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  • C程序编译过程

    • 1.1程序被其他程序翻译成不同的格式

      1.hello.c

    #include <stdio.h>
    
    int main()
    {
         printf("hello world
    ");           
    }

      2.编译过程



      3.编译系统
        预处理器、编译器、汇编器和链接器一起构成了编译系统

      预处理阶段。预处理器(cpp)根据以字符#开通的命令,修改原始的C程序。比如hello.c中第1行的#include<stdio.h>命令告诉预处理器读取系统头文件stdio.h的内容,并把它直接插入到程序的文本中。结果就得到了另一个C程序,通常是以.i作为文件扩展名

      预处理的过程主要处理包括以下过程:

    • 将所有的#define删除,并且展开所有的宏定义
    • 处理所有的条件预编译指令,比如#if #ifdef #elif #else #endif等
    • 处理#include 预编译指令,将被包含的文件插入到该预编译指令的位置。
    • 删除所有注释 “//”和”/* */”.
    • 添加行号和文件标识,以便编译时产生调试用的行号及编译错误警告行号。
    • 保留所有的#pragma编译器指令,因为编译器需要使用它们

      通常使用以下命令来进行预处理:

      gcc -E hello.c -o hello.i

      参数-E表示只进行预处理 或者也可以使用以下指令完成预处理过程

      cpp hello.c > hello.i      /*  cpp – The C Preprocessor  */

      1 # 1 "hello.c"
      2 # 1 "<built-in>"
      3 # 1 "<command-line>"
      4 # 1 "hello.c"
      5 # 1 "/usr/include/stdio.h" 1 3 4
      6 # 28 "/usr/include/stdio.h" 3 4
      7 # 1 "/usr/include/features.h" 1 3 4
      8 # 324 "/usr/include/features.h" 3 4
      9 # 1 "/usr/include/x86_64-linux-gnu/bits/predefs.h" 1 3 4
     10 # 325 "/usr/include/features.h" 2 3 4
     11 # 357 "/usr/include/features.h" 3 4
     12 # 1 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 1 3 4
     13 # 378 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 3 4
     14 # 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4
     15 # 379 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 2 3 4
     16 # 358 "/usr/include/features.h" 2 3 4
     17 # 389 "/usr/include/features.h" 3 4
     18 # 1 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 1 3 4
     19 
     20 
     21 
     22 # 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4
     23 # 5 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 2 3 4
     24 
     25 
     26 
     27 
     28 # 1 "/usr/include/x86_64-linux-gnu/gnu/stubs-64.h" 1 3 4
     29 # 10 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 2 3 4
     30 # 390 "/usr/include/features.h" 2 3 4
     31 # 29 "/usr/include/stdio.h" 2 3 4
     32 
     33 
     34 
     35 
     36 
     37 # 1 "/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stddef.h" 1 3 4
     38 # 212 "/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stddef.h" 3 4
     39 typedef long unsigned int size_t;
     40 # 35 "/usr/include/stdio.h" 2 3 4
     41 
     42 # 1 "/usr/include/x86_64-linux-gnu/bits/types.h" 1 3 4
     43 # 28 "/usr/include/x86_64-linux-gnu/bits/types.h" 3 4
     44 # 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4
     45 # 29 "/usr/include/x86_64-linux-gnu/bits/types.h" 2 3 4
     46 
     47 
     48 typedef unsigned char __u_char;
     49 typedef unsigned short int __u_short;
     50 typedef unsigned int __u_int;
     51 typedef unsigned long int __u_long;
     52 
     53 
     54 typedef signed char __int8_t;
     55 typedef unsigned char __uint8_t;
     56 typedef signed short int __int16_t;
     57 typedef unsigned short int __uint16_t;
     58 typedef signed int __int32_t;
     59 typedef unsigned int __uint32_t;
     60 
     61 typedef signed long int __int64_t;
     62 typedef unsigned long int __uint64_t;
     63 
     64 
     65 
     66 
     67 
     68 
     69 
     70 typedef long int __quad_t;
     71 typedef unsigned long int __u_quad_t;
     72 # 131 "/usr/include/x86_64-linux-gnu/bits/types.h" 3 4
     73 # 1 "/usr/include/x86_64-linux-gnu/bits/typesizes.h" 1 3 4
     74 # 132 "/usr/include/x86_64-linux-gnu/bits/types.h" 2 3 4
     75 
