结构体应用及其字节对齐问题

 1 #include <stdio.h>
 2 
 3 typedef struct MenuItem{//28字节
 4 
 5   char cursorPosition;                //1 byte
 6   unsigned char menuItemTotal;        //1 byte
 7   bool isSelect;                      //1 byte
 8   //此处自动补充1个字节，字节对齐
 9   const unsigned char *icoSelected;   //4 byte
10   const unsigned char *icoUnselected; //4 byte
11   const char *title;                  //4 byte
12   void (*Function)(void);             //4 byte
13   struct MenuItem* parentMenu;        //4 byte
14   struct MenuItem* childrenMenu;      //4 byte
15 }MenuItem_typedef;
16 
17 
18 const char* mainMenuLanguage[3][10] = {
19   {"1.参数设置","2.密码修改","3.退出","4.退出","5.退出","6.退出","7.退出","8.退出","9.退出","10.退出",},
20   {"1.param set","2.password modify","3.exit","4.exit","5.exit","6.exit","7.exit","8.exit","9.exit","10.exit",},
21   {"1.exit","2.exit","3.exit","4.exit","5.exit","6.exit","7.exit","8.exit","9.exit","10.exit",},
22 };
23 
24 
25 //变量声明
26 MenuItem_typedef  menuL1_dev[10];
27 MenuItem_typedef* pCurItem;
28 const char * pCurTitle;
29 
30 int main(void)
31 {
32   for(int i=0; i<10; i++)
33   {
34     menuL1_dev[i].cursorPosition = NULL;
35     menuL1_dev[i].menuItemTotal = 10;
36     menuL1_dev[i].isSelect = false;
37     menuL1_dev[i].icoSelected = NULL;//ico
38     menuL1_dev[i].icoUnselected = NULL;
39     menuL1_dev[i].title = mainMenuLanguage[0][i];
40     menuL1_dev[i].Function = NULL;
41     menuL1_dev[i].parentMenu = NULL;
42     menuL1_dev[i].childrenMenu = NULL;
43   }
44 
45   printf("%d \n", sizeof(const unsigned char *));//4字节
46   printf("%d \n", sizeof(void (*)(void)));//函数指针4字节
47   printf("%d \n", sizeof(bool));//1字节
48   printf("%d \n", sizeof(struct MenuItem));//28字节
49   printf("%d \n", sizeof(struct MenuItem *));//4字节
50   printf("%d \n", sizeof(menuL1_dev));//280字节
51 
52   printf("menuL1_dev addr=%d \n", menuL1_dev);//addr1 = 4339288
53   pCurItem = menuL1_dev + 1;
54   printf("pCurItem addr=%d \n", pCurItem);//addr2= addr1+28 = 4339316
55 
56   pCurTitle = menuL1_dev->title + 2;
57   printf("pCurTitle=%s \n", pCurTitle);//参数设置
58 
59   pCurTitle = (menuL1_dev+1)->title + 4;
60   printf("pCurTitle=%s \n", pCurTitle);//码设置
61 
62   return 0;
63 }