c++ - structures and pointer arithmetic -

    #include <iostream>     #include <cmath>      using namespace std;        struct demo{        int one;        int two;        int three;      };     int main()     {        demo d1;              demo *dptr=&d1;              *dptr=1 ;               ++dptr;             *dptr=2;             ++dptr;             *dptr=3;          return 0;     } 

please explain why above code looks logical in fact not work in line 13 of code. log error:

no match 'operator=' in '*dptr=1'

 demo d1;  demo *dptr=&d1;   *dptr=1 ;    ++dptr;  dptr=2;  ++dptr;  dptr=3; 

dptr pointer pointing demo struct. so, *dptr = 1 same d1 = 1;, that's not valid.

plus, having pointer of type , doing ++ on pointer applies pointer arithmetic type, shoving pointer sizeof(demo), that's not want here. you'll need create int pointer casting it, using pointer read 3 fields

int* dptr=reinterpret_cast<int*>(&d1); 

padding can still ruin day though, however, since they're int's should fine.