> > So it would seem the answer is no, portable aliasing is not possible
> > in C++. Though I wonder if it should be (with a new language
> > feature).
>
> In practice, a union is exactly that, and I've not heard of a compiler
> which doesn't do the right thing. Given that it's explicitly legal in
> C11, I can't see any reason which C++ shouldn't simply adopt the same
> language.
I agree. But in the union case, you're copying bytes. If you don't perform
a copy, for example:
struct msg {
// ...
};
char *get_bytes();
msg *p = reinterpret_cast<msg*>(get_bytes());
if (p->i)
// ...
Then there can't be a portable way to do this, because there's hardware that
doesn't permit unaligned reads (e.g. where you'd get a SIGBUS). So I guess
I retract that "I wonder if" part :-)
Jay Haynberg
