On Mar 8, 2004, at 3:32 PM, Joe Buck wrote:
On Mon, Mar 08, 2004 at 11:57:00PM +0100, Gabriel Dos Reis wrote:
[#2] All declarations that refer to the same object or
function shall have compatible type; otherwise, the behavior
is undefined.
This would seem to suggest that in the situations where
non-transitive
behavior would otherwise result (for example, an incomplete struct
type is
compatible with two distinct and incompatible definitions of that
struct
type), and this matters (for the purpose of aliasing analysis, for
example), we have undefined behavior, so the compiler should be able
to
act as though this situation does not arise and assume transitivity.
Suppose we have 3 types T1, T2, Tcom such that T1 and T2
are not compatible, but Tcom is compatible with either T1 or T2.
Let's call the relationship between T1 and T2 "pseudo-compatible".
Then:
Tcom x;
T1 * p = (T1 *)&x;
T2 * q = (T2 *)&x;
foo()
{
T1 x = *p;
*q = ...
}