C언어 전처리

1 개념[ | ]

C언어 전처리
C Language Preprocessor
  • 코드 안의 '#'기호 명령 처리
  • 여러 줄의 경우 '\' 사용
  • 줄 끝에 ";"를 사용하지 않음
  • "x.c" 파일이 전처리 명령 처리를 하게 되면 "x.i"가 됨
  • 하나의 코드로 여러 제품을 개발 할 시 많이 사용됨

2 예시[ | ]

include 전처리
#include <stdio.h>

컴파일 이전에 #include <stdio.h> 명령이 먼저 처리가 됨. 즉, 컴파일 되기 전에 "stdio.h" 헤더 파일이 코드 형태로 추가되게 됨. 예를들면 a.c 파일이 있다면 전처리 후 a.i 파일로 변환됨. 자세한 내용은 C언어 컴파일 빌드 과정 참조

여러줄 전처리
  • 한 줄 표현
#define PI    3.14
  • 여러줄 표현
#define PI \    
             3.14

3 #include[ | ]

컴파일러에 설정되어 있는 디렉토리에서 찾음
#include <stdio.h>

'<', '>'로 감싸있는 경우 컴파일러에서 설정되어 있는 디렉토리에서 "stdio.h"를 찾음

현재 프로젝트 위치에서 찾음
#include "a.h"

현재 파일 위치에서 "a.h" 파일을 찾음

4 전처리 실험[ | ]

hello.c 코드의 전처리 명령 처리
  • 전처리만 처리하기 위한 gcc 명령
gcc -E -o hello.i hello.c
  • hello.c
#include <stdio.h>

void main()
{
    printf("Hello World\n");
}
  • hello.i
# 1 "e.c"
# 1 "<built-in>" 1
# 1 "<built-in>" 3
# 330 "<built-in>" 3
# 1 "<command line>" 1
# 1 "<built-in>" 2
# 1 "e.c" 2
# 1 "/usr/include/stdio.h" 1 3 4
# 64 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/sys/cdefs.h" 1 3 4
# 587 "/usr/include/sys/cdefs.h" 3 4
# 1 "/usr/include/sys/_symbol_aliasing.h" 1 3 4
# 588 "/usr/include/sys/cdefs.h" 2 3 4
# 653 "/usr/include/sys/cdefs.h" 3 4
# 1 "/usr/include/sys/_posix_availability.h" 1 3 4
# 654 "/usr/include/sys/cdefs.h" 2 3 4
# 65 "/usr/include/stdio.h" 2 3 4
# 1 "/usr/include/Availability.h" 1 3 4
# 190 "/usr/include/Availability.h" 3 4
# 1 "/usr/include/AvailabilityInternal.h" 1 3 4
# 191 "/usr/include/Availability.h" 2 3 4
# 66 "/usr/include/stdio.h" 2 3 4

# 1 "/usr/include/_types.h" 1 3 4
# 27 "/usr/include/_types.h" 3 4
# 1 "/usr/include/sys/_types.h" 1 3 4
# 33 "/usr/include/sys/_types.h" 3 4
# 1 "/usr/include/machine/_types.h" 1 3 4
# 32 "/usr/include/machine/_types.h" 3 4
# 1 "/usr/include/i386/_types.h" 1 3 4
# 37 "/usr/include/i386/_types.h" 3 4
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;
# 70 "/usr/include/i386/_types.h" 3 4
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;
# 33 "/usr/include/machine/_types.h" 2 3 4
# 34 "/usr/include/sys/_types.h" 2 3 4
# 55 "/usr/include/sys/_types.h" 3 4
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];


# 1 "/usr/include/sys/_pthread/_pthread_types.h" 1 3 4
# 57 "/usr/include/sys/_pthread/_pthread_types.h" 3 4
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;
# 81 "/usr/include/sys/_types.h" 2 3 4
# 28 "/usr/include/_types.h" 2 3 4
# 39 "/usr/include/_types.h" 3 4
typedef int __darwin_nl_item;
typedef int __darwin_wctrans_t;

typedef __uint32_t __darwin_wctype_t;
# 68 "/usr/include/stdio.h" 2 3 4



# 1 "/usr/include/sys/_types/_va_list.h" 1 3 4
# 31 "/usr/include/sys/_types/_va_list.h" 3 4
typedef __darwin_va_list va_list;
# 72 "/usr/include/stdio.h" 2 3 4
# 1 "/usr/include/sys/_types/_size_t.h" 1 3 4
# 30 "/usr/include/sys/_types/_size_t.h" 3 4
typedef __darwin_size_t size_t;
# 73 "/usr/include/stdio.h" 2 3 4
# 1 "/usr/include/sys/_types/_null.h" 1 3 4
# 74 "/usr/include/stdio.h" 2 3 4

