On Dec 29, 2005, at 11:32 AM, Gabriel Dos Reis wrote:
I believe, but I'm not sure, that GCC is using type puning not
guaranteed to work (except "common sense" from "obvious model".)
I think the C family of language standards should think about the
issue and clarify their exact intent... I know C at least was kinda
inadequate from my perspective.
I guess we just have to wait till GCC is miscompiled (probably by
itself) to see whether the Middle End would cite chapter and verse :-)
Or, we can talk about it first. I'd prefer that we talk though the
corner cases instead of just assuming and putting them in. I'd argue
that we should enhance the manual with the corner cases so as to
guide the language standard into making the `right' decision.
In this area, I don't think we do anything unfriendly. What was your
concern?
I see we make use of
struct S { int first; } s;
&s == &s.first, and we upcast and down cast via pointer arithmetic,
and we assume we can change type when a pointer has the right value,
none of these run afoul of what gcc does afaik.
