结构体应用及其字节对齐问题
在单片机中,结构体操作及其字节对齐问题(以LCD菜单为例)
#include <stdio.h> typedef struct MenuItem {//28字节 char cursorPosition; //1 byte unsigned char menuItemTotal; //1 byte bool isSelect; //1 byte //此处自动补充1个字节,字节对齐 const unsigned char *icoSelected; //4 byte const unsigned char *icoUnselected; //4 byte const char *title; //4 byte void (*Function)(void); //4 byte struct MenuItem* parentMenu; //4 byte struct MenuItem* childrenMenu; //4 byte }MenuItem_typedef; const char* mainMenuLanguage[3][10] = { {"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",}, {"1.param set","2.password modify","3.exit","4.exit","5.exit","6.exit","7.exit","8.exit","9.exit","10.exit",}, {"1.參數設置","2.密碼修改","3.退出","4.exit","5.exit","6.exit","7.exit","8.exit","9.exit","10.exit",}, }; //变量声明 MenuItem_typedef menuL1_dev[10]; MenuItem_typedef* pCurItem; const char * pCurTitle; int main(void) { for(int i=0; i<10; i++) { menuL1_dev[i].cursorPosition = NULL; menuL1_dev[i].menuItemTotal = 10; menuL1_dev[i].isSelect = false; menuL1_dev[i].icoSelected = NULL;//ico menuL1_dev[i].icoUnselected = NULL; menuL1_dev[i].title = mainMenuLanguage[0][i]; menuL1_dev[i].Function = NULL; menuL1_dev[i].parentMenu = NULL; menuL1_dev[i].childrenMenu = NULL; } printf("%d \n", sizeof(const unsigned char *));//4字节 printf("%d \n", sizeof(void (*)(void)));//函数指针4字节 printf("%d \n", sizeof(bool));//1字节 printf("%d \n", sizeof(struct MenuItem));//28字节 printf("%d \n", sizeof(struct MenuItem *));//4字节 printf("%d \n", sizeof(menuL1_dev));//280字节 printf("menuL1_dev addr=%d \n", menuL1_dev);//addr1 = 4339288 pCurItem = menuL1_dev + 1; printf("pCurItem addr=%d \n", pCurItem);//addr2= addr1+28 = 4339316 pCurTitle = menuL1_dev->title + 2; printf("pCurTitle=%s \n", pCurTitle);//参数设置 pCurTitle = (menuL1_dev+1)->title + 4; printf("pCurTitle=%s \n", pCurTitle);//码设置 return 0; }