     76 
     77 typedef unsigned long int __dev_t;
     78 typedef unsigned int __uid_t;
     79 typedef unsigned int __gid_t;
     80 typedef unsigned long int __ino_t;
     81 typedef unsigned long int __ino64_t;
     82 typedef unsigned int __mode_t;
     83 typedef unsigned long int __nlink_t;
     84 typedef long int __off_t;
     85 typedef long int __off64_t;
     86 typedef int __pid_t;
     87 typedef struct { int __val[2]; } __fsid_t;
     88 typedef long int __clock_t;
     89 typedef unsigned long int __rlim_t;
     90 typedef unsigned long int __rlim64_t;
     91 typedef unsigned int __id_t;
     92 typedef long int __time_t;
     93 typedef unsigned int __useconds_t;
     94 typedef long int __suseconds_t;
     95 
     96 typedef int __daddr_t;
     97 typedef long int __swblk_t;
     98 typedef int __key_t;
     99 
    100 
    101 typedef int __clockid_t;
    102 
    103 
    104 typedef void * __timer_t;
    105 
    106 
    107 typedef long int __blksize_t;
    108 
    109 
    110 
    111 
    112 typedef long int __blkcnt_t;
    113 typedef long int __blkcnt64_t;
    114 
    115 
    116 typedef unsigned long int __fsblkcnt_t;
    117 typedef unsigned long int __fsblkcnt64_t;
    118 
    119 
    120 typedef unsigned long int __fsfilcnt_t;
    121 typedef unsigned long int __fsfilcnt64_t;
    122 
    123 typedef long int __ssize_t;
    124 
    125 
    126 
    127 typedef __off64_t __loff_t;
    128 typedef __quad_t *__qaddr_t;
    129 typedef char *__caddr_t;
    130 
    131 
    132 typedef long int __intptr_t;
    133 
    134 
    135 typedef unsigned int __socklen_t;
    136 # 37 "/usr/include/stdio.h" 2 3 4
    137 # 45 "/usr/include/stdio.h" 3 4
    138 struct _IO_FILE;
    139 
    140 
    141 
    142 typedef struct _IO_FILE FILE;
    143 
    144 
    145 
    146 
    147 
    148 # 65 "/usr/include/stdio.h" 3 4
    149 typedef struct _IO_FILE __FILE;
    150 # 75 "/usr/include/stdio.h" 3 4
    151 # 1 "/usr/include/libio.h" 1 3 4
    152 # 32 "/usr/include/libio.h" 3 4
    153 # 1 "/usr/include/_G_config.h" 1 3 4
    154 # 15 "/usr/include/_G_config.h" 3 4
    155 # 1 "/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stddef.h" 1 3 4
    156 # 16 "/usr/include/_G_config.h" 2 3 4
    157 
    158 
    159 
    160 
    161 # 1 "/usr/include/wchar.h" 1 3 4
    162 # 83 "/usr/include/wchar.h" 3 4
    163 typedef struct
    164 {
    165   int __count;
    166   union
    167   {
    168 
    169     unsigned int __wch;
    170 
    171 
    172 
    173     char __wchb[4];
    174   } __value;
    175 } __mbstate_t;
    176 # 21 "/usr/include/_G_config.h" 2 3 4
    177 
    178 typedef struct
    179 {
    180   __off_t __pos;
    181   __mbstate_t __state;
    182 } _G_fpos_t;
    183 typedef struct
    184 {
    185   __off64_t __pos;
    186   __mbstate_t __state;
    187 } _G_fpos64_t;
    188 # 53 "/usr/include/_G_config.h" 3 4
    189 typedef int _G_int16_t __attribute__ ((__mode__ (__HI__)));
    190 typedef int _G_int32_t __attribute__ ((__mode__ (__SI__)));
    191 typedef unsigned int _G_uint16_t __attribute__ ((__mode__ (__HI__)));
    192 typedef unsigned int _G_uint32_t __attribute__ ((__mode__ (__SI__)));
    193 # 33 "/usr/include/libio.h" 2 3 4
    194 # 53 "/usr/include/libio.h" 3 4
    195 # 1 "/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stdarg.h" 1 3 4
    196 # 40 "/usr/lib/gcc/x86_64-linux-gnu/4.6/include/stdarg.h" 3 4
    197 typedef __builtin_va_list __gnuc_va_list;
    198 # 54 "/usr/include/libio.h" 2 3 4
    199 # 172 "/usr/include/libio.h" 3 4
