Re: [tlug] Portability of Misaligned Data Access . . . . . . .

["Stephen J. Turnbull" <stephen@example.com>]

>>>>> "Joe" == Joe Larabell <fred62@???> writes:

    Joe> In the interest of pedantic portability, C already has a
    Joe> methor for ensuring that data which must be accessed in
    Joe> different ways is aligned correctly:

union u
{
  char     as_str[ sizeof( double ) + 1 ];
  struct s
  {
    double as_dbl;
    char   a_null;
  };
};

    Joe> As confusing as this looks, this should line the double up
    Joe> with the first 'n' bytes of the string and match the sizes of
    Joe> the two representations on any mahine.

Yeah, but it's a *lot* uglier than that.  Remember the header!  What
you really need is something like:

union {
  struct {
    char pad[6];
    char input[10];
  } namadata;
  struct {
    union {
      struct {
        char pad[6];
        char header[2];
        } prefix;
      double align;
    }
    double payload;
  } yakidata;
} do_you_really_expect_to_pull_this_off_interrobang;

and even then there's no guarantee you'll get a packed structure, or
even that sizeof(char) == 1.

I really have to wonder if the format produced by ibrd() really is

struct {
  char header[2];
  double payload;
}

and not

struct {
  char header[2];
  char number[8];
}

The former looks like an exceptionally nasty and pointless form of
data torture.

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