gcc编译的过程
Posted coherent3c
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今天再次看了一下Linux下gcc编译的内部工作原理，决定写个博客加深一下自己的印象，如有错误欢迎大家指正。参考书籍《linux c与c++一线开发实践》。
gcc对c/c++语言的编译过程分为四个阶段：预处理、编译、汇编、链接。
1,预处理：是对源程序中的伪指令、特殊符号进行处理的过程。（展开所有宏定义、处理条件编译命令和预编译指令、删除注释等）
首先编写一个代码，保存文件为test.c
1 #include<stdio.h> 2 3 int main(int argc,char **argv[]) 4 { 5 char sz[] = "Hello world! "; 6 printf("%s",sz); 7 fflush(stdout); 8 9 return 0; 10 11 }
其中函数fflush(stdout)的功能为：将缓冲区的内容输出到屏幕上。
-E对test.c文件进行预处理命令，并保存为test.i文件,如下：
gcc -E test.c -o test.i
使用cat -n test.i命令查看test.i所包含的内容(其中-n是为了显示行号)
1 # 1 "test.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 "test.c" 8 # 12 "test.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 # 450 "/usr/include/features.h" 3 4 15 # 1 "/usr/include/sys/cdefs.h" 1 3 4 16 # 460 "/usr/include/sys/cdefs.h" 3 4 17 # 1 "/usr/include/bits/wordsize.h" 1 3 4 18 # 461 "/usr/include/sys/cdefs.h" 2 3 4 19 # 1 "/usr/include/bits/long-double.h" 1 3 4 20 # 462 "/usr/include/sys/cdefs.h" 2 3 4 21 # 451 "/usr/include/features.h" 2 3 4 22 # 474 "/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 # 475 "/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/9.2.0/include/stddef.h" 1 3 4 36 # 209 "/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/stddef.h" 3 4 37 38 # 209 "/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/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/9.2.0/include/stdarg.h" 1 3 4 44 # 40 "/usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/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; 124 125 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__)); 464 465 466 467 468 469 470 extern int fscanf (FILE *__restrict __stream, const char *__restrict __format, ...) __asm__ ("" "__isoc99_fscanf") 471 472 ; 473 extern int scanf (const char *__restrict __format, ...) __asm__ ("" "__isoc99_scanf") 474 ; 475 extern int sscanf (const char *__restrict __s, const char *__restrict __format, ...) __asm__ ("" "__isoc99_sscanf") __attribute__ ((__nothrow__ , __leaf__)) 476 477 ; 478 # 432 "/usr/include/stdio.h" 3 4 479 extern int vfscanf (FILE *__restrict __s, const char *__restrict __format, 480 __gnuc_va_list __arg) 481 __attribute__ ((__format__ (__scanf__, 2, 0))) ; 482 483 484 485 486 487 extern int vscanf (const char *__restrict __format, __gnuc_va_list __arg) 488 __attribute__ ((__format__ (__scanf__, 1, 0))) ; 489 490 491 extern int vsscanf (const char *__restrict __s, 492 const char *__restrict __format, __gnuc_va_list __arg) 493 __attribute__ ((__nothrow__ , __leaf__)) __attribute__ ((__format__ (__scanf__, 2, 0))); 494 495 496 497 498 extern int vfscanf (FILE *__restrict __s, const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vfscanf") 499 500 501 502 __attribute__ ((__format__ (__scanf__, 2, 0))) ; 503 extern int vscanf (const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vscanf") 504 505 __attribute__ ((__format__ (__scanf__, 1, 0))) ; 