1.基本理解
比如：struct TEST
{
char a;
int b;
char c;
}
那么经过sizeof后得出结果是 12， 因为默认内存占用4byte， 变量a占用1byte，剩下3个，不足以存放变量b，故变量a也占用了4byte， 变量c由于后面没有了数据， 也会变为4byte，最后sizeof值为12。
#include "stdafx.h" #include <iostream> using namespace std; struct TEST1 //12 { char a; int b; char c; }; struct TEST2 //8 { char a; char b; int c; }; struct TEST3 //8 { char a; char b; char c; int d; }; struct TEST4 //12 { char a[5]; int b; }; struct TEST5 //8 + 8 + 8 = 24 { double a; //8 char b; //4 int c; //4,location the b memery char d[5]; //5 }; int _tmain(int argc, _TCHAR* argv[]) { struct TEST1 t1; struct TEST2 t2; struct TEST3 t3; struct TEST4 t4; struct TEST5 t5; cout << sizeof(t1) << endl << sizeof(t2) << endl; cout << sizeof(t3) << endl << sizeof(t4) << endl << sizeof(t5) << endl; return 0; } |
