compiler construction - C Structure Padding. Nested Structures - 


struct y{   int int_one;   int int_two;   void * pointer; }  struct x{     char char_one;     char char_two;     struct y y_structures[20];  }

the padding different on 32 , 64 bit machines. don't know why. far know padding should follows :

 0x0 char_one <br>  0x1 char_two <br>  0x4 y_structures[0].int_one <br>  0x8 y_structures[0].int_two <br>  0x12 y_structure[0].pointer <br>

the structure on 32 bit similar mentioned above on 64 bit machine difference between addresses of char_two , y_structures[0].int_one 7 bytes. think should 3 bytes because type aligned after char_two int of y_structures[0] , it's size 4 on both architectures. kindly help

the problem not int, it's pointer. pointer have size of 8 bytes on 64bit machines, therefore must start @ memory address mod 8.

0x0 char_one 0x1 char_two 0x8 y_structures[0].int_one 0x12 y_structures[0].int_two 0x16 y_structure[0].pointer 0x24 y_structures[1].int_one 0x28 y_structures[1].int_two 0x32 y_structure[1].pointer ...

so there must 6 padding bytes. not necessary on 32 bit machines, because there pointer have 4 byte.


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