506 extern int vsscanf (const char *__restrict __s, const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vsscanf") __attribute__ ((__nothrow__ , __leaf__)) 507 508 509 510 __attribute__ ((__format__ (__scanf__, 2, 0))); 511 # 485 "/usr/include/stdio.h" 3 4 512 extern int fgetc (FILE *__stream); 513 extern int getc (FILE *__stream); 514 515 516 517 518 519 extern int getchar (void); 520 521 522 523 524 525 526 extern int getc_unlocked (FILE *__stream); 527 extern int getchar_unlocked (void); 528 # 510 "/usr/include/stdio.h" 3 4 529 extern int fgetc_unlocked (FILE *__stream); 530 # 521 "/usr/include/stdio.h" 3 4 531 extern int fputc (int __c, FILE *__stream); 532 extern int putc (int __c, FILE *__stream); 533 534 535 536 537 538 extern int putchar (int __c); 539 # 537 "/usr/include/stdio.h" 3 4 540 extern int fputc_unlocked (int __c, FILE *__stream); 541 542 543 544 545 546 547 548 extern int putc_unlocked (int __c, FILE *__stream); 549 extern int putchar_unlocked (int __c); 550 551 552 553 554 555 556 extern int getw (FILE *__stream); 557 558 559 extern int putw (int __w, FILE *__stream); 560 561 562 563 564 565 566 567 extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream) 568 ; 569 # 603 "/usr/include/stdio.h" 3 4 570 extern __ssize_t __getdelim (char **__restrict __lineptr, 571 size_t *__restrict __n, int __delimiter, 572 FILE *__restrict __stream) ; 573 extern __ssize_t getdelim (char **__restrict __lineptr, 574 size_t *__restrict __n, int __delimiter, 575 FILE *__restrict __stream) ; 576 577 578 579 580 581 582 583 extern __ssize_t getline (char **__restrict __lineptr, 584 size_t *__restrict __n, 585 FILE *__restrict __stream) ; 586 587 588 589 590 591 592 593 extern int fputs (const char *__restrict __s, FILE *__restrict __stream); 594 595 596 597 598 599 extern int puts (const char *__s); 600 601 602 603 604 605 606 extern int ungetc (int __c, FILE *__stream); 607 608 609 610 611 612 613 extern size_t fread (void *__restrict __ptr, size_t __size, 614 size_t __n, FILE *__restrict __stream) ; 615 616 617 618 619 extern size_t fwrite (const void *__restrict __ptr, size_t __size, 620 size_t __n, FILE *__restrict __s); 621 # 673 "/usr/include/stdio.h" 3 4 622 extern size_t fread_unlocked (void *__restrict __ptr, size_t __size, 623 size_t __n, FILE *__restrict __stream) ; 624 extern size_t fwrite_unlocked (const void *__restrict __ptr, size_t __size, 625 size_t __n, FILE *__restrict __stream); 626 627 628 629 630 631 632 633 extern int fseek (FILE *__stream, long int __off, int __whence); 634 635 636 637 638 extern long int ftell (FILE *__stream) ; 639 640 641 642 643 extern void rewind (FILE *__stream); 644 # 707 "/usr/include/stdio.h" 3 4 645 extern int fseeko (FILE *__stream, __off_t __off, int __whence); 646 647 648 649 650 extern __off_t ftello (FILE *__stream) ; 651 # 731 "/usr/include/stdio.h" 3 4 652 extern int fgetpos (FILE *__restrict __stream, fpos_t *__restrict __pos); 