    200 struct _IO_jump_t; struct _IO_FILE;
    201 # 182 "/usr/include/libio.h" 3 4
    202 typedef void _IO_lock_t;
    203 
    204 
    205 
    206 
    207 
    208 struct _IO_marker {
    209   struct _IO_marker *_next;
    210   struct _IO_FILE *_sbuf;
    211 
    212 
    213 
    214   int _pos;
    215 # 205 "/usr/include/libio.h" 3 4
    216 };
    217 
    218 
    219 enum __codecvt_result
    220 {
    221   __codecvt_ok,
    222   __codecvt_partial,
    223   __codecvt_error,
    224   __codecvt_noconv
    225 };
    226 # 273 "/usr/include/libio.h" 3 4
    227 struct _IO_FILE {
    228   int _flags;
    229 
    230 
    231 
    232 
    233   char* _IO_read_ptr;
    234   char* _IO_read_end;
    235   char* _IO_read_base;
    236   char* _IO_write_base;
    237   char* _IO_write_ptr;
    238   char* _IO_write_end;
    239   char* _IO_buf_base;
    240   char* _IO_buf_end;
    241 
    242   char *_IO_save_base;
    243   char *_IO_backup_base;
    244   char *_IO_save_end;
    245 
    246   struct _IO_marker *_markers;
    247 
    248   struct _IO_FILE *_chain;
    249 
    250   int _fileno;
    251 
    252 
    253 
    254   int _flags2;
    255 
    256   __off_t _old_offset;
    257 
    258 
    259 
    260   unsigned short _cur_column;
    261   signed char _vtable_offset;
    262   char _shortbuf[1];
    263 
    264 
    265 
    266   _IO_lock_t *_lock;
    267 # 321 "/usr/include/libio.h" 3 4
    268   __off64_t _offset;
    269 # 330 "/usr/include/libio.h" 3 4
    270   void *__pad1;
    271   void *__pad2;
    272   void *__pad3;
    273   void *__pad4;
    274   size_t __pad5;
    275 
    276   int _mode;
    277 
    278   char _unused2[15 * sizeof (int) - 4 * sizeof (void *) - sizeof (size_t)];
    279 
    280 };
    281 
    282 
    283 typedef struct _IO_FILE _IO_FILE;
    284 
    285 
    286 struct _IO_FILE_plus;
    287 
    288 extern struct _IO_FILE_plus _IO_2_1_stdin_;
    289 extern struct _IO_FILE_plus _IO_2_1_stdout_;
    290 extern struct _IO_FILE_plus _IO_2_1_stderr_;
    291 # 366 "/usr/include/libio.h" 3 4
    292 typedef __ssize_t __io_read_fn (void *__cookie, char *__buf, size_t __nbytes);
    293 
    294 
    295 
    296 
    297 
    298 
    299 
    300 typedef __ssize_t __io_write_fn (void *__cookie, __const char *__buf,
    301      size_t __n);
    302 
    303 
    304 
    305 
    306 
    307 
    308 
    309 typedef int __io_seek_fn (void *__cookie, __off64_t *__pos, int __w);
    310 
    311 
    312 typedef int __io_close_fn (void *__cookie);
    313 # 418 "/usr/include/libio.h" 3 4
    314 extern int __underflow (_IO_FILE *);
    315 extern int __uflow (_IO_FILE *);
    316 extern int __overflow (_IO_FILE *, int);
    317 # 462 "/usr/include/libio.h" 3 4
    318 extern int _IO_getc (_IO_FILE *__fp);
    319 extern int _IO_putc (int __c, _IO_FILE *__fp);
    320 extern int _IO_feof (_IO_FILE *__fp) __attribute__ ((__nothrow__ , __leaf__));
    321 extern int _IO_ferror (_IO_FILE *__fp) __attribute__ ((__nothrow__ , __leaf__));
    322 
    323 extern int _IO_peekc_locked (_IO_FILE *__fp);
    324 
    325 
    326 
    327 
    328 
    329 extern void _IO_flockfile (_IO_FILE *) __attribute__ ((__nothrow__ , __leaf__));
    330 extern void _IO_funlockfile (_IO_FILE *) __attribute__ ((__nothrow__ , __leaf__));
    331 extern int _IO_ftrylockfile (_IO_FILE *) __attribute__ ((__nothrow__ , __leaf__));
    332 # 492 "/usr/include/libio.h" 3 4
    333 extern int _IO_vfscanf (_IO_FILE * __restrict, const char * __restrict,
