🚀 go-pugleaf

> |  struct {
> |    char a[3];
> |    char b[2];
> |  } x;
> 
> The Standard allows arbitrary padding between fields and after the
> last field.

Not quite; it allows padding so that the members are correctly aligned
for their types.  It does not say anything about padding being permitted
for any other reasons, and my interpretation is that it isn't.

> You cannot rely on the offset of member 'b' being the
> same on different implementations.

This conclusion is correct, though; there's nothing to say that array-of-
character types have to have the alignment requirement as character types.
For example, the compiler is at liberty to force all arrays of char to
begin on a 4-byte boundary, and therefore insert 1 byte between a and b.
-- 
Mark Brader	  "I'm not a lawyer, but I'm pedantic and that's just as good."
utzoo!sq!msb, msb@sq.com				       -- D Gary Grady

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