On Thu, Mar 19, 2015 at 07:13:47PM +0100, Marek Polacek wrote:
> On Thu, Mar 19, 2015 at 07:05:36PM +0100, Jakub Jelinek wrote:
> > I believe cxx_fold_indirect_ref result is not passed through to the
> > middle-end, unless it can be folded into a constant.
> >
> > Though, a question is if we do (or, if we don't and should) reject say
> > constexpr char s[] = "abc";
> > constexpr int j = 4;
> > constexpr char c = *(&s[j] - 2);
> > because there was out of bound access in there.
>
> That is rejected even with my patch with:
> error: overflow in constant expression [-fpermissive]
> and without the patch:
> error: ‘*((& s[4]) + 18446744073709551614u)’ is not a constant expression
> (a valid constexpr can't have UB).
But s/j = 4/j = 3/ should be valid, don't we reject even that?
I mean, isn't the rejection because we fold the - 2 early into sizetype
(unsigned) + -2UL?
Jakub
