OK.
On Mon, Jan 29, 2018 at 1:12 PM, Marek Polacek <pola...@redhat.com> wrote:
> The crash here is caused by size_binop_loc getting operands of different
> types:
> sizetype and ssizetype. Fixed by performing the computation in offset_int,
> much as we do in fold_indirect_ref_1 (fixed in middle-end/81695).
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2018-01-29 Marek Polacek <pola...@redhat.com>
>
> PR c++/83996
> * constexpr.c (cxx_fold_indirect_ref): Compute ((foo *)&fooarray)[1]
> => fooarray[1] in offset_int.
>
> * g++.dg/ext/pr83996.C: New test.
>
> diff --git gcc/cp/constexpr.c gcc/cp/constexpr.c
> index 4d2ee4a28fc..0a1944f6dad 100644
> --- gcc/cp/constexpr.c
> +++ gcc/cp/constexpr.c
> @@ -3143,11 +3143,17 @@ cxx_fold_indirect_ref (location_t loc, tree type,
> tree op0, bool *empty_base)
> tree min_val = size_zero_node;
> if (type_domain && TYPE_MIN_VALUE (type_domain))
> min_val = TYPE_MIN_VALUE (type_domain);
> - op01 = size_binop_loc (loc, EXACT_DIV_EXPR, op01,
> - TYPE_SIZE_UNIT (type));
> - op01 = size_binop_loc (loc, PLUS_EXPR, op01, min_val);
> - return build4_loc (loc, ARRAY_REF, type, op00, op01,
> - NULL_TREE, NULL_TREE);
> + offset_int off = wi::to_offset (op01);
> + offset_int el_sz = wi::to_offset (TYPE_SIZE_UNIT (type));
> + offset_int remainder;
> + off = wi::divmod_trunc (off, el_sz, SIGNED, &remainder);
> + if (remainder == 0 && TREE_CODE (min_val) == INTEGER_CST)
> + {
> + off = off + wi::to_offset (min_val);
> + op01 = wide_int_to_tree (sizetype, off);
> + return build4_loc (loc, ARRAY_REF, type, op00, op01,
> + NULL_TREE, NULL_TREE);
> + }
> }
> /* Also handle conversion to an empty base class, which
> is represented with a NOP_EXPR. */
> diff --git gcc/testsuite/g++.dg/ext/pr83996.C
> gcc/testsuite/g++.dg/ext/pr83996.C
> index e69de29bb2d..e663d728349 100644
> --- gcc/testsuite/g++.dg/ext/pr83996.C
> +++ gcc/testsuite/g++.dg/ext/pr83996.C
> @@ -0,0 +1,11 @@
> +// PR c++/83996
> +// { dg-do compile }
> +// { dg-options "" }
> +
> +int z[] = { };
> +
> +int
> +main (void)
> +{
> + __builtin_printf ("%d\n", *(z + 1));
> +}
>
> Marek
