一、源码编辑：
使用vim输入以下内容：hello.c
1 #include <stdio.h> 2 3 int main(int argc, char **argv) 4 { 5 printf("Hello world! "); 6 7 return 0; 8 }
使用hexdump工具查看内容，就是ascii内容为：共0x5f个字节
1 ~ � WORKM � studyCode � gnuC � hexdump -C hello.c 2 00000000 23 69 6e 63 6c 75 64 65 20 3c 73 74 64 69 6f 2e |#include <stdio.| 3 00000010 68 3e 0a 0a 69 6e 74 20 6d 61 69 6e 28 69 6e 74 |h>..int main(int| 4 00000020 20 61 72 67 63 2c 20 63 68 61 72 20 2a 2a 61 72 | argc, char **ar| 5 00000030 67 76 29 0a 7b 0a 09 70 72 69 6e 74 66 28 22 48 |gv).{..printf("H| 6 00000040 65 6c 6c 6f 20 77 6f 72 6c 64 21 5c 6e 22 29 3b |ello world! ");| 7 00000050 0a 0a 09 72 65 74 75 72 6e 20 30 3b 0a 7d 0a |...return 0;.}.| 8 0000005f
二、源码的预处理：
gcc -E hello.c结果为：
1 ~ � WORKM � studyCode � gnuC � gcc -E hello.c 2 # 1 "hello.c" 3 # 1 "<built-in>" 4 # 1 "<命令行>" 5 # 31 "<命令行>" 6 # 1 "/usr/include/stdc-predef.h" 1 3 4 7 # 32 "<命令行>" 2 8 # 1 "hello.c" 9 # 1 "/usr/include/stdio.h" 1 3 4 10 # 27 "/usr/include/stdio.h" 3 4 11 # 1 "/usr/include/bits/libc-header-start.h" 1 3 4 12 # 33 "/usr/include/bits/libc-header-start.h" 3 4 13 # 1 "/usr/include/features.h" 1 3 4 14 # 465 "/usr/include/features.h" 3 4 15 # 1 "/usr/include/sys/cdefs.h" 1 3 4 16 # 452 "/usr/include/sys/cdefs.h" 3 4 17 # 1 "/usr/include/bits/wordsize.h" 1 3 4 18 # 453 "/usr/include/sys/cdefs.h" 2 3 4 19 # 1 "/usr/include/bits/long-double.h" 1 3 4 20 # 454 "/usr/include/sys/cdefs.h" 2 3 4 21 # 466 "/usr/include/features.h" 2 3 4 22 # 489 "/usr/include/features.h" 3 4 23 # 1 "/usr/include/gnu/stubs.h" 1 3 4 24 # 10 "/usr/include/gnu/stubs.h" 3 4 25 # 1 "/usr/include/gnu/stubs-64.h" 1 3 4 26 # 11 "/usr/include/gnu/stubs.h" 2 3 4 27 # 490 "/usr/include/features.h" 2 3 4 28 # 34 "/usr/include/bits/libc-header-start.h" 2 3 4 29 # 28 "/usr/include/stdio.h" 2 3 4 30 31 32 33 34 35 # 1 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stddef.h" 1 3 4 36 # 209 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stddef.h" 3 4 37 38 # 209 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stddef.h" 3 4 39 typedef long unsigned int size_t; 40 # 34 "/usr/include/stdio.h" 2 3 4 41 42 43 # 1 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stdarg.h" 1 3 4 44 # 40 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stdarg.h" 3 4 45 typedef __builtin_va_list __gnuc_va_list; 46 # 37 "/usr/include/stdio.h" 2 3 4 47 48 # 1 "/usr/include/bits/types.h" 1 3 4 49 # 27 "/usr/include/bits/types.h" 3 4 50 # 1 "/usr/include/bits/wordsize.h" 1 3 4 51 # 28 "/usr/include/bits/types.h" 2 3 4 52 # 1 "/usr/include/bits/timesize.h" 1 3 4 53 # 29 "/usr/include/bits/types.h" 2 3 4 54 55 56 typedef unsigned char __u_char; 57 typedef unsigned short int __u_short; 58 typedef unsigned int __u_int; 59 typedef unsigned long int __u_long; 60 61 62 typedef signed char __int8_t; 63 typedef unsigned char __uint8_t; 64 typedef signed short int __int16_t; 65 typedef unsigned short int __uint16_t; 66 typedef signed int __int32_t; 67 typedef unsigned int __uint32_t; 68 69 typedef signed long int __int64_t; 70 typedef unsigned long int __uint64_t; 71 72 73 74 75 76 77 typedef __int8_t __int_least8_t; 78 typedef __uint8_t __uint_least8_t; 79 typedef __int16_t __int_least16_t; 80 typedef __uint16_t __uint_least16_t; 81 typedef __int32_t __int_least32_t; 82 typedef __uint32_t __uint_least32_t; 83 typedef __int64_t __int_least64_t; 84 typedef __uint64_t __uint_least64_t; 85 86 87 88 typedef long int __quad_t; 89 typedef unsigned long int __u_quad_t; 90 91 92 93 94 95 96 97 typedef long int __intmax_t; 98 typedef unsigned long int __uintmax_t; 99 # 141 "/usr/include/bits/types.h" 3 4 100 # 1 "/usr/include/bits/typesizes.h" 1 3 4 101 # 142 "/usr/include/bits/types.h" 2 3 4 102 # 1 "/usr/include/bits/time64.h" 1 3 4 103 # 143 "/usr/include/bits/types.h" 2 3 4 104 105 106 typedef unsigned long int __dev_t; 107 typedef unsigned int __uid_t; 108 typedef unsigned int __gid_t; 109 typedef unsigned long int __ino_t; 110 typedef unsigned long int __ino64_t; 111 typedef unsigned int __mode_t; 112 typedef unsigned long int __nlink_t; 113 typedef long int __off_t; 114 typedef long int __off64_t; 115 typedef int __pid_t; 116 typedef struct { int __val[2]; } __fsid_t; 117 typedef long int __clock_t; 118 typedef unsigned long int __rlim_t; 119 typedef unsigned long int __rlim64_t; 120 typedef unsigned int __id_t; 121 typedef long int __time_t; 122 typedef unsigned int __useconds_t; 123 typedef long int __suseconds_t; 124 typedef long int __suseconds64_t; 125 126 typedef int __daddr_t; 127 typedef int __key_t; 128 129 130 typedef int __clockid_t; 131 132 133 typedef void * __timer_t; 134 135 136 typedef long int __blksize_t; 137 138 139 140 141 typedef long int __blkcnt_t; 142 typedef long int __blkcnt64_t; 143 144 145 typedef unsigned long int __fsblkcnt_t; 146 typedef unsigned long int __fsblkcnt64_t; 147 148 149 typedef unsigned long int __fsfilcnt_t; 150 typedef unsigned long int __fsfilcnt64_t; 151 152 153 typedef long int __fsword_t; 154 155 typedef long int __ssize_t; 156 157 158 typedef long int __syscall_slong_t; 159 160 typedef unsigned long int __syscall_ulong_t; 161 162 163 164 typedef __off64_t __loff_t; 165 typedef char *__caddr_t; 166 167 168 typedef long int __intptr_t; 169 170 171 typedef unsigned int __socklen_t; 172 173 174 175 176 typedef int __sig_atomic_t; 177 # 39 "/usr/include/stdio.h" 2 3 4 178 # 1 "/usr/include/bits/types/__fpos_t.h" 1 3 4 179 180 181 182 183 # 1 "/usr/include/bits/types/__mbstate_t.h" 1 3 4 184 # 13 "/usr/include/bits/types/__mbstate_t.h" 3 4 185 typedef struct 186 { 187 int __count; 188 union 189 { 190 unsigned int __wch; 191 char __wchb[4]; 192 } __value; 193 } __mbstate_t; 194 # 6 "/usr/include/bits/types/__fpos_t.h" 2 3 4 195 196 197 198 199 typedef struct _G_fpos_t 200 { 201 __off_t __pos; 202 __mbstate_t __state; 203 } __fpos_t; 204 # 40 "/usr/include/stdio.h" 2 3 4 205 # 1 "/usr/include/bits/types/__fpos64_t.h" 1 3 4 206 # 10 "/usr/include/bits/types/__fpos64_t.h" 3 4 207 typedef struct _G_fpos64_t 208 { 209 __off64_t __pos; 210 __mbstate_t __state; 211 } __fpos64_t; 212 # 41 "/usr/include/stdio.h" 2 3 4 213 # 1 "/usr/include/bits/types/__FILE.h" 1 3 4 214 215 216 217 struct _IO_FILE; 218 typedef struct _IO_FILE __FILE; 219 # 42 "/usr/include/stdio.h" 2 3 4 220 # 1 "/usr/include/bits/types/FILE.h" 1 3 4 221 222 223 224 struct _IO_FILE; 225 226 227 typedef struct _IO_FILE FILE; 228 # 43 "/usr/include/stdio.h" 2 3 4 229 # 1 "/usr/include/bits/types/struct_FILE.h" 