    334    __gnuc_va_list, int *__restrict);
    335 extern int _IO_vfprintf (_IO_FILE *__restrict, const char *__restrict,
    336     __gnuc_va_list);
    337 extern __ssize_t _IO_padn (_IO_FILE *, int, __ssize_t);
    338 extern size_t _IO_sgetn (_IO_FILE *, void *, size_t);
    339 
    340 extern __off64_t _IO_seekoff (_IO_FILE *, __off64_t, int, int);
    341 extern __off64_t _IO_seekpos (_IO_FILE *, __off64_t, int);
    342 
    343 extern void _IO_free_backup_area (_IO_FILE *) __attribute__ ((__nothrow__ , __leaf__));
    344 # 76 "/usr/include/stdio.h" 2 3 4
    345 
    346 
    347 
    348 
    349 typedef __gnuc_va_list va_list;
    350 # 91 "/usr/include/stdio.h" 3 4
    351 typedef __off_t off_t;
    352 # 103 "/usr/include/stdio.h" 3 4
    353 typedef __ssize_t ssize_t;
    354 
    355 
    356 
    357 
    358 
    359 
    360 
    361 typedef _G_fpos_t fpos_t;
    362 
    363 
    364 
    365 
    366 # 165 "/usr/include/stdio.h" 3 4
    367 # 1 "/usr/include/x86_64-linux-gnu/bits/stdio_lim.h" 1 3 4
    368 # 166 "/usr/include/stdio.h" 2 3 4
    369 
    370 
    371 
    372 extern struct _IO_FILE *stdin;
    373 extern struct _IO_FILE *stdout;
    374 extern struct _IO_FILE *stderr;
    375 
    376 
    377 
    378 
    379 
    380 
    381 
    382 extern int remove (__const char *__filename) __attribute__ ((__nothrow__ , __leaf__));
    383 
    384 extern int rename (__const char *__old, __const char *__new) __attribute__ ((__nothrow__ , __leaf__));
    385 
    386 
    387 
    388 
    389 extern int renameat (int __oldfd, __const char *__old, int __newfd,
    390        __const char *__new) __attribute__ ((__nothrow__ , __leaf__));
    391 
    392 
    393 
    394 
    395 
    396 
    397 
    398 
    399 extern FILE *tmpfile (void) ;
    400 # 210 "/usr/include/stdio.h" 3 4
    401 extern char *tmpnam (char *__s) __attribute__ ((__nothrow__ , __leaf__)) ;
    402 
    403 
    404 
    405 
    406 
    407 extern char *tmpnam_r (char *__s) __attribute__ ((__nothrow__ , __leaf__)) ;
    408 # 228 "/usr/include/stdio.h" 3 4
    409 extern char *tempnam (__const char *__dir, __const char *__pfx)
    410      __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__malloc__)) ;
    411 
    412 
    413 
    414 
    415 
    416 
    417 
    418 
    419 extern int fclose (FILE *__stream);
    420 
    421 
    422 
    423 
    424 extern int fflush (FILE *__stream);
    425 
    426 # 253 "/usr/include/stdio.h" 3 4
    427 extern int fflush_unlocked (FILE *__stream);
    428 # 267 "/usr/include/stdio.h" 3 4
    429 
    430 
    431 
    432 
    433 
    434 
    435 extern FILE *fopen (__const char *__restrict __filename,
    436       __const char *__restrict __modes) ;
    437 
    438 
    439 
    440 
    441 extern FILE *freopen (__const char *__restrict __filename,
    442         __const char *__restrict __modes,
    443         FILE *__restrict __stream) ;
    444 # 296 "/usr/include/stdio.h" 3 4
    445 
    446 # 307 "/usr/include/stdio.h" 3 4
    447 extern FILE *fdopen (int __fd, __const char *__modes) __attribute__ ((__nothrow__ , __leaf__)) ;
    448 # 320 "/usr/include/stdio.h" 3 4
    449 extern FILE *fmemopen (void *__s, size_t __len, __const char *__modes)
    450   __attribute__ ((__nothrow__ , __leaf__)) ;
    451 
    452 
    453 
    454 
    455 extern FILE *open_memstream (char **__bufloc, size_t *__sizeloc) __attribute__ ((__nothrow__ , __leaf__)) ;
    456 
    457 
    458 
    459 
    460 
    461 