653 654 655 656 657 extern int fsetpos (FILE *__stream, const fpos_t *__pos); 658 # 757 "/usr/include/stdio.h" 3 4 659 extern void clearerr (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 660 661 extern int feof (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 662 663 extern int ferror (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 664 665 666 667 extern void clearerr_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 668 extern int feof_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 669 extern int ferror_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 670 671 672 673 674 675 676 677 extern void perror (const char *__s); 678 679 680 681 682 683 # 1 "/usr/include/bits/sys_errlist.h" 1 3 4 684 # 26 "/usr/include/bits/sys_errlist.h" 3 4 685 extern int sys_nerr; 686 extern const char *const sys_errlist[]; 687 # 782 "/usr/include/stdio.h" 2 3 4 688 689 690 691 692 extern int fileno (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 693 694 695 696 697 extern int fileno_unlocked (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 698 # 800 "/usr/include/stdio.h" 3 4 699 extern FILE *popen (const char *__command, const char *__modes) ; 700 701 702 703 704 705 extern int pclose (FILE *__stream); 706 707 708 709 710 711 extern char *ctermid (char *__s) __attribute__ ((__nothrow__ , __leaf__)); 712 # 840 "/usr/include/stdio.h" 3 4 713 extern void flockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 714 715 716 717 extern int ftrylockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)) ; 718 719 720 extern void funlockfile (FILE *__stream) __attribute__ ((__nothrow__ , __leaf__)); 721 # 858 "/usr/include/stdio.h" 3 4 722 extern int __uflow (FILE *); 723 extern int __overflow (FILE *, int); 724 # 873 "/usr/include/stdio.h" 3 4 725 726 # 13 "test.c" 2 727 728 729 # 14 "test.c" 730 int main(int argc,char **argv[]) 731 { 732 char sz[] = "Hello world! "; 733 printf("%s",sz); 734 fflush( 735 # 18 "test.c" 3 4 736 stdout 737 # 18 "test.c" 738 ); 739 740 return 0; 741 742 }
2,编译:生成相应的汇编代码文件
gcc对C生成的汇编文件是.s文件,编译命令为,
gcc -S test.i -o test.s
同样用cat -n test.s命令查看test.s内容
1 .file "test.c" 2 .text 3 .section .rodata 4 .LC0: 5 .string "%s" 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 $48, %rsp 18 movl %edi, -36(%rbp) 19 movq %rsi, -48(%rbp) 20 movq %fs:40, %rax 21 movq %rax, -8(%rbp) 22 xorl %eax, %eax 23 movabsq $8031924123371070792, %rax 24 movq %rax, -22(%rbp) 25 movl $560229490, -14(%rbp) 26 movw $10, -10(%rbp) 27 leaq -22(%rbp), %rax 28 movq %rax, %rsi 29 leaq .LC0(%rip), %rdi 30 movl $0, %eax 31 call printf@PLT 32 movq stdout(%rip), %rax 33 movq %rax, %rdi 34 call fflush@PLT 35 movl $0, %eax 36 movq -8(%rbp), %rdx 37 xorq %fs:40, %rdx 38 je .L3 39 call __stack_chk_fail@PLT 40 .L3: 41 leave 42 .cfi_def_cfa 7, 8 43 ret 44 .cfi_endproc 45 .LFE0: 46 .size main, .-main 47 .ident "GCC: (GNU) 9.2.0" 48 .section .note.GNU-stack,"",@progbits
3,汇编:将汇编代码转变成二进制代码