# 1 "/usr/include/sys/stdio.h" 1 3 4
# 39 "/usr/include/sys/stdio.h" 3 4
int renameat(int, const char *, int, const char *) __attribute__((availability(macosx,introduced=10.10)));






int renamex_np(const char *, const char *, unsigned int) __attribute__((availability(macosx,introduced=10.12))) __attribute__((availability(ios,introduced=10.0))) __attribute__((availability(tvos,introduced=10.0))) __attribute__((availability(watchos,introduced=3.0)));
int renameatx_np(int, const char *, int, const char *, unsigned int) __attribute__((availability(macosx,introduced=10.12))) __attribute__((availability(ios,introduced=10.0))) __attribute__((availability(tvos,introduced=10.0))) __attribute__((availability(watchos,introduced=3.0)));
# 76 "/usr/include/stdio.h" 2 3 4

typedef __darwin_off_t fpos_t;
# 88 "/usr/include/stdio.h" 3 4
struct __sbuf {
 unsigned char *_base;
 int _size;
};


struct __sFILEX;
# 122 "/usr/include/stdio.h" 3 4
typedef struct __sFILE {
 unsigned char *_p;
 int _r;
 int _w;
 short _flags;
 short _file;
 struct __sbuf _bf;
 int _lbfsize;


 void *_cookie;
 int (* _Nullable _close)(void *);
 int (* _Nullable _read) (void *, char *, int);
 fpos_t (* _Nullable _seek) (void *, fpos_t, int);
 int (* _Nullable _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 FILE *__stdinp;
extern FILE *__stdoutp;
extern FILE *__stderrp;
# 231 "/usr/include/stdio.h" 3 4
void clearerr(FILE *);
int fclose(FILE *);
int feof(FILE *);
int ferror(FILE *);
int fflush(FILE *);
int fgetc(FILE *);
int fgetpos(FILE * restrict, fpos_t *);
char *fgets(char * restrict, int, FILE *);



FILE *fopen(const char * restrict __filename, const char * restrict __mode) __asm("_" "fopen" );

int fprintf(FILE * restrict, const char * restrict, ...) __attribute__((__format__ (__printf__, 2, 3)));
int fputc(int, FILE *);
int fputs(const char * restrict, FILE * restrict) __asm("_" "fputs" );
size_t fread(void * restrict __ptr, size_t __size, size_t __nitems, FILE * restrict __stream);
FILE *freopen(const char * restrict, const char * restrict,
                 FILE * restrict) __asm("_" "freopen" );
int fscanf(FILE * restrict, const char * restrict, ...) __attribute__((__format__ (__scanf__, 2, 3)));
int fseek(FILE *, long, int);
int fsetpos(FILE *, const fpos_t *);
long ftell(FILE *);
size_t fwrite(const void * restrict __ptr, size_t __size, size_t __nitems, FILE * restrict __stream) __asm("_" "fwrite" );
int getc(FILE *);
int getchar(void);
char *gets(char *);
void perror(const char *);
int printf(const char * restrict, ...) __attribute__((__format__ (__printf__, 1, 2)));
int putc(int, FILE *);
int putchar(int);
int puts(const char *);
int remove(const char *);
int rename (const char *__old, const char *__new);
void rewind(FILE *);
int scanf(const char * restrict, ...) __attribute__((__format__ (__scanf__, 1, 2)));
void setbuf(FILE * restrict, char * restrict);
int setvbuf(FILE * restrict, char * restrict, int, size_t);
int sprintf(char * restrict, const char * restrict, ...) __attribute__((__format__ (__printf__, 2, 3))) __attribute__((__availability__(swift, unavailable, message="Use snprintf instead.")));
int sscanf(const char * restrict, const char * restrict, ...) __attribute__((__format__ (__scanf__, 2, 3)));
FILE *tmpfile(void);

__attribute__((__availability__(swift, unavailable, message="Use mkstemp(3) instead.")))

__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 * restrict, const char * restrict, va_list) __attribute__((__format__ (__printf__, 2, 0)));
int vprintf(const char * restrict, va_list) __attribute__((__format__ (__printf__, 1, 0)));
int vsprintf(char * restrict, const char * restrict, va_list) __attribute__((__format__ (__printf__, 2, 0))) __attribute__((__availability__(swift, unavailable, message="Use vsnprintf instead.")));
# 297 "/usr/include/stdio.h" 3 4
char *ctermid(char *);