    462 extern void setbuf (FILE *__restrict __stream, char *__restrict __buf) __attribute__ ((__nothrow__ , __leaf__));
    463 
    464 
    465 
    466 extern int setvbuf (FILE *__restrict __stream, char *__restrict __buf,
    467       int __modes, size_t __n) __attribute__ ((__nothrow__ , __leaf__));
    468 
    469 
    470 
    471 
    472 
    473 extern void setbuffer (FILE *__restrict __stream, char *__restrict __buf,
    474          size_t __size) __attribute__ ((__nothrow__ , __leaf__));
    475 
    476 
    477 extern void setlinebuf (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__));
    478 
    479 
    480 
    481 
    482 
    483 
    484 
    485 
    486 extern int fprintf (FILE *__restrict __stream,
    487       __const char *__restrict __format, ...);
    488 
    489 
    490 
    491 
    492 extern int printf (__const char *__restrict __format, ...);
    493 
    494 extern int sprintf (char *__restrict __s,
    495       __const char *__restrict __format, ...) __attribute__ ((__nothrow__));
    496 
    497 
    498 
    499 
    500 
    501 extern int vfprintf (FILE *__restrict __s, __const char *__restrict __format,
    502        __gnuc_va_list __arg);
    503 
    504 
    505 
    506 
    507 extern int vprintf (__const char *__restrict __format, __gnuc_va_list __arg);
    508 
    509 extern int vsprintf (char *__restrict __s, __const char *__restrict __format,
    510        __gnuc_va_list __arg) __attribute__ ((__nothrow__));
    511 
    512 
    513 
    514 
    515 
    516 extern int snprintf (char *__restrict __s, size_t __maxlen,
    517        __const char *__restrict __format, ...)
    518      __attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 4)));
    519 
    520 extern int vsnprintf (char *__restrict __s, size_t __maxlen,
    521         __const char *__restrict __format, __gnuc_va_list __arg)
    522      __attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 0)));
    523 
    524 # 418 "/usr/include/stdio.h" 3 4
    525 extern int vdprintf (int __fd, __const char *__restrict __fmt,
    526        __gnuc_va_list __arg)
    527      __attribute__ ((__format__ (__printf__, 2, 0)));
    528 extern int dprintf (int __fd, __const char *__restrict __fmt, ...)
    529      __attribute__ ((__format__ (__printf__, 2, 3)));
    530 
    531 
    532 
    533 
    534 
    535 
    536 
    537 
    538 extern int fscanf (FILE *__restrict __stream,
    539      __const char *__restrict __format, ...) ;
    540 
    541 
    542 
    543 
    544 extern int scanf (__const char *__restrict __format, ...) ;
    545 
    546 extern int sscanf (__const char *__restrict __s,
    547      __const char *__restrict __format, ...) __attribute__ ((__nothrow__ , __leaf__));
    548 # 449 "/usr/include/stdio.h" 3 4
    549 extern int fscanf (FILE *__restrict __stream, __const char *__restrict __format, ...) __asm__ ("" "__isoc99_fscanf")
    550 
    551                                ;
    552 extern int scanf (__const char *__restrict __format, ...) __asm__ ("" "__isoc99_scanf")
    553                               ;
    554 extern int sscanf (__const char *__restrict __s, __const char *__restrict __format, ...) __asm__ ("" "__isoc99_sscanf") __attribute__ ((__nothrow__ , __leaf__))
    555 
    556                       ;
    557 # 469 "/usr/include/stdio.h" 3 4
    558 
    559 
    560 
    561 
    562 
    563 
    564 
    565 
    566 extern int vfscanf (FILE *__restrict __s, __const char *__restrict __format,
    567       __gnuc_va_list __arg)
    568      __attribute__ ((__format__ (__scanf__, 2, 0))) ;
    569 
