017 exit()函数

/*************************017.c exit()函数************************
*  C 语言编程百例的第17个例子：
*输入月数，程序打印出1999年的该月有几天。
*/
#include<stdlib.h>
#include<stdio.h>

void main()
{
//定义变量month和day存放月数和天数
int month;
int day;

printf("please input the month number:");
scanf("%d",&month);
switch(month)
{
//当输入为1、3、5、7、8、10和12月时：
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
day=31;
break; //每天天数都是31天，跳出循环
//当输入为4、6、9、和11月时
case 4:
case 6:
case 9:
case 11:
day=30;
break; //每天都是30天，跳出循环
case 2:
day=28;
break;
default:
exit(0);
}

printf("1999.%d has %d days.\n",month,day);
}

.file	"017.c"
.def	___main;	.scl	2;	.type	32;	.endef
.text
.align 32
LC0:
.ascii "please input the month number:\0"
LC1:
.ascii "%d\0"
LC2:
.ascii "1999.%d has %d days.\12\0"
.align 2
.globl _main
.def	_main;	.scl	2;	.type	32;	.endef
_main:
pushl	%ebp
movl	%esp, %ebp
subl	$24, %esp
andl	$-16, %esp
movl	$0, %eax
movl	%eax, -12(%ebp)
movl	-12(%ebp), %eax
call	__alloca
call	___main
subl	$12, %esp         #printf("please input the month number:");
pushl	$LC0
call	_printf
addl	$16, %esp
subl	$8, %esp         #scanf("%d",&month);
leal	-4(%ebp), %eax
pushl	%eax
pushl	$LC1
call	_scanf
addl	$16, %esp
cmpl	$12, -4(%ebp)   # month和12 比
ja	L28             # 大于调到 exit(0)
movl	-4(%ebp), %eax  # eax=month
sall	$2, %eax        # eax =eax* 4  (跳转编号4位对其)
movl	L29(%eax), %eax # eax = L29:%eax
jmp	*%eax
.p2align 2
.align 4
L29:
.long	L28
.long	L22
.long	L27
.long	L22
.long	L26
.long	L22
.long	L26
.long	L22
.long	L22
.long	L26
.long	L22
.long	L26
.long	L22
L22:
movl	$31, -8(%ebp)
jmp	L15
L26:
movl	$30, -8(%ebp)
jmp	L15
L27:
movl	$28, -8(%ebp)
jmp	L15
L28:
subl	$12, %esp     #调用exit函数，
pushl	$0
call	_exit         #退出程序
L15:
subl	$4, %esp
pushl	-8(%ebp)
pushl	-4(%ebp)
pushl	$LC2
call	_printf
addl	$16, %esp
leave
ret
.def	_exit;	.scl	2;	.type	32;	.endef
.def	_scanf;	.scl	2;	.type	32;	.endef
.def	_printf;	.scl	2;	.type	32;	.endef