C++ struct alignment - can save you memory

 the orders of members in a struct affect sizeof of struct 

see this example https://www.joshcaratelli.com/blog/struct-packing

if no compiler directive - memory align to 8 bytes by default

struct top

{

    char* p; //8 bytes

    int i;  //4 bytes

    short s; // 2 bytes

    char c;  // 1 byte

                    // 1 padding 

    int t; // 4 bytes

                    // 4 padding 

};

struct buttom

{

    char c; // 1 bytes -- 7 padding

    char* p; //8 bytes

    short s;  //2 bytes

    int i;   //4 bytes

               // 2 padding

    int t;  // 4 bytes 

               // 4 padding

        

};

    int sizeTop = sizeof(top);   // =>24

    int sizeButtom = sizeof(buttom); // =>32