1 #include<stdio.h>
2 #include<unistd.h>
3 main()
4 {
5 //situation 1
6 //int *p = sbrk(4); // Here we allocate 1024(decides to the system) bytes of memory and move(not allocate) 4 bytes forward and then return.
7 //*p = 8888;
8 //printf("%d
",*p);
9
10
11 //situation 2
12 //int *p = sbrk(0);//Segmentation fault(core dumped)
13 //*p = 8888;
14 //printf("%d
",*p);
15
16
17 //situation 3
18 //int *p = sbrk(0);
19 //brk(p+1);
20 //*p = 8888;
21 //printf("%d
",*p);
22
23 //situation 4
24 //int *p = sbrk(4);
25 //*(p+20) = 100;// You will not get a core dumped here ,but this use is illegal and you may get an unpredictable error.
26
27 //situation 5
28 //int *p = sbrk(0);
29 //brk(p+4); // Here we
30 //printf("%d
",*(p+20)); //0
31 //*(p+20) = 100;
32 //printf("%d
",*(p+20)); //100
33 //*(p+1023) = 100;
34 //*(p+1024) = 100; You will get a core dumped
35
36 /*
37 int *p1 = sbrk(4); //Allocate and move
38 int *p2 = sbrk(4); //move
39 int *p3 = sbrk(4); //move
40 int *p4 = sbrk(4); //move
41 int *p5 = sbrk(4); //move
42 int *p6 = sbrk(4); //move
43 int *p7 = sbrk(0); //move
44 int *p8 = sbrk(0); //move
45 brk(p8-1);
46
47 printf("%p
",p1);
48 printf("%p
",p2);
49 printf("%p
",p3);
50 printf("%p
",p4);
51 printf("%p
",p5);
52 printf("%p
",p6);
53 printf("%p
",p7);
54 printf("%p
",p8);
55
56 *p6 = 8888;
57 *p7 = 9999;
58 *p8 = 10000;
59 printf("%d,%d,%d
",*p6,*p7,*p8);*/
60
61
62
63 int *p = sbrk(0); //Allocate and return a point(the value is null)
64 printf("%p
",p);
65 brk(p+4);//don't move
66 printf("%p
",p);
67 brk(p+4);//don't move
68 printf("%p
",p);
69 brk(p+4);//don't move
70 printf("%p
",p);
71 brk(p);//don't move
72 printf("%p
",p);
73
74
75 }