C程序编译过程
1、C程序编译主要有以下几个步骤：
1、预处理阶段：预处理主要讲定义的宏或者以#开头的指令和特殊符号处理，有宏定义：做替换、包含头文件展开等；
2、编译阶段：经过了上一步骤的预处理后，通常只剩下常量，数字、字符串、变量定义以及C语言关键字；生成了汇编代码；
3、汇编阶段：接着上面生成的汇编代码，在这阶段将该汇编代码生成二进制的文件的机器代码；生成二进制文件；
4、连接阶段： 该阶段主要讲上面生成的目标文件连接起来，在多个文件定义的符号都连接起来生成可执行文件；
2、代码示例：
1、演示C代码（编译环境在Ubuntu下的gcc）
#include<stdio.h> #define pi 3.1415926 void main() { printf("Pi is %f\n",pi); printf("hello world\n"); getchar(); }
2、预处理阶段
gcc -E demo01.c -o demo01.i // 预处理
生成预处理后的代码，使用文本工具打开demo01.i
# 1 "demo01.c" # 1 "<built-in>" # 1 "<command-line>" # 1 "demo01.c" # 1 "/usr/include/stdio.h" 1 3 4 # 28 "/usr/include/stdio.h" 3 4 # 1 "/usr/include/features.h" 1 3 4 # 324 "/usr/include/features.h" 3 4 # 1 "/usr/include/x86_64-linux-gnu/bits/predefs.h" 1 3 4 # 325 "/usr/include/features.h" 2 3 4 # 357 "/usr/include/features.h" 3 4 # 1 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 1 3 4 # 378 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 3 4 # 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4 # 379 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 2 3 4 # 358 "/usr/include/features.h" 2 3 4 # 389 "/usr/include/features.h" 3 4 # 1 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 1 3 4 # 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4 # 5 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 2 3 4 # 1 "/usr/include/x86_64-linux-gnu/gnu/stubs-64.h" 1 3 4 # 10 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 2 3 4 # 390 "/usr/include/features.h" 2 3 4 # 29 "/usr/include/stdio.h" 2 3 4 # 1 "/usr/lib/gcc/x86_64-linux-gnu/4.4.7/include/stddef.h" 1 3 4 # 211 "/usr/lib/gcc/x86_64-linux-gnu/4.4.7/include/stddef.h" 3 4 typedef long unsigned int size_t; # 35 "/usr/include/stdio.h" 2 3 4 # 1 "/usr/include/x86_64-linux-gnu/bits/types.h" 1 3 4 # 28 "/usr/include/x86_64-linux-gnu/bits/types.h" 3 4 # 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4 # 29 "/usr/include/x86_64-linux-gnu/bits/types.h" 2 3 4 typedef unsigned char __u_char; typedef unsigned short int __u_short; typedef unsigned int __u_int; typedef unsigned long int __u_long; typedef signed char __int8_t; typedef unsigned char __uint8_t; typedef signed short int __int16_t; typedef unsigned short int __uint16_t; typedef signed int __int32_t; typedef unsigned int __uint32_t; typedef signed long int __int64_t; typedef unsigned long int __uint64_t; typedef long int __quad_t; typedef unsigned long int __u_quad_t; # 131 "/usr/include/x86_64-linux-gnu/bits/types.h" 3 4 # 1 "/usr/include/x86_64-linux-gnu/bits/typesizes.h" 1 3 4 # 132 "/usr/include/x86_64-linux-gnu/bits/types.h" 2 3 4 typedef unsigned long int __dev_t; typedef unsigned int __uid_t; typedef unsigned int __gid_t; typedef unsigned long int __ino_t; typedef unsigned long int __ino64_t; typedef unsigned int __mode_t; typedef unsigned long int __nlink_t; typedef long int __off_t; typedef long int __off64_t; typedef int __pid_t; typedef struct { int __val[2]; } __fsid_t; typedef long int __clock_t; typedef unsigned long int __rlim_t; typedef unsigned long int __rlim64_t; typedef unsigned int __id_t; typedef long int __time_t; typedef unsigned int __useconds_t; typedef long int __suseconds_t; typedef int __daddr_t; typedef long int __swblk_t; typedef int __key_t; typedef int __clockid_t; typedef void * __timer_t; typedef long int __blksize_t; typedef long int __blkcnt_t; typedef long int __blkcnt64_t; typedef unsigned long int __fsblkcnt_t; typedef unsigned long int __fsblkcnt64_t; typedef unsigned long int __fsfilcnt_t; typedef unsigned long int __fsfilcnt64_t; typedef long int __ssize_t; typedef __off64_t __loff_t; typedef __quad_t *__qaddr_t; typedef char *__caddr_t; typedef long int __intptr_t; typedef unsigned int __socklen_t; # 37 "/usr/include/stdio.h" 2 3 4 # 45 "/usr/include/stdio.h" 3 4 struct _IO_FILE; typedef struct _IO_FILE FILE; # 65 "/usr/include/stdio.h" 3 4 typedef struct _IO_FILE __FILE; # 75 "/usr/include/stdio.h" 3 4 # 1 "/usr/include/libio.h" 1 3 4 # 32 "/usr/include/libio.h" 3 4 # 1 "/usr/include/_G_config.h" 1 3 4 # 15 "/usr/include/_G_config.h" 3 4 # 1 "/usr/lib/gcc/x86_64-linux-gnu/4.4.7/include/stddef.h" 1 3 4 # 16 "/usr/include/_G_config.h" 2 3 4 # 1 "/usr/include/wchar.h" 1 3 4 # 83 "/usr/include/wchar.h" 3 4 typedef struct { int __count; union { unsigned int __wch; char __wchb[4]; } __value; } __mbstate_t; # 21 "/usr/include/_G_config.h" 2 3 4 typedef struct { __off_t __pos; __mbstate_t __state; } _G_fpos_t; typedef struct { __off64_t __pos; __mbstate_t __state; } _G_fpos64_t; # 53 "/usr/include/_G_config.h" 3 4 typedef int _G_int16_t __attribute__ ((__mode__ (__HI__))); typedef int _G_int32_t __attribute__ ((__mode__ (__SI__))); typedef unsigned int _G_uint16_t __attribute__ ((__mode__ (__HI__))); typedef unsigned int _G_uint32_t __attribute__ ((__mode__ (__SI__))); # 33 "/usr/include/libio.h" 2 3 4 # 53 "/usr/include/libio.h" 3 4 # 1 "/usr/lib/gcc/x86_64-linux-gnu/4.4.7/include/stdarg.h" 1 3 4 # 40 "/usr/lib/gcc/x86_64-linux-gnu/4.4.7/include/stdarg.h" 3 4 typedef __builtin_va_list __gnuc_va_list; # 54 "/usr/include/libio.h" 2 3 4 # 172 "/usr/include/libio.h" 3 4 struct _IO_jump_t; struct _IO_FILE; # 182 "/usr/include/libio.h" 3 4 typedef void _IO_lock_t; struct _IO_marker { struct _IO_marker *_next; struct _IO_FILE *_sbuf; int _pos; # 205 "/usr/include/libio.h" 3 4 }; enum __codecvt_result { __codecvt_ok, __codecvt_partial, __codecvt_error, __codecvt_noconv }; # 273 "/usr/include/libio.h" 3 4 struct _IO_FILE { int _flags; char* _IO_read_ptr; char* _IO_read_end; char* _IO_read_base; char* _IO_write_base; char* _IO_write_ptr; char* _IO_write_end; char* _IO_buf_base; char* _IO_buf_end; char *_IO_save_base; char *_IO_backup_base; char *_IO_save_end; struct _IO_marker *_markers; struct _IO_FILE *_chain; int _fileno; int _flags2; __off_t _old_offset; unsigned short _cur_column; signed char _vtable_offset; char _shortbuf[1]; _IO_lock_t *_lock; # 321 "/usr/include/libio.h" 3 4 __off64_t _offset; # 330 "/usr/include/libio.h" 3 4 void *__pad1; void *__pad2; void *__pad3; void *__pad4; size_t __pad5; int _mode; char _unused2[15 * sizeof (int) - 4 * sizeof (void *) - sizeof (size_t)]; }; typedef struct _IO_FILE _IO_FILE; struct _IO_FILE_plus; extern struct _IO_FILE_plus _IO_2_1_stdin_; extern struct _IO_FILE_plus _IO_2_1_stdout_; extern struct _IO_FILE_plus _IO_2_1_stderr_; # 366 "/usr/include/libio.h" 3 4 typedef __ssize_t __io_read_fn (void *__cookie, char *__buf, size_t __nbytes); typedef __ssize_t __io_write_fn (void *__cookie, __const char *__buf, size_t __n); typedef int __io_seek_fn (void *__cookie, __off64_t *__pos, int __w); typedef int __io_close_fn (void *__cookie); # 418 "/usr/include/libio.h" 3 4 extern int __underflow (_IO_FILE *); extern int __uflow (_IO_FILE *); extern int __overflow (_IO_FILE *, int); # 462 "/usr/include/libio.h" 3 4 extern int _IO_getc (_IO_FILE *__fp); extern int _IO_putc (int __c, _IO_FILE *__fp); extern int _IO_feof (_IO_FILE *__fp) __attribute__ ((__nothrow__ )); extern int _IO_ferror (_IO_FILE *__fp) __attribute__ ((__nothrow__ )); extern int _IO_peekc_locked (_IO_FILE *__fp); extern void _IO_flockfile (_IO_FILE *) __attribute__ ((__nothrow__ )); extern void _IO_funlockfile (_IO_FILE *) __attribute__ ((__nothrow__ )); extern int _IO_ftrylockfile (_IO_FILE *) __attribute__ ((__nothrow__ )); # 492 "/usr/include/libio.h" 3 4 extern int _IO_vfscanf (_IO_FILE * __restrict, const char * __restrict, __gnuc_va_list, int *__restrict); extern int _IO_vfprintf (_IO_FILE *__restrict, const char *__restrict, __gnuc_va_list); extern __ssize_t _IO_padn (_IO_FILE *, int, __ssize_t); extern size_t _IO_sgetn (_IO_FILE *, void *, size_t); extern __off64_t _IO_seekoff (_IO_FILE *, __off64_t, int, int); extern __off64_t _IO_seekpos (_IO_FILE *, __off64_t, int); extern void _IO_free_backup_area (_IO_FILE *) __attribute__ ((__nothrow__ )); # 76 "/usr/include/stdio.h" 2 3 4 typedef __gnuc_va_list va_list; # 91 "/usr/include/stdio.h" 3 4 typedef __off_t off_t; # 103 "/usr/include/stdio.h" 3 4 typedef __ssize_t ssize_t; typedef _G_fpos_t fpos_t; # 165 "/usr/include/stdio.h" 3 4 # 1 "/usr/include/x86_64-linux-gnu/bits/stdio_lim.h" 1 3 4 # 166 "/usr/include/stdio.h" 2 3 4 extern struct _IO_FILE *stdin; extern struct _IO_FILE *stdout; extern struct _IO_FILE *stderr; extern int remove (__const char *__filename) __attribute__ ((__nothrow__ )); extern int rename (__const char *__old, __const char *__new) __attribute__ ((__nothrow__ )); extern int renameat (int __oldfd, __const char *__old, int __newfd, __const char *__new) __attribute__ ((__nothrow__ )); extern FILE *tmpfile (void) ; # 210 "/usr/include/stdio.h" 3 4 extern char *tmpnam (char *__s) __attribute__ ((__nothrow__ )) ; extern char *tmpnam_r (char *__s) __attribute__ ((__nothrow__ )) ; # 228 "/usr/include/stdio.h" 3 4 extern char *tempnam (__const char *__dir, __const char *__pfx) __attribute__ ((__nothrow__ )) __attribute__ ((__malloc__)) ; extern int fclose (FILE *__stream); extern int fflush (FILE *__stream); # 253 "/usr/include/stdio.h" 3 4 extern int fflush_unlocked (FILE *__stream); # 267 "/usr/include/stdio.h" 3 4 extern FILE *fopen (__const char *__restrict __filename, __const