c++ - Struct size stays the same even after adding a new member to it -

c++ - Struct size stays the same even after adding a new member to it -

when execute

cout << sizeof(string);

i got 8 answer.

now having structure

typedef struct { int a; string str; } mytype;

and executing

cout << sizeof(mytype);

i got 16 answer.

now made alter in structure

typedef struct { int a, b; string str; } mytype;

and executing

cout << sizeof(mytype);

i got 16 answer!!!. how? happening?

perhaps padding happening. e.g. sizeof(int) can 4 bytes , compiler can add together 4 bytes after a sake of info alignment. layout this:

typedef struct { int a; // 4 bytes // 4 bytes padding string str; // 8 bytes } mytype; typedef struct { int a; // 4 bytes int b; // 4 bytes string str; // 8 bytes } mytype;

c++ string struct