    570 
    571 
    572 
    573 
    574 extern int vscanf (__const char *__restrict __format, __gnuc_va_list __arg)
    575      __attribute__ ((__format__ (__scanf__, 1, 0))) ;
    576 
    577 
    578 extern int vsscanf (__const char *__restrict __s,
    579       __const char *__restrict __format, __gnuc_va_list __arg)
    580      __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__format__ (__scanf__, 2, 0)));
    581 # 500 "/usr/include/stdio.h" 3 4
    582 extern int vfscanf (FILE *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vfscanf")
    583 
    584 
    585 
    586      __attribute__ ((__format__ (__scanf__, 2, 0))) ;
    587 extern int vscanf (__const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vscanf")
    588 
    589      __attribute__ ((__format__ (__scanf__, 1, 0))) ;
    590 extern int vsscanf (__const char *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vsscanf") __attribute__ ((__nothrow__ , __leaf__))
    591 
    592 
    593 
    594      __attribute__ ((__format__ (__scanf__, 2, 0)));
    595 # 528 "/usr/include/stdio.h" 3 4
    596 
    597 
    598 
    599 
    600 
    601 
    602 
    603 
    604 
    605 extern int fgetc (FILE *__stream);
    606 extern int getc (FILE *__stream);
    607 
    608 
    609 
    610 
    611 
    612 extern int getchar (void);
    613 
    614 # 556 "/usr/include/stdio.h" 3 4
    615 extern int getc_unlocked (FILE *__stream);
    616 extern int getchar_unlocked (void);
    617 # 567 "/usr/include/stdio.h" 3 4
    618 extern int fgetc_unlocked (FILE *__stream);
    619 
    620 
    621 
    622 
    623 
    624 
    625 
    626 
    627 
    628 
    629 
    630 extern int fputc (int __c, FILE *__stream);
    631 extern int putc (int __c, FILE *__stream);
    632 
    633 
    634 
    635 
    636 
    637 extern int putchar (int __c);
    638 
    639 # 600 "/usr/include/stdio.h" 3 4
    640 extern int fputc_unlocked (int __c, FILE *__stream);
    641 
    642 
    643 
    644 
    645 
    646 
    647 
    648 extern int putc_unlocked (int __c, FILE *__stream);
    649 extern int putchar_unlocked (int __c);
    650 
    651 
    652 
    653 
    654 
    655 
    656 extern int getw (FILE *__stream);
    657 
    658 
    659 extern int putw (int __w, FILE *__stream);
    660 
    661 
    662 
    663 
    664 
    665 
    666 
    667 
    668 extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream)
    669      ;
    670 
    671 
    672 
    673 
    674 
    675 
    676 extern char *gets (char *__s) ;
    677 
    678 # 662 "/usr/include/stdio.h" 3 4
    679 extern __ssize_t __getdelim (char **__restrict __lineptr,
    680           size_t *__restrict __n, int __delimiter,
    681           FILE *__restrict __stream) ;
    682 extern __ssize_t getdelim (char **__restrict __lineptr,
    683         size_t *__restrict __n, int __delimiter,
    684         FILE *__restrict __stream) ;
    685 
    686 
    687 
    688 
    689 
    690 
    691 
    692 extern __ssize_t getline (char **__restrict __lineptr,
    693        size_t *__restrict __n,
    694        FILE *__restrict __stream) ;
    695 
    696 
    697 
    698 
    699 
    700 
    701 
    702 
    703 extern int fputs (__const char *__restrict __s, FILE *__restrict __stream);
    704 
    705 
    706 
    707 
    708 
    709 extern int puts (__const char *__s);
    710 
    711 
    712 
    713 
    714 
    715 
    716 extern int ungetc (int __c, FILE *__stream);
    717 
    718 
    719 
    720 
    721 
    722 