1 3 4 230 # 35 "/usr/include/bits/types/struct_FILE.h" 3 4 231 struct _IO_FILE; 232 struct _IO_marker; 233 struct _IO_codecvt; 234 struct _IO_wide_data; 235 236 237 238 239 typedef void _IO_lock_t; 240 241 242 243 244 245 struct _IO_FILE 246 { 247 int _flags; 248 249 250 char *_IO_read_ptr; 251 char *_IO_read_end; 252 char *_IO_read_base; 253 char *_IO_write_base; 254 char *_IO_write_ptr; 255 char *_IO_write_end; 256 char *_IO_buf_base; 257 char *_IO_buf_end; 258 259 260 char *_IO_save_base; 261 char *_IO_backup_base; 262 char *_IO_save_end; 263 264 struct _IO_marker *_markers; 265 266 struct _IO_FILE *_chain; 267 268 int _fileno; 269 int _flags2; 270 __off_t _old_offset; 271 272 273 unsigned short _cur_column; 274 signed char _vtable_offset; 275 char _shortbuf[1]; 276 277 _IO_lock_t *_lock; 278 279 280 281 282 283 284 285 __off64_t _offset; 286 287 struct _IO_codecvt *_codecvt; 288 struct _IO_wide_data *_wide_data; 289 struct _IO_FILE *_freeres_list; 290 void *_freeres_buf; 291 size_t __pad5; 292 int _mode; 293 294 char _unused2[15 * sizeof (int) - 4 * sizeof (void *) - sizeof (size_t)]; 295 }; 296 # 44 "/usr/include/stdio.h" 2 3 4 297 # 52 "/usr/include/stdio.h" 3 4 298 typedef __gnuc_va_list va_list; 299 # 63 "/usr/include/stdio.h" 3 4 300 typedef __off_t off_t; 301 # 77 "/usr/include/stdio.h" 3 4 302 typedef __ssize_t ssize_t; 303 304 305 306 307 308 309 typedef __fpos_t fpos_t; 310 # 133 "/usr/include/stdio.h" 3 4 311 # 1 "/usr/include/bits/stdio_lim.h" 1 3 4 312 # 134 "/usr/include/stdio.h" 2 3 4 313 314 315 316 extern FILE *stdin; 317 extern FILE *stdout; 318 extern FILE *stderr; 319 320 321 322 323 324 325 extern int remove (const char *__filename) __attribute__ ((__nothrow__ , __leaf__)); 326 327 extern int rename (const char *__old, const char *__new) __attribute__ ((__nothrow__ , __leaf__)); 328 329 330 331 extern int renameat (int __oldfd, const char *__old, int __newfd, 332 const char *__new) __attribute__ ((__nothrow__ , __leaf__)); 333 # 173 "/usr/include/stdio.h" 3 4 334 extern FILE *tmpfile (void) ; 335 # 187 "/usr/include/stdio.h" 3 4 336 extern char *tmpnam (char *__s) __attribute__ ((__nothrow__ , __leaf__)) ; 337 338 339 340 341 extern char *tmpnam_r (char *__s) __attribute__ ((__nothrow__ , __leaf__)) ; 342 # 204 "/usr/include/stdio.h" 3 4 343 extern char *tempnam (const char *__dir, const char *__pfx) 344 __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__malloc__)) ; 345 346 347 348 349 350 351 352 extern int fclose (FILE *__stream); 353 354 355 356 357 extern int fflush (FILE *__stream); 358 # 227 "/usr/include/stdio.h" 3 4 359 extern int fflush_unlocked (FILE *__stream); 360 # 246 "/usr/include/stdio.h" 3 4 361 extern FILE *fopen (const char *__restrict __filename, 362 const char *__restrict __modes) ; 363 364 365 366 367 extern FILE *freopen (const char *__restrict __filename, 368 const char *__restrict __modes, 369 FILE *__restrict __stream) ; 370 # 279 "/usr/include/stdio.h" 3 4 371 extern FILE *fdopen (int __fd, const char *__modes) __attribute__ ((__nothrow__ , __leaf__)) ; 372 # 292 "/usr/include/stdio.h" 3 4 373 extern FILE *fmemopen (void *__s, size_t __len, const char *__modes) 374 __attribute__ ((__nothrow__ , __leaf__)) ; 375 376 377 378 379 extern FILE *open_memstream (char **__bufloc, size_t *__sizeloc) __attribute__ ((__nothrow__ , __leaf__)) ; 380 381 382 383 384 385 extern void setbuf (FILE *__restrict __stream, char *__restrict __buf) __attribute__ ((__nothrow__ , __leaf__)); 386 387 388 389 extern int setvbuf (FILE *__restrict __stream, char *__restrict __buf, 390 int __modes, size_t __n) __attribute__ ((__nothrow__ , __leaf__)); 391 392 393 394 395 extern void setbuffer (FILE *__restrict __stream, char *__restrict __buf, 396 size_t __size) __attribute__ ((__nothrow__ , __leaf__)); 397 398 399 extern void setlinebuf (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 400 401 402 403 404 405 406 407 extern int fprintf (FILE *__restrict __stream, 408 const char *__restrict __format, ...); 409 410 411 412 413 extern int printf (const char *__restrict __format, ...); 414 415 extern int sprintf (char *__restrict __s, 416 const char *__restrict __format, ...) __attribute__ ((__nothrow__)); 417 418 419 420 421 422 extern int vfprintf (FILE *__restrict __s, const char *__restrict __format, 423 __gnuc_va_list __arg); 424 425 426 427 428 extern int vprintf (const char *__restrict __format, __gnuc_va_list __arg); 429 430 extern int vsprintf (char *__restrict __s, const char *__restrict __format, 431 __gnuc_va_list __arg) __attribute__ ((__nothrow__)); 432 433 434 435 extern int snprintf (char *__restrict __s, size_t __maxlen, 436 const char *__restrict __format, ...) 437 __attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 4))); 438 439 extern int vsnprintf (char *__restrict __s, size_t __maxlen, 440 const char *__restrict __format, __gnuc_va_list __arg) 441 __attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 0))); 442 # 379 "/usr/include/stdio.h" 3 4 443 extern int vdprintf (int __fd, const char *__restrict __fmt, 444 __gnuc_va_list __arg) 445 __attribute__ ((__format__ (__printf__, 2, 0))); 446 extern int dprintf (int __fd, const char *__restrict __fmt, ...) 447 __attribute__ ((__format__ (__printf__, 2, 3))); 448 449 450 451 452 453 454 455 extern int fscanf (FILE *__restrict __stream, 456 const char *__restrict __format, ...) ; 457 458 459 460 461 extern int scanf (const char *__restrict __format, ...) ; 462 463 extern int sscanf (const char *__restrict __s, 464 const char *__restrict __format, ...) __attribute__ ((__nothrow__ , __leaf__)); 465 466 467 468 469 470 # 1 "/usr/include/bits/floatn.h" 1 3 4 471 # 119 "/usr/include/bits/floatn.h" 3 4 472 # 1 "/usr/include/bits/floatn-common.h" 1 3 4 473 # 24 "/usr/include/bits/floatn-common.h" 3 4 474 # 1 "/usr/include/bits/long-double.h" 1 3 4 475 # 25 "/usr/include/bits/floatn-common.h" 2 3 4 476 # 120 "/usr/include/bits/floatn.h" 2 3 4 477 # 407 "/usr/include/stdio.h" 2 3 4 478 479 480 481 extern int fscanf (FILE *__restrict __stream, const char *__restrict __format, ...) __asm__ ("" "__isoc99_fscanf") 482 483 ; 484 extern int scanf (const char *__restrict __format, ...) __asm__ ("" "__isoc99_scanf") 485 ; 486 extern int sscanf (const char *__restrict __s, const char *__restrict __format, ...) __asm__ ("" "__isoc99_sscanf") __attribute__ ((__nothrow__ , __leaf__)) 487 488 ; 489 # 435 "/usr/include/stdio.h" 3 4 490 extern int vfscanf (FILE *__restrict __s, const char *__restrict __format, 491 __gnuc_va_list __arg) 492 __attribute__ ((__format__ (__scanf__, 2, 0))) ; 493 494 495 496 497 498 extern int vscanf (const char *__restrict __format, __gnuc_va_list __arg) 499 __attribute__ ((__format__ (__scanf__, 1, 0))) ; 500 501 502 extern int vsscanf (const char *__restrict __s, 503 const char *__restrict __format, __gnuc_va_list __arg) 504 __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__format__ (__scanf__, 2, 0))); 505 506 507 508 509 510 extern int vfscanf (FILE *__restrict __s, const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vfscanf") 511 512 513 514 __attribute__ ((__format__ (__scanf__, 2, 0))) ; 515 extern int vscanf (const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vscanf") 516 517 __attribute__ ((__format__ (__scanf__, 1, 0))) ; 518 extern int vsscanf (const char *__restrict __s, const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vsscanf") __attribute__ ((__nothrow__ , __leaf__)) 519 520 521 522 __attribute__ ((__format__ (__scanf__, 2, 0))); 523 # 489 "/usr/include/stdio.h" 3 4 524 extern int fgetc (FILE *__stream); 525 extern int getc (FILE *__stream); 526 527 528 529 530 531 extern int getchar (void); 532 533 534 535 536 537 538 extern int getc_unlocked (FILE *__stream); 539 extern int getchar_unlocked (void); 540 # 514 "/usr/include/stdio.h" 3 4 541 extern int fgetc_unlocked (FILE *__stream); 542 # 525 "/usr/include/stdio.h" 3 4 543 extern int fputc (int __c, FILE *__stream); 544 extern int putc (int __c, FILE *__stream); 545 546 547 548 549 550 extern int putchar (int __c); 551 # 541 "/usr/include/stdio.h" 3 4 552 extern int fputc_unlocked (int __c, FILE *__stream); 553 554 555 556 557 558 559 560 extern int putc_unlocked (int __c, FILE *__stream); 561 extern int putchar_unlocked (int __c); 562 563 564 565 566 567 568 extern int getw (FILE *__stream); 569 570 571 extern int putw (int __w, FILE *__stream); 572 573 574 575 576 577 578 579 extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream) 580 __attribute__ ((__access__ (__write_only__, 1, 2))); 581 # 608 "/usr/include/stdio.h" 3 4 582 extern __ssize_t __getdelim (char **__restrict __lineptr, 583 size_t *__restrict __n, int __delimiter, 584 FILE *__restrict __stream) ; 585 extern __ssize_t getdelim (char **__restrict __lineptr, 586 size_t *__restrict __n, int __delimiter, 587 FILE *__restrict __stream) ; 588 589 590 591 592 593 594 595 extern __ssize_t getline (char **__restrict __lineptr, 596 size_t *__restrict __n, 597 FILE *__restrict __stream) ; 598 599 600 601 602 603 604 605 extern int fputs (const char *__restrict __s, FILE *__restrict __stream); 606 607 608 609 610 611 extern int puts (const char *__s); 612 613 614 615 616 617 618 extern int ungetc (int __c, FILE *__stream); 619 620 621 622 623 624 625 extern size_t fread (void *__restrict __ptr, size_t __size, 626 size_t __n, FILE *__restrict __stream) ; 627 628 629 630 631 extern size_t fwrite (const void *__restrict __ptr, size_t __size, 632 size_t __n, FILE *__restrict __s); 633 # 678 "/usr/include/stdio.h" 3 4 634 extern size_t fread_unlocked (void *__restrict __ptr, size_t __size, 635 size_t __n, FILE *__restrict __stream) ; 636 extern size_t fwrite_unlocked (const void *__restrict __ptr, size_t __size, 637 size_t __n, FILE *__restrict __stream); 638 639 640 641 642 643 644 645 extern int fseek (FILE *__stream, long int __off, int __whence); 646 647 648 649 650 extern long int ftell (FILE *__stream) ; 651 652 653 654 655 extern void rewind (FILE *__stream); 656 # 712 "/usr/include/stdio.h" 3 4 657 extern int fseeko (FILE *__stream, __off_t __off, int __whence); 658 659 660 661 662 extern __off_t ftello (FILE *__stream) ; 663 # 736 "/usr/include/stdio.h" 3 4 664 extern int fgetpos (FILE *__restrict __stream, fpos_t *__restrict __pos); 665 666 667 668 669 extern int fsetpos (FILE *__stream, const fpos_t *__pos); 670 # 762 "/usr/include/stdio.h" 3 4 671 extern void clearerr (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 672 673 extern int feof (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 674 675 extern int ferror (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 676 677 678 679 extern void clearerr_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 680 extern int feof_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 681 extern int ferror_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 682 683 684 685 686 687 688 689 extern void perror (const char *__s); 690 691 692 693 694 extern int fileno (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 695 696 697 698 699 extern int fileno_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 700 # 799 "/usr/include/stdio.h" 3 4 701 extern FILE *popen (const char *__command, const char *__modes) ; 702 703 704 705 706 707 extern int pclose (FILE *__stream); 708 709 710 711 712 713 extern char *ctermid (char *__s) __attribute__ ((__nothrow__ , __leaf__)); 714 # 839 "/usr/include/stdio.h" 3 4 715 extern void flockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 716 717 718 719 extern int ftrylockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 720 721 722 extern void funlockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 723 # 857 "/usr/include/stdio.h" 3 4 724 extern int __uflow (FILE *); 725 extern int __overflow (FILE *, int); 726 # 874 "/usr/include/stdio.h" 3 4 727 728 # 2 "hello.c" 2 729 730 731 # 3 "hello.c" 732 int main(int argc, char **argv) 733 { 734 printf("Hello world! "); 735 736 return 0; 737 }
以上是直接输出到屏幕，也可以gcc -E hello.c -o hello.i，将预处理结果保存到文件hello.i文件，以便于后期查看（虽然并没有多大用途，但万一哪天需要了呢）
含有宏定义和条件编译的代码：直接用gcc -E hello1.c -o hello1.i
