class X{public:    double a;    float b;    short c;    char d;};

由于double占8Byte，float占4Byte，int占4Byte，short占2Byte，char占1Byte，

在VC6.0中按照最大字节数进行对齐，sizeof(X)=16

class X{public:
    float b;
    double a;        short c;    char d;};//sizeof(X)=24

class X{public:    double a;    float b;    short c;    char d;};
在Linux中对齐按照最大4个字节对齐，没有8个字节，所以sizeof(X)=16
class X{public:
    float b;
    double a;        short c;    char d;};//sizeof(X)=16

class X{public:
    //float b;
    double a;        short c;    char d;};//sizeof(X)=12

class X{public:
    float b;
    //double a;       // short c;    char d;};//sizeof(X)=8