    723 extern size_t fread (void *__restrict __ptr, size_t __size,
    724        size_t __n, FILE *__restrict __stream) ;
    725 
    726 
    727 
    728 
    729 extern size_t fwrite (__const void *__restrict __ptr, size_t __size,
    730         size_t __n, FILE *__restrict __s);
    731 
    732 # 734 "/usr/include/stdio.h" 3 4
    733 extern size_t fread_unlocked (void *__restrict __ptr, size_t __size,
    734          size_t __n, FILE *__restrict __stream) ;
    735 extern size_t fwrite_unlocked (__const void *__restrict __ptr, size_t __size,
    736           size_t __n, FILE *__restrict __stream);
    737 
    738 
    739 
    740 
    741 
    742 
    743 
    744 
    745 extern int fseek (FILE *__stream, long int __off, int __whence);
    746 
    747 
    748 
    749 
    750 extern long int ftell (FILE *__stream) ;
    751 
    752 
    753 
    754 
    755 extern void rewind (FILE *__stream);
    756 
    757 # 770 "/usr/include/stdio.h" 3 4
    758 extern int fseeko (FILE *__stream, __off_t __off, int __whence);
    759 
    760 
    761 
    762 
    763 extern __off_t ftello (FILE *__stream) ;
    764 # 789 "/usr/include/stdio.h" 3 4
    765 
    766 
    767 
    768 
    769 
    770 
    771 extern int fgetpos (FILE *__restrict __stream, fpos_t *__restrict __pos);
    772 
    773 
    774 
    775 
    776 extern int fsetpos (FILE *__stream, __const fpos_t *__pos);
    777 # 812 "/usr/include/stdio.h" 3 4
    778 
    779 # 821 "/usr/include/stdio.h" 3 4
    780 
    781 
    782 extern void clearerr (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__));
    783 
    784 extern int feof (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ;
    785 
    786 extern int ferror (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ;
    787 
    788 
    789 
    790 
    791 extern void clearerr_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__));
    792 extern int feof_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ;
    793 extern int ferror_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ;
    794 
    795 
    796 
    797 
    798 
    799 
    800 
    801 
    802 extern void perror (__const char *__s);
    803 
    804 
    805 
    806 
    807 
    808 
    809 # 1 "/usr/include/x86_64-linux-gnu/bits/sys_errlist.h" 1 3 4
    810 # 27 "/usr/include/x86_64-linux-gnu/bits/sys_errlist.h" 3 4
    811 extern int sys_nerr;
    812 extern __const char *__const sys_errlist[];
    813 # 851 "/usr/include/stdio.h" 2 3 4
    814 
    815 
    816 
    817 
    818 extern int fileno (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ;
    819 
    820 
    821 
    822 
    823 extern int fileno_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ;
    824 # 870 "/usr/include/stdio.h" 3 4
    825 extern FILE *popen (__const char *__command, __const char *__modes) ;
    826 
    827 
    828 
    829 
    830 
    831 extern int pclose (FILE *__stream);
    832 
    833 
    834 
    835 
    836 
    837 extern char *ctermid (char *__s) __attribute__ ((__nothrow__ , __leaf__));
    838 # 910 "/usr/include/stdio.h" 3 4
    839 extern void flockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__));
    840 
    841 
    842 
    843 extern int ftrylockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ;
    844 
    845 
    846 extern void funlockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__));
    847 # 940 "/usr/include/stdio.h" 3 4
    848 
    849 # 2 "hello.c" 2
    850 
    851 int main()
    852 {
    853  printf("hello world!
    ");
    854 }
    hello.i