1 # 1 "hello1.c" 2 # 1 "<built-in>" 3 # 1 "<命令行>" 4 # 31 "<命令行>" 5 # 1 "/usr/include/stdc-predef.h" 1 3 4 6 # 32 "<命令行>" 2 7 # 1 "hello1.c" 8 # 1 "/usr/include/stdio.h" 1 3 4 9 # 27 "/usr/include/stdio.h" 3 4 10 # 1 "/usr/include/bits/libc-header-start.h" 1 3 4 11 # 33 "/usr/include/bits/libc-header-start.h" 3 4 12 # 1 "/usr/include/features.h" 1 3 4 13 # 465 "/usr/include/features.h" 3 4 14 # 1 "/usr/include/sys/cdefs.h" 1 3 4 15 # 452 "/usr/include/sys/cdefs.h" 3 4 16 # 1 "/usr/include/bits/wordsize.h" 1 3 4 17 # 453 "/usr/include/sys/cdefs.h" 2 3 4 18 # 1 "/usr/include/bits/long-double.h" 1 3 4 19 # 454 "/usr/include/sys/cdefs.h" 2 3 4 20 # 466 "/usr/include/features.h" 2 3 4 21 # 489 "/usr/include/features.h" 3 4 22 # 1 "/usr/include/gnu/stubs.h" 1 3 4 23 # 10 "/usr/include/gnu/stubs.h" 3 4 24 # 1 "/usr/include/gnu/stubs-64.h" 1 3 4 25 # 11 "/usr/include/gnu/stubs.h" 2 3 4 26 # 490 "/usr/include/features.h" 2 3 4 27 # 34 "/usr/include/bits/libc-header-start.h" 2 3 4 28 # 28 "/usr/include/stdio.h" 2 3 4 29 30 31 32 33 34 # 1 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stddef.h" 1 3 4 35 # 209 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stddef.h" 3 4 36 37 # 209 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stddef.h" 3 4 38 typedef long unsigned int size_t; 39 # 34 "/usr/include/stdio.h" 2 3 4 40 41 42 # 1 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stdarg.h" 1 3 4 43 # 40 "/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include/stdarg.h" 3 4 44 typedef __builtin_va_list __gnuc_va_list; 45 # 37 "/usr/include/stdio.h" 2 3 4 46 47 # 1 "/usr/include/bits/types.h" 1 3 4 48 # 27 "/usr/include/bits/types.h" 3 4 49 # 1 "/usr/include/bits/wordsize.h" 1 3 4 50 # 28 "/usr/include/bits/types.h" 2 3 4 51 # 1 "/usr/include/bits/timesize.h" 1 3 4 52 # 29 "/usr/include/bits/types.h" 2 3 4 53 54 55 typedef unsigned char __u_char; 56 typedef unsigned short int __u_short; 57 typedef unsigned int __u_int; 58 typedef unsigned long int __u_long; 59 60 61 typedef signed char __int8_t; 62 typedef unsigned char __uint8_t; 63 typedef signed short int __int16_t; 64 typedef unsigned short int __uint16_t; 65 typedef signed int __int32_t; 66 typedef unsigned int __uint32_t; 67 68 typedef signed long int __int64_t; 69 typedef unsigned long int __uint64_t; 70 71 72 73 74 75 76 typedef __int8_t __int_least8_t; 77 typedef __uint8_t __uint_least8_t; 78 typedef __int16_t __int_least16_t; 79 typedef __uint16_t __uint_least16_t; 80 typedef __int32_t __int_least32_t; 81 typedef __uint32_t __uint_least32_t; 82 typedef __int64_t __int_least64_t; 83 typedef __uint64_t __uint_least64_t; 84 85 86 87 typedef long int __quad_t; 88 typedef unsigned long int __u_quad_t; 89 90 91 92 93 94 95 96 typedef long int __intmax_t; 97 typedef unsigned long int __uintmax_t; 98 # 141 "/usr/include/bits/types.h" 3 4 99 # 1 "/usr/include/bits/typesizes.h" 1 3 4 100 # 142 "/usr/include/bits/types.h" 2 3 4 101 # 1 "/usr/include/bits/time64.h" 1 3 4 102 # 143 "/usr/include/bits/types.h" 2 3 4 103 104 105 typedef unsigned long int __dev_t; 106 typedef unsigned int __uid_t; 107 typedef unsigned int __gid_t; 108 typedef unsigned long int __ino_t; 109 typedef unsigned long int __ino64_t; 110 typedef unsigned int __mode_t; 111 typedef unsigned long int __nlink_t; 112 typedef long int __off_t; 113 typedef long int __off64_t; 114 typedef int __pid_t; 115 typedef struct { int __val[2]; } __fsid_t; 116 typedef long int __clock_t; 117 typedef unsigned long int __rlim_t; 118 typedef unsigned long int __rlim64_t; 119 typedef unsigned int __id_t; 120 typedef long int __time_t; 121 typedef unsigned int __useconds_t; 122 typedef long int __suseconds_t; 123 typedef long int __suseconds64_t; 124 125 typedef int __daddr_t; 126 typedef int __key_t; 127 128 129 typedef int __clockid_t; 130 131 132 typedef void * __timer_t; 133 134 135 typedef long int __blksize_t; 136 137 138 139 140 typedef long int __blkcnt_t; 141 typedef long int __blkcnt64_t; 142 143 144 typedef unsigned long int __fsblkcnt_t; 145 typedef unsigned long int __fsblkcnt64_t; 146 147 148 typedef unsigned long int __fsfilcnt_t; 149 typedef unsigned long int __fsfilcnt64_t; 150 151 152 typedef long int __fsword_t; 153 154 typedef long int __ssize_t; 155 156 157 typedef long int __syscall_slong_t; 158 159 typedef unsigned long int __syscall_ulong_t; 160 161 162 163 typedef __off64_t __loff_t; 164 typedef char *__caddr_t; 165 166 167 typedef long int __intptr_t; 168 169 170 typedef unsigned int __socklen_t; 171 172 173 174 175 typedef int __sig_atomic_t; 176 # 39 "/usr/include/stdio.h" 2 3 4 177 # 1 "/usr/include/bits/types/__fpos_t.h" 1 3 4 178 179 180 181 182 # 1 "/usr/include/bits/types/__mbstate_t.h" 1 3 4 183 # 13 "/usr/include/bits/types/__mbstate_t.h" 3 4 184 typedef struct 185 { 186 int __count; 187 union 188 { 189 unsigned int __wch; 190 char __wchb[4]; 191 } __value; 192 } __mbstate_t; 193 # 6 "/usr/include/bits/types/__fpos_t.h" 2 3 4 194 195 196 197 198 typedef struct _G_fpos_t 199 { 200 __off_t __pos; 201 __mbstate_t __state; 202 } __fpos_t; 203 # 40 "/usr/include/stdio.h" 2 3 4 204 # 1 "/usr/include/bits/types/__fpos64_t.h" 1 3 4 205 # 10 "/usr/include/bits/types/__fpos64_t.h" 3 4 206 typedef struct _G_fpos64_t 207 { 208 __off64_t __pos; 209 __mbstate_t __state; 210 } __fpos64_t; 211 # 41 "/usr/include/stdio.h" 2 3 4 212 # 1 "/usr/include/bits/types/__FILE.h" 1 3 4 213 214 215 216 struct _IO_FILE; 217 typedef struct _IO_FILE __FILE; 218 # 42 "/usr/include/stdio.h" 2 3 4 219 # 1 "/usr/include/bits/types/FILE.h" 1 3 4 220 221 222 223 struct _IO_FILE; 224 225 226 typedef struct _IO_FILE FILE; 227 # 43 "/usr/include/stdio.h" 2 3 4 228 # 1 "/usr/include/bits/types/struct_FILE.h" 1 3 4 229 # 35 "/usr/include/bits/types/struct_FILE.h" 3 4 230 struct _IO_FILE; 231 struct _IO_marker; 232 struct _IO_codecvt; 233 struct _IO_wide_data; 234 235 236 237 238 typedef void _IO_lock_t; 239 240 241 242 243 244 struct _IO_FILE 245 { 246 int _flags; 247 248 249 char *_IO_read_ptr; 250 char *_IO_read_end; 251 char *_IO_read_base; 252 char *_IO_write_base; 253 char *_IO_write_ptr; 254 char *_IO_write_end; 255 char *_IO_buf_base; 256 char *_IO_buf_end; 257 258 259 char *_IO_save_base; 260 char *_IO_backup_base; 261 char *_IO_save_end; 262 263 struct _IO_marker *_markers; 264 265 struct _IO_FILE *_chain; 266 267 int _fileno; 268 int _flags2; 269 __off_t _old_offset; 270 271 272 unsigned short _cur_column; 273 signed char _vtable_offset; 274 char _shortbuf[1]; 275 276 _IO_lock_t *_lock; 277 278 279 280 281 282 283 284 __off64_t _offset; 285 286 struct _IO_codecvt *_codecvt; 287 struct _IO_wide_data *_wide_data; 288 struct _IO_FILE *_freeres_list; 289 void *_freeres_buf; 290 size_t __pad5; 291 int _mode; 292 293 char _unused2[15 * sizeof (int) - 4 * sizeof (void *) - sizeof (size_t)]; 294 }; 295 # 44 "/usr/include/stdio.h" 2 3 4 296 # 52 "/usr/include/stdio.h" 3 4 297 typedef __gnuc_va_list va_list; 298 # 63 "/usr/include/stdio.h" 3 4 299 typedef __off_t off_t; 300 # 77 "/usr/include/stdio.h" 3 4 301 typedef __ssize_t ssize_t; 302 303 304 305 306 307 308 typedef __fpos_t fpos_t; 309 # 133 "/usr/include/stdio.h" 3 4 310 # 1 "/usr/include/bits/stdio_lim.h" 1 3 4 311 # 134 "/usr/include/stdio.h" 2 3 4 312 313 314 315 extern FILE *stdin; 316 