gcc -c test.s -o test.o
查看二进制代码和其他不同,可以用hexdump来查看
1 0000000 457f 464c 0102 0001 0000 0000 0000 0000 2 0000010 0001 003e 0001 0000 0000 0000 0000 0000 3 0000020 0000 0000 0000 0000 03b8 0000 0000 0000 4 0000030 0000 0000 0040 0000 0000 0040 000d 000c 5 0000040 4855 e589 8348 30ec 7d89 48dc 7589 64d0 6 0000050 8b48 2504 0028 0000 8948 f845 c031 b848 7 0000060 6548 6c6c 206f 6f77 8948 ea45 45c7 72f2 8 0000070 646c 6621 45c7 0af6 4800 458d 48ea c689 9 0000080 8d48 003d 0000 b800 0000 0000 00e8 0000 10 0000090 4800 058b 0000 0000 8948 e8c7 0000 0000 11 00000a0 00b8 0000 4800 558b 64f8 3348 2514 0028 12 00000b0 0000 0574 00e8 0000 c900 25c3 0073 4700 13 00000c0 4343 203a 4728 554e 2029 2e39 2e32 0030 14 00000d0 0014 0000 0000 0000 7a01 0052 7801 0110 15 00000e0 0c1b 0807 0190 0000 001c 0000 001c 0000 16 00000f0 0000 0000 007b 0000 4100 100e 0286 0d43 17 0000100 0206 0c76 0807 0000 0000 0000 0000 0000 18 0000110 0000 0000 0000 0000 0000 0000 0000 0000 19 0000120 0001 0000 0004 fff1 0000 0000 0000 0000 20 0000130 0000 0000 0000 0000 0000 0000 0003 0001 21 0000140 0000 0000 0000 0000 0000 0000 0000 0000 22 0000150 0000 0000 0003 0003 0000 0000 0000 0000 23 0000160 0000 0000 0000 0000 0000 0000 0003 0004 24 0000170 0000 0000 0000 0000 0000 0000 0000 0000 25 0000180 0000 0000 0003 0005 0000 0000 0000 0000 26 0000190 0000 0000 0000 0000 0000 0000 0003 0007 27 00001a0 0000 0000 0000 0000 0000 0000 0000 0000 28 00001b0 0000 0000 0003 0008 0000 0000 0000 0000 29 00001c0 0000 0000 0000 0000 0000 0000 0003 0006 30 00001d0 0000 0000 0000 0000 0000 0000 0000 0000 31 00001e0 0008 0000 0012 0001 0000 0000 0000 0000 32 00001f0 007b 0000 0000 0000 000d 0000 0010 0000 33 0000200 0000 0000 0000 0000 0000 0000 0000 0000 34 0000210 0023 0000 0010 0000 0000 0000 0000 0000 35 0000220 0000 0000 0000 0000 002a 0000 0010 0000 36 0000230 0000 0000 0000 0000 0000 0000 0000 0000 37 0000240 0031 0000 0010 0000 0000 0000 0000 0000 38 0000250 0000 0000 0000 0000 0038 0000 0010 0000 39 0000260 0000 0000 0000 0000 0000 0000 0000 0000 40 0000270 7400 7365 2e74 0063 616d 6e69 5f00 4c47 41 0000280 424f 4c41 4f5f 4646 4553 5f54 4154 4c42 42 0000290 5f45 7000 6972 746e 0066 7473 6f64 7475 43 00002a0 6600 6c66 7375 0068 5f5f 7473 6361 5f6b 44 00002b0 6863 5f6b 6166 6c69 0000 0000 0000 0000 45 00002c0 0043 0000 0000 0000 0002 0000 0005 0000 46 00002d0 fffc ffff ffff ffff 004d 0000 0000 0000 47 00002e0 0004 0000 000b 0000 fffc ffff ffff ffff 48 00002f0 0054 0000 0000 0000 0002 0000 000c 0000 49 0000300 fffc ffff ffff ffff 005c 0000 0000 0000 50 0000310 0004 0000 000d 0000 fffc ffff ffff ffff 51 0000320 0075 0000 0000 0000 0004 0000 000e 0000 52 0000330 fffc ffff ffff ffff 0020 0000 0000 0000 53 0000340 0002 0000 0002 0000 0000 0000 0000 0000 54 0000350 2e00 7973 746d 6261 2e00 7473 7472 6261 55 0000360 2e00 6873 7473 7472 6261 2e00 6572 616c 56 0000370 742e 7865 0074 642e 7461 0061 622e 7373 57 0000380 2e00 6f72 6164 6174 2e00 6f63 