * , size_t, size_t, FILE * ) __asm("_" "fwrite") ;
	int getc(FILE *);
	int getchar(void);
	char *gets(char *);
	void perror(const char *);
	int printf(const char * , ...) __attribute__((__format__ (__printf__, 1, 2)));
	int putc(int, FILE *);
	int putchar(int);
	int puts(const char *);
	int remove(const char *);
	int rename (const char *, const char *);
	void rewind(FILE *);
	int scanf(const char * , ...) __attribute__((__format__ (__scanf__, 1, 2)));
	void setbuf(FILE * , char * );
	int setvbuf(FILE * , char * , int, size_t);
	int sprintf(char * , const char * , ...) __attribute__((__format__ (__printf__, 2, 3)));
	int sscanf(const char * , const char * , ...) __attribute__((__format__ (__scanf__, 2, 3)));
	FILE *tmpfile(void);
	
	
	__attribute__((deprecated("This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of tmpnam(3), it is highly recommended that you use mkstemp(3) instead.")))
	
	char *tmpnam(char *);
	int ungetc(int, FILE *);
	int vfprintf(FILE * , const char * , va_list) __attribute__((__format__ (__printf__, 2, 0)));
	int vprintf(const char * , va_list) __attribute__((__format__ (__printf__, 1, 0)));
	int vsprintf(char * , const char * , va_list) __attribute__((__format__ (__printf__, 2, 0)));
	}
	extern "C" {
	
	
	
	char *ctermid(char *);
	
	
	
	
	
	FILE *fdopen(int, const char *) __asm("_" "fdopen");
	
	int fileno(FILE *);
	}
	extern "C" {
	int pclose(FILE *);
	
	
	
	FILE *popen(const char *, const char *) __asm("_" "popen");
	
	}
	extern "C" {
	int __srget(FILE *);
	int __svfscanf(FILE *, const char *, va_list) __attribute__((__format__ (__scanf__, 2, 0)));
	int __swbuf(int, FILE *);
	}
	
	
	
	
	
	
	
	inline __attribute__ ((__always_inline__)) int __sputc(int _c, FILE *_p) {
	 if (--_p->_w >= 0 || (_p->_w >= _p->_lbfsize && (char)_c != '\n'))
	  return (*_p->_p++ = _c);
	 else
	  return (__swbuf(_c, _p));
	}
	extern "C" {
	void flockfile(FILE *);
	int ftrylockfile(FILE *);
	void funlockfile(FILE *);
	int getc_unlocked(FILE *);
	int getchar_unlocked(void);
	int putc_unlocked(int, FILE *);
	int putchar_unlocked(int);
	
	
	
	int getw(FILE *);
	int putw(int, FILE *);
	
	
	
	__attribute__((deprecated("This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of tempnam(3), it is highly recommended that you use mkstemp(3) instead.")))
	
	char *tempnam(const char *, const char *) __asm("_" "tempnam") ;
	}
	typedef __darwin_off_t off_t;
	
	extern "C" {
	int fseeko(FILE *, off_t, int);
	off_t ftello(FILE *);
	}
	
	
	
	extern "C" {
	int snprintf(char * , size_t, const char * , ...) __attribute__((__format__ (__printf__, 3, 4)));
	int vfscanf(FILE * , const char * , va_list) __attribute__((__format__ (__scanf__, 2, 0)));
	int vscanf(const char * , va_list) __attribute__((__format__ (__scanf__, 1, 0)));
	int vsnprintf(char * , size_t, const char * , va_list) __attribute__((__format__ (__printf__, 3, 0)));
	int vsscanf(const char * , const char * , va_list) __attribute__((__format__ (__scanf__, 2, 0)));
	}
	typedef __darwin_ssize_t ssize_t;
	
	extern "C" {
	int dprintf(int, const char * , ...) __attribute__((__format__ (__printf__, 2, 3))) __attribute__((availability(macosx,introduced=10.7)));
	int vdprintf(int, const char * , va_list) __attribute__((__format__ (__printf__, 2, 0))) __attribute__((availability(macosx,introduced=10.7)));
	ssize_t getdelim(char ** , size_t * , int, FILE * ) __attribute__((availability(macosx,introduced=10.7)));
	ssize_t getline(char ** , size_t * , FILE * ) __attribute__((availability(macosx,introduced=10.7)));
	}
	
	
	
	
	
	
	
	extern "C" {
	extern const int sys_nerr;
	extern const char *const sys_errlist[];
	
	int asprintf(char ** , const char * , ...) __attribute__((__format__ (__printf__, 2, 3)));
	char *ctermid_r(char *);
	char *fgetln(FILE *, size_t *);
	const char *fmtcheck(const char *, const char *);
	int fpurge(FILE *);
	void setbuffer(FILE *, char *, int);
	int setlinebuf(FILE *);
	int vasprintf(char ** , const char * , va_list) __attribute__((__format__ (__printf__, 2, 0)));
	FILE *zopen(const char *, const char *, int);
	
	
	
	
	
	FILE *funopen(const void *,
	                 int (*)(void *, char *, int),
	                 int (*)(void *, const char *, int),
	                 fpos_t (*)(void *, fpos_t, int),
	                 int (*)(void *));
	}
	
	
	
	struct __main_block_impl_0 {
	  struct __block_impl impl;
	  struct __main_block_desc_0* Desc;
	  __main_block_impl_0(void *fp, struct __main_block_desc_0 *desc, int flags=0) {
	    impl.isa = &_NSConcreteStackBlock;
	    impl.Flags = flags;
	    impl.FuncPtr = fp;
	    Desc = desc;
	  }
	};
	static void __main_block_func_0(struct __main_block_impl_0 *__cself) {
	
	}
	
	static struct __main_block_desc_0 {
	  size_t reserved;
	  size_t Block_size;
	} __main_block_desc_0_DATA = { 0, sizeof(struct __main_block_impl_0)};
	int main(){
	    void(*blk)(void) = (void (*)())&__main_block_impl_0((void *)__main_block_func_0, &__main_block_desc_0_DATA);
	
	    ((void (*)(__block_impl *))((__block_impl *)blk)->FuncPtr)((__block_impl *)blk);
	}
	static struct IMAGE_INFO { unsigned version; unsigned flag; } _OBJC_IMAGE_INFO = { 0, 2 };