      编译阶段。编译器(ccl)将文本文件hello.i翻译成文本文件hello.s,它包含一个汇编语言程序。汇编语言程序中的每条语句都以一种标准的文本格式确切地描述了一条低级机器语言指令。汇编语言是非常有用的,因为他为不同高级语言的不同编译器提供了通用的输出语言。例如,C编译器和Fortran编译器产生的输出文件用的都是一样的汇编语言。

      编译过程就是把预处理完的文件进行一系列的词法分析,语法分析,语义分析及优化后生成相应的汇编代码。

      gcc –S hello.i –o hello.s

     1     .file    "hello.c"
     2     .section    .rodata
     3 .LC0:
     4     .string    "hello world!"
     5     .text
     6     .globl    main
     7     .type    main, @function
     8 main:
     9 .LFB0:
    10     .cfi_startproc
    11     pushq    %rbp
    12     .cfi_def_cfa_offset 16
    13     .cfi_offset 6, -16
    14     movq    %rsp, %rbp
    15     .cfi_def_cfa_register 6
    16     movl    $.LC0, %edi
    17     call    puts
    18     popq    %rbp
    19     .cfi_def_cfa 7, 8
    20     ret
    21     .cfi_endproc
    22 .LFE0:
    23     .size    main, .-main
    24     .ident    "GCC: (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3"
    25     .section    .note.GNU-stack,"",@progbits
    hello.s

      汇编阶段。汇编器(as)将hello.s翻译成机器语言指令,并把这些指令打包成一种叫做可充定位目标程序(relocatable object program)的格式,并将结果保存在目标文件hello.o中,hello.o文件是一个二进制文件,它的字节编码是机器语言指令而不是字符。如果我们在文本编辑器中打开hello.o文件,看到的将是一堆乱码。

      汇编器是将汇编代码转变成机器可以执行的命令,每一个汇编语句几乎都对应一条机器指令。汇编相对于编译过程比较简单,根据汇编指令和机器指令的对照表一一翻译即可。

      $ gcc –c hello.c –o hello.o

      或者

      $ as hello.s –o hello.co

      由于hello.o的内容为机器码,不能以普通文本形式的查看

      连接阶段。请注意,hello程序调用了printf函数,他是每个C编译器都会提供的标准C库中的一个函数。printf函数存在于一个名为printf.o程序中。链接器(ld)就负责处理这种合并。结果就得到hello文件,他是一个可执行目标文件(或者简称可执行文件),可以被加载到内存,由系统执行。

      通过调用链接器ld来链接程序运行需要的一大堆目标文件,以及所依赖的其它库文件,最后生成可执行文件。

      

      参考:

      书籍:《深入理解计算机系统》

      博客:http://blog.csdn.net/koudaidai/article/details/8092647

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  • 原文地址:https://www.cnblogs.com/yunsicai/p/3732816.html
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