extern FILE *stdout; 317 extern FILE *stderr; 318 319 320 321 322 323 324 extern int remove (const char *__filename) __attribute__ ((__nothrow__ , __leaf__)); 325 326 extern int rename (const char *__old, const char *__new) __attribute__ ((__nothrow__ , __leaf__)); 327 328 329 330 extern int renameat (int __oldfd, const char *__old, int __newfd, 331 const char *__new) __attribute__ ((__nothrow__ , __leaf__)); 332 # 173 "/usr/include/stdio.h" 3 4 333 extern FILE *tmpfile (void) ; 334 # 187 "/usr/include/stdio.h" 3 4 335 extern char *tmpnam (char *__s) __attribute__ ((__nothrow__ , __leaf__)) ; 336 337 338 339 340 extern char *tmpnam_r (char *__s) __attribute__ ((__nothrow__ , __leaf__)) ; 341 # 204 "/usr/include/stdio.h" 3 4 342 extern char *tempnam (const char *__dir, const char *__pfx) 343 __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__malloc__)) ; 344 345 346 347 348 349 350 351 extern int fclose (FILE *__stream); 352 353 354 355 356 extern int fflush (FILE *__stream); 357 # 227 "/usr/include/stdio.h" 3 4 358 extern int fflush_unlocked (FILE *__stream); 359 # 246 "/usr/include/stdio.h" 3 4 360 extern FILE *fopen (const char *__restrict __filename, 361 const char *__restrict __modes) ; 362 363 364 365 366 extern FILE *freopen (const char *__restrict __filename, 367 const char *__restrict __modes, 368 FILE *__restrict __stream) ; 369 # 279 "/usr/include/stdio.h" 3 4 370 extern FILE *fdopen (int __fd, const char *__modes) __attribute__ ((__nothrow__ , __leaf__)) ; 371 # 292 "/usr/include/stdio.h" 3 4 372 extern FILE *fmemopen (void *__s, size_t __len, const char *__modes) 373 __attribute__ ((__nothrow__ , __leaf__)) ; 374 375 376 377 378 extern FILE *open_memstream (char **__bufloc, size_t *__sizeloc) __attribute__ ((__nothrow__ , __leaf__)) ; 379 380 381 382 383 384 extern void setbuf (FILE *__restrict __stream, char *__restrict __buf) __attribute__ ((__nothrow__ , __leaf__)); 385 386 387 388 extern int setvbuf (FILE *__restrict __stream, char *__restrict __buf, 389 int __modes, size_t __n) __attribute__ ((__nothrow__ , __leaf__)); 390 391 392 393 394 extern void setbuffer (FILE *__restrict __stream, char *__restrict __buf, 395 size_t __size) __attribute__ ((__nothrow__ , __leaf__)); 396 397 398 extern void setlinebuf (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 399 400 401 402 403 404 405 406 extern int fprintf (FILE *__restrict __stream, 407 const char *__restrict __format, ...); 408 409 410 411 412 extern int printf (const char *__restrict __format, ...); 413 414 extern int sprintf (char *__restrict __s, 415 const char *__restrict __format, ...) __attribute__ ((__nothrow__)); 416 417 418 419 420 421 extern int vfprintf (FILE *__restrict __s, const char *__restrict __format, 422 __gnuc_va_list __arg); 423 424 425 426 427 extern int vprintf (const char *__restrict __format, __gnuc_va_list __arg); 428 429 extern int vsprintf (char *__restrict __s, const char *__restrict __format, 430 __gnuc_va_list __arg) __attribute__ ((__nothrow__)); 431 432 433 434 extern int snprintf (char *__restrict __s, size_t __maxlen, 435 const char *__restrict __format, ...) 436 __attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 4))); 437 438 extern int vsnprintf (char *__restrict __s, size_t __maxlen, 439 const char *__restrict __format, __gnuc_va_list __arg) 440 __attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 0))); 441 # 379 "/usr/include/stdio.h" 3 4 442 extern int vdprintf (int __fd, const char *__restrict __fmt, 443 __gnuc_va_list __arg) 444 __attribute__ ((__format__ (__printf__, 2, 0))); 445 extern int dprintf (int __fd, const char *__restrict __fmt, ...) 446 __attribute__ ((__format__ (__printf__, 2, 3))); 447 448 449 450 451 452 453 454 extern int fscanf (FILE *__restrict __stream, 455 const char *__restrict __format, ...) ; 456 457 458 459 460 extern int scanf (const char *__restrict __format, ...) ; 461 462 extern int sscanf (const char *__restrict __s, 463 const char *__restrict __format, ...) __attribute__ ((__nothrow__ , __leaf__)); 464 465 466 467 468 469 # 1 "/usr/include/bits/floatn.h" 1 3 4 470 # 119 "/usr/include/bits/floatn.h" 3 4 471 # 1 "/usr/include/bits/floatn-common.h" 1 3 4 472 # 24 "/usr/include/bits/floatn-common.h" 3 4 473 # 1 "/usr/include/bits/long-double.h" 1 3 4 474 # 25 "/usr/include/bits/floatn-common.h" 2 3 4 475 # 120 "/usr/include/bits/floatn.h" 2 3 4 476 # 407 "/usr/include/stdio.h" 2 3 4 477 478 479 480 extern int fscanf (FILE *__restrict __stream, const char *__restrict __format, ...) __asm__ ("" "__isoc99_fscanf") 481 482 ; 483 extern int scanf (const char *__restrict __format, ...) __asm__ ("" "__isoc99_scanf") 484 ; 485 extern int sscanf (const char *__restrict __s, const char *__restrict __format, ...) __asm__ ("" "__isoc99_sscanf") __attribute__ ((__nothrow__ , __leaf__)) 486 487 ; 488 # 435 "/usr/include/stdio.h" 3 4 489 extern int vfscanf (FILE *__restrict __s, const char *__restrict __format, 490 __gnuc_va_list __arg) 491 __attribute__ ((__format__ (__scanf__, 2, 0))) ; 492 493 494 495 496 497 extern int vscanf (const char *__restrict __format, __gnuc_va_list __arg) 498 __attribute__ ((__format__ (__scanf__, 1, 0))) ; 499 500 501 extern int vsscanf (const char *__restrict __s, 502 const char *__restrict __format, __gnuc_va_list __arg) 503 __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__format__ (__scanf__, 2, 0))); 504 505 506 507 508 509 extern int vfscanf (FILE *__restrict __s, const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vfscanf") 510 511 512 513 __attribute__ ((__format__ (__scanf__, 2, 0))) ; 514 extern int vscanf (const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vscanf") 515 516 __attribute__ ((__format__ (__scanf__, 1, 0))) ; 517 extern int vsscanf (const char *__restrict __s, const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vsscanf") __attribute__ ((__nothrow__ , __leaf__)) 518 519 520 521 __attribute__ ((__format__ (__scanf__, 2, 0))); 522 # 489 "/usr/include/stdio.h" 3 4 523 extern int fgetc (FILE *__stream); 524 extern int getc (FILE *__stream); 525 526 527 528 529 530 extern int getchar (void); 531 532 533 534 535 536 537 extern int getc_unlocked (FILE *__stream); 538 extern int getchar_unlocked (void); 539 # 514 "/usr/include/stdio.h" 3 4 540 extern int fgetc_unlocked (FILE *__stream); 541 # 525 "/usr/include/stdio.h" 3 4 542 extern int fputc (int __c, FILE *__stream); 543 extern int putc (int __c, FILE *__stream); 544 545 546 547 548 549 