1 #include <stdio.h>
2
3 int a = 0x12345678;
4 int a2 = 0x12345678;
5 int a3 = 0x12345678;
6 int a4 = 0x12345678;
7 int main()
8 {
9 int b = 0x12345678;
10 int b2 = 0x12345678;
11 int b3 = 0x12345678;
12 int b4 = 0x12345678;
13 char *p1,*p2,*p3,p5;
14 int *p4,p6;
15
16
17 char *c = "hello";
18
19 p1 = &b;
20 *p2 = &b;
21 p3 = &a;
22 p4 = &a;
23 *p4 = *p4+1;
24 p5 = a;
25 p6 = a;
26 printf("hello world\n");
27 printf("int a addr is: %p\n",&a);
28 printf("int a2 addr is: %p\n",&a2);
29 printf("int a4 addr is: %p\n",&a3);
30 printf("int a3 addr is: %p\n",&a4);
31 printf("int b addr is: %p\n",&b);
32 printf("int b2 addr is: %p\n",&b2);
33 printf("int b3 addr is: %p\n",&b3);
34 printf("int b4 addr is: %p\n",&b4);
35 printf("int main addr is: %p\n",main);
36 printf("===========================\n");
37
38 printf("pointer p1 addr is: %p\n",p1);
39 printf("*p1 addr is: %p\n",*p1);
40 printf("pointer p3 addr is: %p\n",p3);
41 printf("*p3 addr is: %p\n",*p3);
42 printf("pointer p4 addr is: %p\n",p4);
43 printf("*p4 addr is: %p\n",*p4);
44 printf("pointer p2 addr is: %p\n",p2);
45 printf("*p2 addr is: %p\n",*p2);
46 printf("===========================\n");
47 printf("char p5 is : %p\n",p5);
48 printf("int p6 is:%p\n",p6);
49
50 printf("============================\n");
51 printf("str addr is: %p\n","hello");
52 printf("str addr is: %p\n",&"hello");
53 printf("============================\n");
54 printf("str addr is: %s\n",c);
55 printf("str addr is: %p\n",c);
56 printf("str addr is: %p\n",&c);
57
58 return 0;
59 }
60 /*
61 C:\Users\shuai\Desktop\c>gcc -o build 001.c & build
62 001.c: In function 'main':
63 001.c:14:5: warning: assignment from incompatible pointer type [-Wincompatible-p
64 ointer-types]
65 p1 = &b;
66 ^
67 001.c:15:6: warning: assignment makes integer from pointer without a cast [-Wint
68 -conversion]
69 *p2 = &b;
70 ^
71 001.c:16:5: warning: assignment from incompatible pointer type [-Wincompatible-p
72 ointer-types]
73 p3 = &a;
74 ^
75 hello world
76 int a addr is: 0x402008
77 int a2 addr is: 0x40200c
78 int a4 addr is: 0x402010
79 int a3 addr is: 0x402014
80 int b addr is: 0x28cc44
81 int b2 addr is: 0x28cc40
82 int b3 addr is: 0x28cc3c
83 int b4 addr is: 0x28cc38
84 int main addr is: 0x4011d0
85 ===========================
86 pointer p1 addr is: 0x28cc44
87 *p1 addr is: 0x78
88 pointer p3 addr is: 0x402008
89 *p3 addr is: 0x79
90 pointer p4 addr is: 0x402008
91 *p4 addr is: 0x12345679
92 pointer p2 addr is: 0x612b5060
93 *p2 addr is: 0x44
94 ===========================
95 char p5 is : 0x79
96 int p6 is:0x12345679
97 ============================
98 str addr is: 0x403060
99 str addr is: 0x403060
100 ============================
101 str addr is: hello
102 str addr is: 0x403060
103 str addr is: 0x28cc40
104
105
106 */
107
108 /*
109 结论:
110 1 系统中全局数据空间地址从小往大排列
111 系统中栈空间地址从栈顶往小排列
112 其中貌似main最先初始化,然后才有了后续事件
113 2 *p=*p+1 实际上是指针+1 等效于*p=*(p+1) 即对指针操作
114 *p=(*p)+1 指的是p地址上的数据+1 即对数据操作 注意两者不同
115 3 char *c="hello" ("%p\n",c)和("%p\n","hello")和("%p\n",&"hello")结果一样都是常量"hello"地址
116 ("%p\n",&c)取得是c的地址
117 ("%s\n",c)输出hello
118 4 *p=&b慎用,看起来不伦不类.并且结果未知,(*p==b?)
119 推荐使用p=&b,再*p即是b的值(*p==b为真)
120
121
122 */
