Say,

struct foo
{
int x;
double y;
/* etc. more variables defined */
short u;
char z;
} a;


Are the following true on all systems?

1) &a == &a.x
2) (&a.x < &a.y) && ( .. etc.. ) && ( &a.u < & a.z)


Are the following true if we change 'struct' to 'union' above, on all
systems?

3) &a == &a.x
4) &a.? == &a.? where ?s can be x, y, ..., u, or z (not necessarily
equal for both ?s)


Thank you for the .

Kenneth Bull wrote:
>
> struct foo {
> int x;
> double y;
> /* etc. more variables defined */
> short u;
> char z;
> } a;
>
> Are the following true on all systems?
>
> 1) &a == &a.x
> 2) (&a.x < &a.y) && ( .. etc.. ) && ( &a.u < & a.z)
>
> Are the following true if we change 'struct' to 'union' above, on all
> systems?
>
> 3) &a == &a.x
> 4) &a.? == &a.? where ?s can be x, y, ..., u, or z (not necessarily
> equal for both ?s)

Yes to all.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.

** Posted from http://www.teranews.com **

Kenneth Bull wrote:
> Say,
>
> struct foo
> {
> int x;
> double y;
> /* etc. more variables defined */
> short u;
> char z;
> } a;
>
>
> Are the following true on all systems?
>
> 1) &a == &a.x
> 2) (&a.x < &a.y) && ( .. etc.. ) && ( &a.u < & a.z)

No, but you're almost there.

Note that the pointer types don't match. Your expressions
violate constraints. It is true to say that...

(int *) &a == &a.x
&a == (struct foo *) &a.x

offsetof(struct foo, x) == 0
offsetof(struct foo, x) < offsetof(struct foo, y)
offsetof(struct foo, y) < offsetof(struct foo, u)
offsetof(struct foo, u) < offsetof(struct foo, z)

> Are the following true if we change 'struct' to 'union' above, on all
> systems?
>
> 3) &a == &a.x

(int *) &a == &a.x
&a == (union foo *) &a.x

> 4) &a.? == &a.? where ?s can be x, y, ..., u, or z (not necessarily
> equal for both ?s)

If the addresses are converted to void * or suitable type, they must
compare equal.

Note that it is not possible to take the address of bitfields.

--
Peter