6d6d 6e65 58 0000390 0074 6e2e 746f 2e65 4e47 2d55 7473 6361 59 00003a0 006b 722e 6c65 2e61 6865 665f 6172 656d 60 00003b0 0000 0000 0000 0000 0000 0000 0000 0000 61 * 62 00003f0 0000 0000 0000 0000 0020 0000 0001 0000 63 0000400 0006 0000 0000 0000 0000 0000 0000 0000 64 0000410 0040 0000 0000 0000 007b 0000 0000 0000 65 0000420 0000 0000 0000 0000 0001 0000 0000 0000 66 0000430 0000 0000 0000 0000 001b 0000 0004 0000 67 0000440 0040 0000 0000 0000 0000 0000 0000 0000 68 0000450 02c0 0000 0000 0000 0078 0000 0000 0000 69 0000460 000a 0000 0001 0000 0008 0000 0000 0000 70 0000470 0018 0000 0000 0000 0026 0000 0001 0000 71 0000480 0003 0000 0000 0000 0000 0000 0000 0000 72 0000490 00bb 0000 0000 0000 0000 0000 0000 0000 73 00004a0 0000 0000 0000 0000 0001 0000 0000 0000 74 00004b0 0000 0000 0000 0000 002c 0000 0008 0000 75 00004c0 0003 0000 0000 0000 0000 0000 0000 0000 76 00004d0 00bb 0000 0000 0000 0000 0000 0000 0000 77 00004e0 0000 0000 0000 0000 0001 0000 0000 0000 78 00004f0 0000 0000 0000 0000 0031 0000 0001 0000 79 0000500 0002 0000 0000 0000 0000 0000 0000 0000 80 0000510 00bb 0000 0000 0000 0003 0000 0000 0000 81 0000520 0000 0000 0000 0000 0001 0000 0000 0000 82 0000530 0000 0000 0000 0000 0039 0000 0001 0000 83 0000540 0030 0000 0000 0000 0000 0000 0000 0000 84 0000550 00be 0000 0000 0000 0012 0000 0000 0000 85 0000560 0000 0000 0000 0000 0001 0000 0000 0000 86 0000570 0001 0000 0000 0000 0042 0000 0001 0000 87 0000580 0000 0000 0000 0000 0000 0000 0000 0000 88 0000590 00d0 0000 0000 0000 0000 0000 0000 0000 89 00005a0 0000 0000 0000 0000 0001 0000 0000 0000 90 00005b0 0000 0000 0000 0000 0057 0000 0001 0000 91 00005c0 0002 0000 0000 0000 0000 0000 0000 0000 92 00005d0 00d0 0000 0000 0000 0038 0000 0000 0000 93 00005e0 0000 0000 0000 0000 0008 0000 0000 0000 94 00005f0 0000 0000 0000 0000 0052 0000 0004 0000 95 0000600 0040 0000 0000 0000 0000 0000 0000 0000 96 0000610 0338 0000 0000 0000 0018 0000 0000 0000 97 0000620 000a 0000 0008 0000 0008 0000 0000 0000 98 0000630 0018 0000 0000 0000 0001 0000 0002 0000 99 0000640 0000 0000 0000 0000 0000 0000 0000 0000 100 0000650 0108 0000 0000 0000 0168 0000 0000 0000 101 0000660 000b 0000 0009 0000 0008 0000 0000 0000 102 0000670 0018 0000 0000 0000 0009 0000 0003 0000 103 0000680 0000 0000 0000 0000 0000 0000 0000 0000 104 0000690 0270 0000 0000 0000 0049 0000 0000 0000 105 00006a0 0000 0000 0000 0000 0001 0000 0000 0000 106 00006b0 0000 0000 0000 0000 0011 0000 0003 0000 107 00006c0 0000 0000 0000 0000 0000 0000 0000 0000 108 00006d0 0350 0000 0000 0000 0061 0000 0000 0000 109 00006e0 0000 0000 0000 0000 0001 0000 0000 0000 110 00006f0 0000 0000 0000 0000 111 00006f8
4,链接:主要是为了解决多个文件之间符号引用的问题
gcc test.o -o test
链接完成以后生成目标文件test,命令./test运行test文件(如果有多个目标文件的话可以写在一起用空格隔开,gcc test1.o test2.o test3.o -o test)
Hello world!
如此,gcc内部工作的几个阶段就此完成了,当然实际上并没有如此麻烦,只需要gcc test.c -o test就能生成可执行文件
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