结合“hello world”探讨gcc编译程序的过程

`-o FILE'

     Place output in file FILE.  This applies regardless to whatever sort of output is being produced, whether it be an executable file, an object file, an assembler file or preprocessed C code.

     If `-o' is not specified, the default is to put an executable file in `a.out', the object file for `SOURCE.SUFFIX' in `SOURCE.o', its assembler file in `SOURCE.s', a precompiled header file in `SOURCE.SUFFIX.gch', and all preprocessed C source on standard output.

    指定输出文件为FILE，该选项不考虑GCC产生什么输出，无论是可执行文件、目标文件、汇编文件还是预处理后的C代码。

    如果没有使用`-o'选项，默认的输出结果是:可执行文件为a.out，source.suffix的目标文件是source.o，汇编文件是source.s，而预处理后的C代码送往标准输出。

#include <stdio.h>

int main(int argc, char **argv)

{

    printf("Hello World! via %x\n", printf);

    return 0;

}

`-E'

     Stop after the preprocessing stage; do not run the compiler proper. The output is in the form of preprocessed source code, which is sent to the standard output.

     Input files which don't require preprocessing are ignored.

    预处理后停止，不进行编译。预处理后的代码送往标准输出。GCC忽略任何不需要预处理的输入文件。

# 1 "hello.c"

# 1 "<built-in>"

# 1 "<command line>"

# 1 "hello.c"

# 1 "/usr/include/stdio.h" 1 3 4

# 28 "/usr/include/stdio.h" 3 4

# 1 "/usr/include/features.h" 1 3 4

# 335 "/usr/include/features.h" 3 4

# 1 "/usr/include/sys/cdefs.h" 1 3 4

# 360 "/usr/include/sys/cdefs.h" 3 4

# 1 "/usr/include/bits/wordsize.h" 1 3 4

# 361 "/usr/include/sys/cdefs.h" 2 3 4

# 336 "/usr/include/features.h" 2 3 4

# 359 "/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

# 8 "/usr/include/gnu/stubs.h" 2 3 4

# 360 "/usr/include/features.h" 2 3 4

# 29 "/usr/include/stdio.h" 2 3 4

# 1 "/usr/lib/gcc/i386-RedHat-linux/4.1.2/include/stddef.h" 1 3 4

# 214 "/usr/lib/gcc/i386-redhat-linux/4.1.2/include/stddef.h" 3 4

typedef unsigned int size_t;

# 35 "/usr/include/stdio.h" 2 3 4

# 1 "/usr/include/bits/types.h" 1 3 4

# 28 "/usr/include/bits/types.h" 3 4

# 1 "/usr/include/bits/wordsize.h" 1 3 4

# 29 "/usr/include/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;

__extension__ typedef signed long long int __int64_t;

__extension__ typedef unsigned long long int __uint64_t;

__extension__ typedef long long int __quad_t;

__extension__ typedef unsigned long long int __u_quad_t;

# 131 "/usr/include/bits/types.h" 3 4

# 1 "/usr/include/bits/typesizes.h" 1 3 4

# 132 "/usr/include/bits/types.h" 2 3 4

...

`-S'

     Stop after the stage of compilation proper; do not assemble.  The output is in the form of an assembler code file for each non-assembler input file specified.

     By default, the assembler file name for a source file is made by replacing the suffix `.c', `.i', etc., with `.s'. Input files that don't require compilation are ignored.

     编译后即停止，不进行汇编。对于每个输入的非汇编语言文件，输出文件是汇编语言文件。

     缺省情况下，GCC通过用`.o'替换源文件名后缀`.c',`.i'等以产生目标文件名。可以使用-o选项指定选择其他名字。GCC忽略任何不需要编译的输入文件。

  .file        "hello.c"

  .section        .rodata

.LC0:

  .string        "Hello World! via %x\n"

  .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        $20, %esp

  movl        $printf, 4(%esp)

  movl        $.LC0, (%esp)

  call        printf

  movl        $0, %eax

  addl        $20, %esp

  popl        %ecx

  popl        %ebp

  leal        -4(%ecx), %esp

  ret

  .size        main, .-main

  .ident        "GCC: (GNU) 4.1.2 20070925 (Red Hat 4.1.2-33)"

  .section        .note.GNU-stack,"",@progbits