FILE *fdopen(int, const char *) __asm("_" "fdopen" );

int fileno(FILE *);
# 321 "/usr/include/stdio.h" 3 4
int pclose(FILE *) __attribute__((__availability__(swift, unavailable, message="Use posix_spawn APIs or NSTask instead.")));



FILE *popen(const char *, const char *) __asm("_" "popen" ) __attribute__((__availability__(swift, unavailable, message="Use posix_spawn APIs or NSTask instead.")));
# 342 "/usr/include/stdio.h" 3 4
int __srget(FILE *);
int __svfscanf(FILE *, const char *, va_list) __attribute__((__format__ (__scanf__, 2, 0)));
int __swbuf(int, FILE *);
# 353 "/usr/include/stdio.h" 3 4
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));
}
# 379 "/usr/include/stdio.h" 3 4
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__((__availability__(swift, unavailable, message="Use mkstemp(3) instead.")))

__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 *__dir, const char *__prefix) __asm("_" "tempnam" );
# 417 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/sys/_types/_off_t.h" 1 3 4
# 30 "/usr/include/sys/_types/_off_t.h" 3 4
typedef __darwin_off_t off_t;
# 418 "/usr/include/stdio.h" 2 3 4


int fseeko(FILE * __stream, off_t __offset, int __whence);
off_t ftello(FILE * __stream);





int snprintf(char * restrict __str, size_t __size, const char * restrict __format, ...) __attribute__((__format__ (__printf__, 3, 4)));
int vfscanf(FILE * restrict __stream, const char * restrict __format, va_list) __attribute__((__format__ (__scanf__, 2, 0)));
int vscanf(const char * restrict __format, va_list) __attribute__((__format__ (__scanf__, 1, 0)));
int vsnprintf(char * restrict __str, size_t __size, const char * restrict __format, va_list) __attribute__((__format__ (__printf__, 3, 0)));
int vsscanf(const char * restrict __str, const char * restrict __format, va_list) __attribute__((__format__ (__scanf__, 2, 0)));
# 442 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/sys/_types/_ssize_t.h" 1 3 4
# 30 "/usr/include/sys/_types/_ssize_t.h" 3 4
typedef __darwin_ssize_t ssize_t;
# 443 "/usr/include/stdio.h" 2 3 4


int dprintf(int, const char * restrict, ...) __attribute__((__format__ (__printf__, 2, 3))) __attribute__((availability(macosx,introduced=10.7)));
int vdprintf(int, const char * restrict, va_list) __attribute__((__format__ (__printf__, 2, 0))) __attribute__((availability(macosx,introduced=10.7)));
ssize_t getdelim(char ** restrict __linep, size_t * restrict __linecapp, int __delimiter, FILE * restrict __stream) __attribute__((availability(macosx,introduced=10.7)));
ssize_t getline(char ** restrict __linep, size_t * restrict __linecapp, FILE * restrict __stream) __attribute__((availability(macosx,introduced=10.7)));
# 458 "/usr/include/stdio.h" 3 4
extern const int sys_nerr;
extern const char *const sys_errlist[];

int asprintf(char ** restrict, const char * restrict, ...) __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 ** restrict, const char * restrict, va_list) __attribute__((__format__ (__printf__, 2, 0)));
FILE *zopen(const char *, const char *, int);





FILE *funopen(const void *,
                 int (* _Nullable)(void *, char *, int),
                 int (* _Nullable)(void *, const char *, int),
                 fpos_t (* _Nullable)(void *, fpos_t, int),
                 int (* _Nullable)(void *));
# 498 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/secure/_stdio.h" 1 3 4
# 31 "/usr/include/secure/_stdio.h" 3 4
# 1 "/usr/include/secure/_common.h" 1 3 4
# 32 "/usr/include/secure/_stdio.h" 2 3 4
# 42 "/usr/include/secure/_stdio.h" 3 4
extern int __sprintf_chk (char * restrict, int, size_t,
     const char * restrict, ...);
# 52 "/usr/include/secure/_stdio.h" 3 4
extern int __snprintf_chk (char * restrict, size_t, int, size_t,
      const char * restrict, ...);







extern int __vsprintf_chk (char * restrict, int, size_t,
      const char * restrict, va_list);







extern int __vsnprintf_chk (char * restrict, size_t, int, size_t,
       const char * restrict, va_list);
# 499 "/usr/include/stdio.h" 2 3 4
# 2 "e.c" 2

void main()
{
 printf("Hello World\n");
}

hello.c 파일의 전처리 명령 처리 후 hello.i 파일을 살펴보면 stdio.h의 코드들이 들어와 있는 것을 알 수 있음

5 같이 보기[ | ]

문서 댓글 ({{ doc_comments.length }})
{{ comment.name }} {{ comment.created | snstime }}