extern int putchar (int __c); 550 # 541 "/usr/include/stdio.h" 3 4 551 extern int fputc_unlocked (int __c, FILE *__stream); 552 553 554 555 556 557 558 559 extern int putc_unlocked (int __c, FILE *__stream); 560 extern int putchar_unlocked (int __c); 561 562 563 564 565 566 567 extern int getw (FILE *__stream); 568 569 570 extern int putw (int __w, FILE *__stream); 571 572 573 574 575 576 577 578 extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream) 579 __attribute__ ((__access__ (__write_only__, 1, 2))); 580 # 608 "/usr/include/stdio.h" 3 4 581 extern __ssize_t __getdelim (char **__restrict __lineptr, 582 size_t *__restrict __n, int __delimiter, 583 FILE *__restrict __stream) ; 584 extern __ssize_t getdelim (char **__restrict __lineptr, 585 size_t *__restrict __n, int __delimiter, 586 FILE *__restrict __stream) ; 587 588 589 590 591 592 593 594 extern __ssize_t getline (char **__restrict __lineptr, 595 size_t *__restrict __n, 596 FILE *__restrict __stream) ; 597 598 599 600 601 602 603 604 extern int fputs (const char *__restrict __s, FILE *__restrict __stream); 605 606 607 608 609 610 extern int puts (const char *__s); 611 612 613 614 615 616 617 extern int ungetc (int __c, FILE *__stream); 618 619 620 621 622 623 624 extern size_t fread (void *__restrict __ptr, size_t __size, 625 size_t __n, FILE *__restrict __stream) ; 626 627 628 629 630 extern size_t fwrite (const void *__restrict __ptr, size_t __size, 631 size_t __n, FILE *__restrict __s); 632 # 678 "/usr/include/stdio.h" 3 4 633 extern size_t fread_unlocked (void *__restrict __ptr, size_t __size, 634 size_t __n, FILE *__restrict __stream) ; 635 extern size_t fwrite_unlocked (const void *__restrict __ptr, size_t __size, 636 size_t __n, FILE *__restrict __stream); 637 638 639 640 641 642 643 644 extern int fseek (FILE *__stream, long int __off, int __whence); 645 646 647 648 649 extern long int ftell (FILE *__stream) ; 650 651 652 653 654 extern void rewind (FILE *__stream); 655 # 712 "/usr/include/stdio.h" 3 4 656 extern int fseeko (FILE *__stream, __off_t __off, int __whence); 657 658 659 660 661 extern __off_t ftello (FILE *__stream) ; 662 # 736 "/usr/include/stdio.h" 3 4 663 extern int fgetpos (FILE *__restrict __stream, fpos_t *__restrict __pos); 664 665 666 667 668 extern int fsetpos (FILE *__stream, const fpos_t *__pos); 669 # 762 "/usr/include/stdio.h" 3 4 670 extern void clearerr (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 671 672 extern int feof (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 673 674 extern int ferror (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 675 676 677 678 extern void clearerr_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 679 extern int feof_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 680 extern int ferror_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 681 682 683 684 685 686 687 688 extern void perror (const char *__s); 689 690 691 692 693 extern int fileno (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 694 695 696 697 698 extern int fileno_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 699 # 799 "/usr/include/stdio.h" 3 4 700 extern FILE *popen (const char *__command, const char *__modes) ; 701 702 703 704 705 706 extern int pclose (FILE *__stream); 707 708 709 710 711 712 extern char *ctermid (char *__s) __attribute__ ((__nothrow__ , __leaf__)); 713 # 839 "/usr/include/stdio.h" 3 4 714 extern void flockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 715 716 717 718 extern int ftrylockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 719 720 721 extern void funlockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 722 # 857 "/usr/include/stdio.h" 3 4 723 extern int __uflow (FILE *); 724 extern int __overflow (FILE *, int); 725 # 874 "/usr/include/stdio.h" 3 4 726 727 # 2 "hello1.c" 2 728 729 730 731 732 # 5 "hello1.c" 733 int main(int argc, char **argv) 734 { 735 printf("Hello world! NUM: %d ", 8); 736 737 return 0; 738 }
735行可以明显看出宏定义中的#define NUM 8已经其作用了，NUM已经被替换成功，包含条件编译的代码如下：
1 #include <stdio.h> 2 3 #define NUM 8 4 5 int main(int argc, char **argv) 6 { 7 printf("Hello world! NUM: %d ", NUM); 8 9 #ifdef TEST 10 printf("Test mode ...... "); 11 #endif 12 13 return 0; 14 }
若使用gcc -UTEST -g hello1.c -o hello1T，没有定义宏定义TEST，则结果为：
预编译结果为，其他不太相关部分省略：
# 857 "/usr/include/stdio.h" 3 4 722 extern int __uflow (FILE *); 723 extern int __overflow (FILE *, int); 724 # 874 "/usr/include/stdio.h" 3 4 725 726 # 2 "hello1.c" 2 727 728 729 730 731 # 5 "hello1.c" 732 int main(int argc, char **argv) 733 { 734 printf("Hello world! NUM: %d ", 8); 735 736 737 738 739 740 return 0; 741 }
最终执行结果为：
Hello world! NUM: 8
若使用gcc -DTEST -g hello1.c -o hello1N，定义了宏定义TEST，则结果为：
721 # 857 "/usr/include/stdio.h" 3 4 722 extern int __uflow (FILE *); 723 extern int __overflow (FILE *, int); 724 # 874 "/usr/include/stdio.h" 3 4 725 726 # 2 "hello1.c" 2 727 728 729 730 731 # 5 "hello1.c" 732 int main(int argc, char **argv) 733 { 734 printf("Hello world! NUM: %d ", 8); 735 736 737 printf("Test mode ...... "); 738 739 740 return 0; 741 }
最终执行结果为：
Hello world! NUM: 8
Test mode ......
三、源码的编译：
gcc -S hello.c或 gcc -S （-masam=att） hello.c -o hello.s结果为，是AT&T汇编：
1 .file "hello.c" 2 .text 3 .section .rodata 4 .LC0: 5 .string "Hello world!" 6 .text 7 .globl main 8 .type main, @function 9 main: 10 .LFB0: 11 .cfi_startproc 12 pushq %rbp 13 .cfi_def_cfa_offset 16 14 .cfi_offset 6, -16 15 movq %rsp, %rbp 16 .cfi_def_cfa_register 6 17 subq $16, %rsp 18 movl %edi, -4(%rbp) 19 movq %rsi, -16(%rbp) 20 leaq .LC0(%rip), %rdi 21 call puts@PLT 22 movl $0, %eax 23 leave 24 .cfi_def_cfa 7, 8 25 ret 26 .cfi_endproc 27 .LFE0: 28 .size main, .-main 29 .ident "GCC: (GNU) 10.2.0" 30 .section .note.GNU-stack,"",@progbits
gcc -S -masam=intel hello.c -o hello.s结果为，是INTEL汇编：
1 .file "hello.c" 2 .intel_syntax noprefix 3 .text 4 .section .rodata 5 .LC0: 6 .string "Hello world!" 7 .text 8 .globl main 9 .type main, @function 10 main: 11 .LFB0: 12 .cfi_startproc 13 push rbp 14 .cfi_def_cfa_offset 16 15 .cfi_offset 6, -16 16 mov rbp, rsp 17 .cfi_def_cfa_register 6 18 sub rsp, 16 19 mov DWORD PTR -4[rbp], edi 20 mov QWORD PTR -16[rbp], rsi 21 lea rdi, .LC0[rip] 22 call puts@PLT 23 mov eax, 0 24 leave 25 .cfi_def_cfa 7, 8 26 ret 27 .cfi_endproc 28 .LFE0: 29 .size main, .-main 30 .ident "GCC: (GNU) 10.2.0" 31 .section .note.GNU-stack,"",@progbits
下面讲解以att的代码为例：
说明：第1行：表明文件名为hello.c
第2行：text段开始
第3行：表示节名，只读段没有内容
第4行：只是一个标号，具体不太明白
第5行：用到的字符串"Hello world!"
