Sun 2003-08-03 22:31, Jasen Betts (3:640/1042) wrote to Bill Birrell:

 JB> I have a question: -  something that came up in the C++ echo recently

 JB> Given

 JB> typedef struct moo
 JB>   {
 JB>  int foo;
 JB>  char bar;
 JB>   } moo;


 JB> is   sizeof(moo) * 100   always the same as   sizeof( moo[100] )

moo[100] is not valid, but I think you mean:

moo amoo[100];

 JB> in other words does sizeof() include any slack space required for
 JB> alignment.

Structure padding is between structure members, not array elements, eg.

/* four byte alignment, four byte ints */

amoo =
{
  { /* amoo[0] */  424242, 'A'  /* followed by 3 bytes of padding */ },

  { /* amoo[1] */  848484, 'B'  /* followed by 3 bytes of padding */ }
}

But NOT:

amoo =
{
  { /* amoo[0] */  424242, 'A' },

  /* 3 bytes padding outside the struct - impossible */

  { /* amoo[1] */  848484, 'B' }

  /* another 3 bytes padding outside the struct - impossible */
}


I hope that makes sense...

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