On Tue, 2009-12-08 at 08:31 -0800, Roland Scheidegger wrote:
> Keith,
>
> I think there might be some slight issue with some of the changes in the
> drivers I did. In particular, I was under the impression it would be ok
> to do something like
> union a_union {
> int i;
> double d;
> };
> int f() {
> double d = 3.0;
> return ((union a_union *) &d)->i;
> };
> but in fact gcc manpage tells me it's not (the example is from gcc 4.4
> manpage) - this site told me this is ok, "casting through a union (2)"
> http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html,
> I guess it was considered ok in 2006 but not now (though I'm not sure
> why not)... I did that in some places because otherwise there's no way
> around assigning the value to the union and pass that around instead.
> Curiously though, despite the gcc manpage saying the code "might" not be
> ok, gcc doesn't warn about it in the places I used it.
> Anyway, I'm not sure it's worth bothering with this now, as drivers
> could be fixed up without any interface changes.
Is it a lot of extra work to fix? I wouldn't mind getting on top of
this once and for all.
Keith
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