第6行：代码节，text段开始
第7行：main是全局变量名
第8行：表明main是个函数名
第9行：表示main函数开始
第10行：表示main函数代码的开始，第一个函数的开始；
第11行：cif(call frame infromation)开始，表明有调用函数
第12行：保存栈基址
第13行：偏移出16个字节的空间，cfa（Canonical Frame Address规范化帧地址）
第14行：先前寄存器的值保存在取自CFA的偏移地址中
第15行：将栈顶指针作为新的栈基址
第16行：Canonical Frame Address （规范化帧地址）
第17行：开辟16字节的空间
第18行：将edi数据存入栈帧
第19行：将rsi数据存入栈帧
第20行：计算新地址
第21行：调用函数PLT
第22行：将0放入eax中，准备返回值，0为正常返回
第23行：离开
第24行：改变cfa的偏移地址
第25行：返回
第26行：cif(call frame infromation)结束，
第27行：表示main函数代码的结束，第一个函数的结束
第28行：size信息
第29行：编译器的信息
第30行：段的信息
.cfi_def_cfa register, offset：定义规范化栈地址：将寄存器中的地址进行偏移获取新地址；
.cfi_def_cfa_register register：改变计算规范化地址的规则：从现在开始寄存器用新值替换旧的值，偏移地址保持不变；
.cfi_def_cfa_offset offset：改变计算规范化地址的规则：寄存器不变，改变偏移地址；
改变计算规范化地址的规则：寄存器不变，改变偏移地址；.cfi_adjust_cfa_offset offset：和 .cfi_def_cfa_offset 相同，不同的是偏移地址通过相加或相减先前的偏移地址；
.cfi_offset register, offset：先前寄存器的值保存在取自CFA的偏移地址中；
四、汇编源码的汇编：
gcc -c helloA.s 生成helloA.o文件
可以通过objdump -d helloA.o
1 ~ � WORKM � studyCode � gnuC � objdump -d helloA.o 2 3 helloA.o： 文件格式 elf64-x86-64 4 5 6 Disassembly of section .text: 7 8 0000000000000000 <main>: 9 0: 55 push %rbp 10 1: 48 89 e5 mov %rsp,%rbp 11 4: 48 83 ec 10 sub $0x10,%rsp 12 8: 89 7d fc mov %edi,-0x4(%rbp) 13 b: 48 89 75 f0 mov %rsi,-0x10(%rbp) 14 f: 48 8d 3d 00 00 00 00 lea 0x0(%rip),%rdi # 16 <main+0x16> 15 16: e8 00 00 00 00 callq 1b <main+0x1b> 16 1b: b8 00 00 00 00 mov $0x0,%eax 17 20: c9 leaveq 18 21: c3 retq
gcc helloA.o -o helloA 生成可执行文件
也可以使用objdump -D helloAA >> helloAAA,内容为
1 helloAA： 文件格式 elf64-x86-64 2 3 4 Disassembly of section .init: 5 6 0000000000001000 <_init>: 7 1000: f3 0f 1e fa endbr64 8 1004: 48 83 ec 08 sub $0x8,%rsp 9 1008: 48 8b 05 d9 2f 00 00 mov 0x2fd9(%rip),%rax # 3fe8 <__gmon_start__> 10 100f: 48 85 c0 test %rax,%rax 11 1012: 74 02 je 1016 <_init+0x16> 12 1014: ff d0 callq *%rax 13 1016: 48 83 c4 08 add $0x8,%rsp 14 101a: c3 retq 15 16 Disassembly of section .plt: 17 18 0000000000001020 <.plt>: 19 1020: ff 35 e2 2f 00 00 pushq 0x2fe2(%rip) # 4008 <_GLOBAL_OFFSET_TABLE_+0x8> 20 1026: ff 25 e4 2f 00 00 jmpq *0x2fe4(%rip) # 4010 <_GLOBAL_OFFSET_TABLE_+0x10> 21 102c: 0f 1f 40 00 nopl 0x0(%rax) 22 23 0000000000001030 <puts@plt>: 24 1030: ff 25 e2 2f 00 00 jmpq *0x2fe2(%rip) # 4018 <puts@GLIBC_2.2.5> 25 1036: 68 00 00 00 00 pushq $0x0 26 103b: e9 e0 ff ff ff jmpq 1020 <.plt> 27 28 Disassembly of section .text: 29 30 0000000000001040 <_start>: 31 1040: f3 0f 1e fa endbr64 32 1044: 31 ed xor %ebp,%ebp 33 1046: 49 89 d1 mov %rdx,%r9 34 1049: 5e pop %rsi 35 104a: 48 89 e2 mov %rsp,%rdx 36 104d: 48 83 e4 f0 and $0xfffffffffffffff0,%rsp 37 1051: 50 push %rax 38 1052: 54 push %rsp 39 1053: 4c 8d 05 76 01 00 00 lea 0x176(%rip),%r8 # 11d0 <__libc_csu_fini> 40 105a: 48 8d 0d ff 00 00 00 lea 0xff(%rip),%rcx # 1160 <__libc_csu_init> 41 1061: 48 8d 3d d1 00 00 00 lea 0xd1(%rip),%rdi # 1139 <main> 42 1068: ff 15 72 2f 00 00 callq *0x2f72(%rip) # 3fe0 <__libc_start_main@GLIBC_2.2.5> 43 106e: f4 hlt 44 106f: 90 nop 45 46 0000000000001070 <deregister_tm_clones>: 47 1070: 48 8d 3d b9 2f 00 00 lea 0x2fb9(%rip),%rdi # 4030 <__TMC_END__> 48 1077: 48 8d 05 b2 2f 00 00 lea 0x2fb2(%rip),%rax # 4030 <__TMC_END__> 49 107e: 48 39 f8 cmp %rdi,%rax 50 1081: 74 15 je 1098 <deregister_tm_clones+0x28> 51 1083: 48 8b 05 4e 2f 00 00 mov 0x2f4e(%rip),%rax # 3fd8 <_ITM_deregisterTMCloneTable> 52 108a: 48 85 c0 test %rax,%rax 53 108d: 74 09 je 1098 <deregister_tm_clones+0x28> 54 108f: ff e0 jmpq *%rax 55 1091: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 56 1098: c3 retq 57 1099: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 58 59 00000000000010a0 <register_tm_clones>: 60 10a0: 48 8d 3d 89 2f 00 00 lea 0x2f89(%rip),%rdi # 4030 <__TMC_END__> 61 10a7: 48 8d 35 82 2f 00 00 lea 0x2f82(%rip),%rsi # 4030 <__TMC_END__> 62 10ae: 48 29 fe sub %rdi,%rsi 63 10b1: 48 89 f0 mov %rsi,%rax 64 10b4: 48 c1 ee 3f shr $0x3f,%rsi 65 10b8: 48 c1 f8 03 sar $0x3,%rax 66 10bc: 48 01 c6 add %rax,%rsi 67 10bf: 48 d1 fe sar %rsi 68 10c2: 74 14 je 10d8 <register_tm_clones+0x38> 69 10c4: 48 8b 05 25 2f 00 00 mov 0x2f25(%rip),%rax # 3ff0 <_ITM_registerTMCloneTable> 70 10cb: 48 85 c0 test %rax,%rax 71 10ce: 74 08 je 10d8 <register_tm_clones+0x38> 72 10d0: ff e0 jmpq *%rax 73 10d2: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1) 74 10d8: c3 retq 75 10d9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 76 77 00000000000010e0 <__do_global_dtors_aux>: 78 10e0: f3 0f 1e fa endbr64 79 10e4: 80 3d 45 2f 00 00 00 cmpb $0x0,0x2f45(%rip) # 4030 <__TMC_END__> 80 10eb: 75 33 jne 1120 <__do_global_dtors_aux+0x40> 81 10ed: 55 push %rbp 82 10ee: 48 83 3d 02 2f 00 00 cmpq $0x0,0x2f02(%rip) # 3ff8 <__cxa_finalize@GLIBC_2.2.5> 83 10f5: 00 84 10f6: 48 89 e5 mov %rsp,%rbp 85 10f9: 74 0d je 1108 <__do_global_dtors_aux+0x28> 86 10fb: 48 8b 3d 26 2f 00 00 mov 0x2f26(%rip),%rdi # 4028 <__dso_handle> 87 1102: ff 15 f0 2e 00 00 callq *0x2ef0(%rip) # 3ff8 <__cxa_finalize@GLIBC_2.2.5> 88 1108: e8 63 ff ff ff callq 1070 <deregister_tm_clones> 89 110d: c6 05 1c 2f 00 00 01 movb $0x1,0x2f1c(%rip) # 4030 <__TMC_END__> 90 1114: 5d pop %rbp 91 1115: c3 retq 92 1116: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1) 93 111d: 00 00 00 94 1120: c3 retq 95 1121: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1) 96 1128: 00 00 00 00 97 112c: 0f 1f 40 00 nopl 0x0(%rax) 98 99 0000000000001130 <frame_dummy>: 100 1130: f3 0f 1e fa endbr64 101 1134: e9 67 ff ff ff jmpq 10a0 <register_tm_clones> 102 103 0000000000001139 <main>: 104 1139: 55 push %rbp 105 113a: 48 89 e5 mov %rsp,%rbp 106 113d: 48 83 ec 10 sub $0x10,%rsp 107 1141: 89 7d fc mov %edi,-0x4(%rbp) 108 1144: 48 89 75 f0 mov %rsi,-0x10(%rbp) 109 1148: 48 8d 3d b5 0e 00 00 lea 0xeb5(%rip),%rdi # 2004 <_IO_stdin_used+0x4> 110 114f: e8 dc fe ff ff callq 1030 <puts@plt> 111 1154: b8 00 00 00 00 mov $0x0,%eax 112 1159: c9 leaveq 113 115a: c3 retq 114 115b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 115 116 0000000000001160 <__libc_csu_init>: 117 1160: f3 0f 1e fa