char *__restrict __modes) ; extern FILE *freopen (__const char *__restrict __filename, __const char *__restrict __modes, FILE *__restrict __stream) ; # 296 "/usr/include/stdio.h" 3 4 # 307 "/usr/include/stdio.h" 3 4 extern FILE *fdopen (int __fd, __const char *__modes) __attribute__ ((__nothrow__ )) ; # 320 "/usr/include/stdio.h" 3 4 extern FILE *fmemopen (void *__s, size_t __len, __const char *__modes) __attribute__ ((__nothrow__ )) ; extern FILE *open_memstream (char **__bufloc, size_t *__sizeloc) __attribute__ ((__nothrow__ )) ; extern void setbuf (FILE *__restrict __stream, char *__restrict __buf) __attribute__ ((__nothrow__ )); extern int setvbuf (FILE *__restrict __stream, char *__restrict __buf, int __modes, size_t __n) __attribute__ ((__nothrow__ )); extern void setbuffer (FILE *__restrict __stream, char *__restrict __buf, size_t __size) __attribute__ ((__nothrow__ )); extern void setlinebuf (FILE *__stream) __attribute__ ((__nothrow__ )); extern int fprintf (FILE *__restrict __stream, __const char *__restrict __format, ...); extern int printf (__const char *__restrict __format, ...); extern int sprintf (char *__restrict __s, __const char *__restrict __format, ...) __attribute__ ((__nothrow__)); extern int vfprintf (FILE *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg); extern int vprintf (__const char *__restrict __format, __gnuc_va_list __arg); extern int vsprintf (char *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __attribute__ ((__nothrow__)); extern int snprintf (char *__restrict __s, size_t __maxlen, __const char *__restrict __format, ...) __attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 4))); extern int vsnprintf (char *__restrict __s, size_t __maxlen, __const char *__restrict __format, __gnuc_va_list __arg) __attribute__ ((__nothrow__)) __attribute__ ((__format__ (__printf__, 3, 0))); # 418 "/usr/include/stdio.h" 3 4 extern int vdprintf (int __fd, __const char *__restrict __fmt, __gnuc_va_list __arg) __attribute__ ((__format__ (__printf__, 2, 0))); extern int dprintf (int __fd, __const char *__restrict __fmt, ...) __attribute__ ((__format__ (__printf__, 2, 3))); extern int fscanf (FILE *__restrict __stream, __const char *__restrict __format, ...) ; extern int scanf (__const char *__restrict __format, ...) ; extern int sscanf (__const char *__restrict __s, __const char *__restrict __format, ...) __attribute__ ((__nothrow__ )); # 449 "/usr/include/stdio.h" 3 4 extern int fscanf (FILE *__restrict __stream, __const char *__restrict __format, ...) __asm__ ("" "__isoc99_fscanf") ; extern int scanf (__const char *__restrict __format, ...) __asm__ ("" "__isoc99_scanf") ; extern int sscanf (__const char *__restrict __s, __const char *__restrict __format, ...) __asm__ ("" "__isoc99_sscanf") __attribute__ ((__nothrow__ )); # 469 "/usr/include/stdio.h" 3 4 extern int vfscanf (FILE *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __attribute__ ((__format__ (__scanf__, 2, 0))) ; extern int vscanf (__const char *__restrict __format, __gnuc_va_list __arg) __attribute__ ((__format__ (__scanf__, 1, 0))) ; extern int vsscanf (__const char *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __attribute__ ((__nothrow__ )) __attribute__ ((__format__ (__scanf__, 2, 0))); # 500 "/usr/include/stdio.h" 3 4 extern int vfscanf (FILE *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vfscanf") __attribute__ ((__format__ (__scanf__, 2, 0))) ; extern int vscanf (__const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vscanf") __attribute__ ((__format__ (__scanf__, 1, 0))) ; extern int vsscanf (__const char *__restrict __s, __const char *__restrict __format, __gnuc_va_list __arg) __asm__ ("" "__isoc99_vsscanf") __attribute__ ((__nothrow__ )) __attribute__ ((__format__ (__scanf__, 2, 0))); # 528 "/usr/include/stdio.h" 3 4 extern int fgetc (FILE *__stream); extern int getc (FILE *__stream); extern int getchar (void); # 556 "/usr/include/stdio.h" 3 4 extern int getc_unlocked (FILE *__stream); extern int getchar_unlocked (void); # 567 "/usr/include/stdio.h" 3 4 extern int fgetc_unlocked (FILE *__stream); extern int fputc (int __c, FILE *__stream); extern int putc (int __c, FILE *__stream); extern int putchar (int __c); # 600 "/usr/include/stdio.h" 3 4 extern int fputc_unlocked (int __c, FILE *__stream); extern int putc_unlocked (int __c, FILE *__stream); extern int putchar_unlocked (int __c); extern int getw (FILE *__stream); extern int putw (int __w, FILE *__stream); extern char *fgets (char *__restrict __s, int __n, FILE *__restrict __stream) ; extern char *gets (char *__s) ; # 662 "/usr/include/stdio.h" 3 4 extern __ssize_t __getdelim (char **__restrict __lineptr, size_t *__restrict __n, int __delimiter, FILE *__restrict __stream) ; extern __ssize_t getdelim (char **__restrict __lineptr, size_t *__restrict __n, int __delimiter, FILE *__restrict __stream) ; extern __ssize_t getline (char **__restrict __lineptr, size_t *__restrict __n, FILE *__restrict __stream) ; extern int fputs (__const char *__restrict __s, FILE *__restrict __stream); extern int puts (__const char *__s); extern int ungetc (int __c, FILE *__stream); extern size_t fread (void *__restrict __ptr, size_t __size, size_t __n, FILE *__restrict __stream) ; extern size_t fwrite (__const void *__restrict __ptr, size_t __size, size_t __n, FILE *__restrict __s); # 734 "/usr/include/stdio.h" 3 4 extern size_t fread_unlocked (void *__restrict __ptr, size_t __size, size_t __n, FILE *__restrict __stream) ; extern size_t fwrite_unlocked (__const void *__restrict __ptr, size_t __size, size_t __n, FILE *__restrict __stream); extern int fseek (FILE *__stream, long int __off, int __whence); extern long int ftell (FILE *__stream) ; extern void rewind (FILE *__stream); # 770 "/usr/include/stdio.h" 3 4 extern int fseeko (FILE *__stream, __off_t __off, int __whence); extern __off_t ftello (FILE *__stream) ; # 789 "/usr/include/stdio.h" 3 4 extern int fgetpos (FILE *__restrict __stream, fpos_t *__restrict __pos); extern int fsetpos (FILE *__stream, __const fpos_t *__pos); # 812 "/usr/include/stdio.h" 3 4 # 821 "/usr/include/stdio.h" 3 4 extern void clearerr (FILE *__stream) __attribute__ ((__nothrow__ )); extern int feof (FILE *__stream) __attribute__ ((__nothrow__ )) ; extern int ferror (FILE *__stream) __attribute__ ((__nothrow__ )) ; extern void clearerr_unlocked (FILE *__stream) __attribute__ ((__nothrow__ )); extern int feof_unlocked (FILE *__stream) __attribute__ ((__nothrow__ )) ; extern int ferror_unlocked (FILE *__stream) __attribute__ ((__nothrow__ )) ; extern void perror (__const char *__s); # 1 "/usr/include/x86_64-linux-gnu/bits/sys_errlist.h" 1 3 4 # 27 "/usr/include/x86_64-linux-gnu/bits/sys_errlist.h" 3 4 extern int sys_nerr; extern __const char *__const sys_errlist[]; # 851 "/usr/include/stdio.h" 2 3 4 extern int fileno (FILE *__stream) __attribute__ ((__nothrow__ )) ; extern int fileno_unlocked (FILE *__stream) __attribute__ ((__nothrow__ )) ; # 870 "/usr/include/stdio.h" 3 4 extern FILE *popen (__const char *__command, __const char *__modes) ; extern int pclose (FILE *__stream); extern char *ctermid (char *__s) __attribute__ ((__nothrow__ )); # 910 "/usr/include/stdio.h" 3 4 extern void flockfile (FILE *__stream) __attribute__ ((__nothrow__ )); extern int ftrylockfile (FILE *__stream) __attribute__ ((__nothrow__ )) ; extern void funlockfile (FILE *__stream) __attribute__ ((__nothrow__ )); # 940 "/usr/include/stdio.h" 3 4 # 2 "demo01.c" 2 void main() { printf("Pi is %d\n",3.1415926); printf("hello world\n"); getchar(); }
其中展开了包含的头文件stdio.h,以及宏替换
void main() { printf("Pi is %d\n",3.1415926); // 宏替换 printf("hello world\n"); getchar(); }
3、编译阶段：
gcc -S demo01.i -o demo01.s // 编译，生成汇编代码
编译后的代码，生成汇编代码
.file "demo01.c" .section .rodata .LC0: .string "Pi is %f\n" .LC2: .string "hello world" .text .globl main .type main, @function main: .LFB0: .cfi_startproc pushq %rbp .cfi_def_cfa_offset 16 movq %rsp, %rbp .cfi_offset 6, -16 .cfi_def_cfa_register 6 movl $.LC0, %eax movsd .LC1(%rip), %xmm0 movq %rax, %rdi movl $1, %eax call printf movl $.LC2, %edi call puts call getchar leave ret .cfi_endproc .LFE0: .size main, .-main .section .rodata .align 8 .LC1: .long 1293080650 .long 1074340347 .ident "GCC: (Ubuntu/Linaro 4.4.7-1ubuntu2) 4.4.7" .section .note.GNU-stack,"",@progbits
4、汇编阶段
as demo01.s -o demo01.o // 汇编，生成机器代码
生成的二进制机器代码
5、连接阶段
gcc demo01.o -o deo01.exe // 在Windows下生成该文件，在Ubuntu下编译的，在Windows上运行不通过，在Linux下运行也不通过 gcc demo01.o -o deo01 // 在Linux下生成该文件，可在Linux下运行
连接后生成的文件也是二进制机器代码
执行可执行文件
./deo01 Pi is 3.141593 hello world
3. 链接阶段演示
1 #include <stdio.h> 2 3 void main(void) 4 { 5 printf("my entry test.\n"); 6 }
1.源文件编译，生成可重定向文件*.o，生成main.o
gcc -c main.c
2. 连接源文键以及库文件，可以执行并且显示出来，生成可执行文件
ld -o main main.o -dynamic-linker /lib64/ld-linux-x86-64.so.2 /usr/lib/x86_64-linux-gnu/crt1.o /usr/lib/x86_64-linux-gnu/crti.o /usr/lib/x86_64-linux-gnu/crtn.o -lc
1. ld: 链接器
2. -o:指定输出可执行文件名
3. 动态链接器指定连接时需要的动态库
4. crt1.o crti.o crtn.o为C运行时初始化的文件,参考：crt1.o, crti.o, crtbegin.o, crtend.o, crtn.o-CSDN博客
5. -lc链接与标准库相关
3. 验证执行文件
4.连接脚本：参考：gcc链接脚本ld 实例讲解 - solonj - 博客园
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