On Fri, Mar 20, 2015 at 10:53:50AM -0400, Jason Merrill wrote:
> On 03/19/2015 02:05 PM, Jakub Jelinek wrote:
> >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.
>
> I don't see an out-of-bound access in this example; taking the address of
> one-past-the-end is OK as long as you don't try to access through it.
It is taking address of two past the end though - &s[3] is fine, sure.
But &s[4] is invalid already.
> >Unfortunately we reject even that (regardless the patch), and yeah, it's
> >because of how POINTER_PLUS_EXPR uses sizetype as a type of the second
> >operand.
>
> This seems like something to fix in this patch.
>
> >+ tree t = fold_convert_loc (loc, TREE_TYPE (op01),
> >+ TREE_OPERAND (op00, 1));
> >+ t = size_binop_loc (loc, PLUS_EXPR, op01, t);
>
> This seems to be assuming that the elements are size 1.
Jakub
