内存对齐

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