endbr64 118 1164: 41 57 push %r15 119 1166: 4c 8d 3d 7b 2c 00 00 lea 0x2c7b(%rip),%r15 # 3de8 <__frame_dummy_init_array_entry> 120 116d: 41 56 push %r14 121 116f: 49 89 d6 mov %rdx,%r14 122 1172: 41 55 push %r13 123 1174: 49 89 f5 mov %rsi,%r13 124 1177: 41 54 push %r12 125 1179: 41 89 fc mov %edi,%r12d 126 117c: 55 push %rbp 127 117d: 48 8d 2d 6c 2c 00 00 lea 0x2c6c(%rip),%rbp # 3df0 <__do_global_dtors_aux_fini_array_entry> 128 1184: 53 push %rbx 129 1185: 4c 29 fd sub %r15,%rbp 130 1188: 48 83 ec 08 sub $0x8,%rsp 131 118c: e8 6f fe ff ff callq 1000 <_init> 132 1191: 48 c1 fd 03 sar $0x3,%rbp 133 1195: 74 1f je 11b6 <__libc_csu_init+0x56> 134 1197: 31 db xor %ebx,%ebx 135 1199: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) 136 11a0: 4c 89 f2 mov %r14,%rdx 137 11a3: 4c 89 ee mov %r13,%rsi 138 11a6: 44 89 e7 mov %r12d,%edi 139 11a9: 41 ff 14 df callq *(%r15,%rbx,8) 140 11ad: 48 83 c3 01 add $0x1,%rbx 141 11b1: 48 39 dd cmp %rbx,%rbp 142 11b4: 75 ea jne 11a0 <__libc_csu_init+0x40> 143 11b6: 48 83 c4 08 add $0x8,%rsp 144 11ba: 5b pop %rbx 145 11bb: 5d pop %rbp 146 11bc: 41 5c pop %r12 147 11be: 41 5d pop %r13 148 11c0: 41 5e pop %r14 149 11c2: 41 5f pop %r15 150 11c4: c3 retq 151 11c5: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1) 152 11cc: 00 00 00 00 153 154 00000000000011d0 <__libc_csu_fini>: 155 11d0: f3 0f 1e fa endbr64 156 11d4: c3 retq 157 158 Disassembly of section .fini: 159 160 00000000000011d8 <_fini>: 161 11d8: f3 0f 1e fa endbr64 162 11dc: 48 83 ec 08 sub $0x8,%rsp 163 11e0: 48 83 c4 08 add $0x8,%rsp 164 11e4: c3 retq ~
五、链接：
经过前面的步骤，可以生成多个目标代码，壳虫定位目标码都是按地址0作为起始地址的，调用其他模块的函数的callq指令中的地址并没有填充被调用代码的地址。链接主要完成两个事情：
（1）、将各个模块目标代码在程序空间中指定自己的不重叠的位置和区间，这个举动常常称为“布局”。
（2）、对未确定的地址将布局后对应的函数地址替换函数调用中的全0地址，这个举动常被称为重定位，调用其他模块上的函数需要重定位，引用其他模块上的变量需要重定位，甚至引用本模块中的全局变量也需要重定位；使用静态链接，程序创建后就可以确定地址；使用动态链接，需要一个辅助位置，在程序运行中才能确定具体地址；
六、编译驱动：
gcc -v -g hello1.c -o hello1
1 ~ � WORKM � studyCode � gnuC � gcc -v -g hello1.c -o hello1 2 使用内建 specs。 3 COLLECT_GCC=gcc 4 COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/lto-wrapper 5 目标：x86_64-pc-linux-gnu 6 配置为：/build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib --libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=https://bugs.archlinux.org/ --enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --with-isl --with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit --enable-cet=auto --enable-checking=release --enable-clocale=gnu --enable-default-pie --enable-default-ssp --enable-gnu-indirect-function --enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id --enable-lto --enable-multilib --enable-plugin --enable-shared --enable-threads=posix --disable-libssp --disable-libstdcxx-pch --disable-libunwind-exceptions --disable-werror gdc_include_dir=/usr/include/dlang/gdc 7 线程模型：posix 8 Supported LTO compression algorithms: zlib zstd 9 gcc 版本 10.2.0 (GCC) 10 COLLECT_GCC_OPTIONS='-v' '-g' '-o' 'hello1' '-mtune=generic' '-march=x86-64' 11 /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/cc1 -quiet -v hello1.c -quiet -dumpbase hello1.c -mtune=generic -march=x86-64 -auxbase hello1 -g -version -o /tmp/cceOgteA.s 12 GNU C17 (GCC) 版本 10.2.0 (x86_64-pc-linux-gnu) 13 由 GNU C 版本 10.2.0 编译，GMP 版本 6.2.0，MPFR 版本 4.1.0，MPC 版本 1.1.0，isl 版本 isl-0.21-GMP 14 15 GGC 准则：--param ggc-min-expand=100 --param ggc-min-heapsize=131072 16 忽略不存在的目录“/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../x86_64-pc-linux-gnu/include” 17 #include "..." 搜索从这里开始： 18 #include <...> 搜索从这里开始： 19 /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include 20 /usr/local/include 21 /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/include-fixed 22 /usr/include 23 搜索列表结束。 24 GNU C17 (GCC) 版本 10.2.0 (x86_64-pc-linux-gnu) 25 由 GNU C 版本 10.2.0 编译，GMP 版本 6.2.0，MPFR 版本 4.1.0，MPC 版本 1.1.0，isl 版本 isl-0.21-GMP 26 27 GGC 准则：--param ggc-min-expand=100 --param ggc-min-heapsize=131072 28 Compiler executable checksum: 81412c83e0c3f5014cd5328f9bc3d624 29 COLLECT_GCC_OPTIONS='-v' '-g' '-o' 'hello1' '-mtune=generic' '-march=x86-64' 30 as -v --64 -o /tmp/cc58cN9y.o /tmp/cceOgteA.s 31 GNU assembler version 2.35.1 (x86_64-pc-linux-gnu) using BFD version (GNU Binutils) 2.35.1 32 COMPILER_PATH=/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/:/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/:/usr/lib/gcc/x86_64-pc-linux-gnu/:/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/:/usr/lib/gcc/x86_64-pc-linux-gnu/ 33 LIBRARY_PATH=/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/:/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../:/lib/:/usr/lib/ 34 COLLECT_GCC_OPTIONS='-v' '-g' '-o' 'hello1' '-mtune=generic' '-march=x86-64' 35 /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/collect2 -plugin /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/liblto_plugin.so -plugin-opt=/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/lto-wrapper -plugin-opt=-fresolution=/tmp/ccaxp9Vy.res -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s -plugin-opt=-pass-through=-lc -plugin-opt=-pass-through=-lgcc -plugin-opt=-pass-through=-lgcc_s --build-id --eh-frame-hdr --hash-style=gnu -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -pie -o hello1 /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../lib/Scrt1.o /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../lib/crti.o /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/crtbeginS.o -L/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0 -L/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../lib -L/lib/../lib -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../.. /tmp/cc58cN9y.o -lgcc --push-state --as-needed -lgcc_s --pop-state -lc -lgcc --push-state --as-needed -lgcc_s --pop-state /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/crtendS.o /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0/../../../../lib/crtn.o 36 COLLECT_GCC_OPTIONS='-v' '-g' '-o' 'hello1' '-mtune=generic' '-march=x86-64'
搞定了。