[转]GCC编译过程的4个阶段

GCC编译过程的4个阶段

文章分类:C++编程

  在使用GCC编译程序时，其编译过程可以分为4个阶段：预处理(Pre-Processing) －> 编译(Compling) -> 汇编(Assembling) -> 连接(Linking) .

  程序员完全可以根据自己的需要让gcc在编译的任何一个阶段结束，检查活使用编译起在该阶段输出的信息，或者对其生成的二进制文件进行控制。

   我想通过一个Hello World程序对GCC的编译过程有进一步的认识。

[Xredman@localhost demo]$ cat test.c
#include

int main(void)
{
        printf("Hello World\n");
        return 0;
}

[Xredman@localhost demo]$ cat test.c
#include 

int main(void)
{
        printf("Hello World\n");
        return 0;
}

  首先来个一步到位编译成可执行文件

[Xredman@localhost demo]$ gcc -Wall test.c -o test.o
[Xredman@localhost demo]$ ./test.o
Hello World

[Xredman@localhost demo]$ gcc -Wall test.c -o test.o
[Xredman@localhost demo]$ ./test.o 
Hello World

   OK，这是我日常生活中所用的，以下将分步骤演示

   A.预处理(Pr-Processing)

 

gcc -E test.c -o test.i

gcc -E test.c -o test.i

   打开test.i文件，吓我嘛，编译器原来为我们做了这么多事，辛苦了。这里主要负责展开在源文件中定义的宏，并向其中插入#include语句所包含的内容

# 1 "test.c"
# 1 ""
# 1 ""
# 1 "test.c"
# 1 "/usr/include/stdio.h" 1 3 4
# 28 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/features.h" 1 3 4
# 329 "/usr/include/features.h" 3 4
# 1 "/usr/include/sys/cdefs.h" 1 3 4
# 313 "/usr/include/sys/cdefs.h" 3 4
# 1 "/usr/include/bits/wordsize.h" 1 3 4
# 314 "/usr/include/sys/cdefs.h" 2 3 4
# 330 "/usr/include/features.h" 2 3 4
# 352 "/usr/include/features.h" 3 4
# 1 "/usr/include/gnu/stubs.h" 1 3 4



# 1 "/usr/include/bits/wordsize.h" 1 3 4
# 5 "/usr/include/gnu/stubs.h" 2 3 4


# 1 "/usr/include/gnu/stubs-32.h" 1 3 4
....

# 1 "test.c"
# 1 ""
# 1 ""
# 1 "test.c"
# 1 "/usr/include/stdio.h" 1 3 4
# 28 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/features.h" 1 3 4
# 329 "/usr/include/features.h" 3 4
# 1 "/usr/include/sys/cdefs.h" 1 3 4
# 313 "/usr/include/sys/cdefs.h" 3 4
# 1 "/usr/include/bits/wordsize.h" 1 3 4
# 314 "/usr/include/sys/cdefs.h" 2 3 4
# 330 "/usr/include/features.h" 2 3 4
# 352 "/usr/include/features.h" 3 4
# 1 "/usr/include/gnu/stubs.h" 1 3 4



# 1 "/usr/include/bits/wordsize.h" 1 3 4
# 5 "/usr/include/gnu/stubs.h" 2 3 4


# 1 "/usr/include/gnu/stubs-32.h" 1 3 4
....

 B.编译(Compiling)

[Xredman@localhost demo]$ gcc -S test.i -o test.s

[Xredman@localhost demo]$ gcc -S test.i -o test.s

   编译之后应该就是汇编程序了吧，查看内容如下

[Xredman@localhost demo]$ cat test.s
        .file   "test.c"
        .section        .rodata
.LC0:
        .string "Hello World"
        .text
.globl main
        .type   main, @function
main:
        leal    4(%esp), %ecx
        andl    $-16, %esp
        pushl   -4(%ecx)
        pushl   %ebp
        movl    %esp, %ebp
        pushl   %ecx
        subl    $4, %esp
        movl    $.LC0, (%esp)
        call    puts
        movl    $0, %eax
        addl    $4, %esp
        popl    %ecx
        popl    %ebp
        leal    -4(%ecx), %esp
        ret
        .size   main, .-main
        .ident  "GCC: (GNU) 4.1.2 20080704 (Red Hat 4.1.2-48)"
        .section        .note.GNU-stack,"",@progbits

[Xredman@localhost demo]$ cat test.s
        .file   "test.c"
        .section        .rodata
.LC0:
        .string "Hello World"
        .text
.globl main
        .type   main, @function
main:
        leal    4(%esp), %ecx
        andl    $-16, %esp
        pushl   -4(%ecx)
        pushl   %ebp
        movl    %esp, %ebp
        pushl   %ecx
        subl    $4, %esp
        movl    $.LC0, (%esp)
        call    puts
        movl    $0, %eax
        addl    $4, %esp
        popl    %ecx
        popl    %ebp
        leal    -4(%ecx), %esp
        ret
        .size   main, .-main
        .ident  "GCC: (GNU) 4.1.2 20080704 (Red Hat 4.1.2-48)"
        .section        .note.GNU-stack,"",@progbits

 

  C.汇编(Assembling)

    汇编这一步是将汇编程序翻译成机器码，这也就决定了生成的程序能运行在哪种平台下，传说中GCC将调用gas汇编器

[Xredman@localhost demo]$ gcc -c test.s -o test.o

[Xredman@localhost demo]$ gcc -c test.s -o test.o

   D.连接(Linking)

   这是最后一步，将生成的目标文件和其所依赖的库文件进行连接，生成一个可执行文件。

[Xredman@localhost demo]$ gcc test.o -o test
[Xredman@localhost demo]$ ./test
Hello World

[Xredman@localhost demo]$ gcc test.o -o test
[Xredman@localhost demo]$ ./test
Hello World

 OK，练习完毕，我已经知道GCC的基本工作过程了。