内存字节对齐

#pragma pack(8)
struct A
{
	char a;
	short b;
};
struct B
{
	char c;
	A d;
	long long e;
};
#pragma pack()

A stA;
B stB;
stB.c = 1;
stB.d.a = 2;
stB.d.b = 3;
stB.e = 4;
A *pA = &stA;
B *pB = &stB;
sizeof(A);
sizeof(B);

sizeof(A) ：4

sizeof(B) ：16



B的内存：01 cc 02 cc 03 00 cc cc 04 00 00 00 00 00 00 00

#pragma pack(8)
struct A
{
	char a;
	long b;
};
struct B
{
	char c;
	A d;
	long long e;
};
#pragma pack()

A stA;
B stB;
stB.c = 1;
stB.d.a = 2;
stB.d.b = 3;
stB.e = 4;
A *pA = &stA;
B *pB = &stB;
sizeof(A);
sizeof(B);

sizeof(A) ：8

sizeof(B) ：24

B的内存：01 cc cc cc 02 cc cc cc 03 00 00 00 cc cc cc cc 04 00 00 00 00 00 00 00