OK.
On Thu, Jan 25, 2018 at 10:26 AM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> Unnamed bitfields are not data members, so we should ignore them when
> counting the members or picking up members to initialize from, and
> also should ignore them in find_decomp_class_base, they can appear
> in various bases etc. and still there could be just one base containing
> direct non-static data members.
>
> The patch also fixes an issue I ran into on the testcase, when recursing
> from type in which we've found any direct non-static data members, we have
> ret set to that type and if the recursion doesn't find anything nor an
> error, it returns that ret rather than NULL. So, if t == ret, it just
> means it didn't find anything preventing return of ret to the caller.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2018-01-25 Jakub Jelinek <ja...@redhat.com>
>
> PR c++/84031
> * decl.c (find_decomp_class_base): Ignore unnamed bitfields. Ignore
> recursive calls that return ret.
> (cp_finish_decomp): Ignore unnamed bitfields.
>
> * g++.dg/cpp1z/decomp36.C: New test.
>
> --- gcc/cp/decl.c.jj 2018-01-24 17:18:42.376392255 +0100
> +++ gcc/cp/decl.c 2018-01-25 10:22:51.267122576 +0100
> @@ -7206,7 +7206,9 @@ find_decomp_class_base (location_t loc,
> {
> bool member_seen = false;
> for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
> - if (TREE_CODE (field) != FIELD_DECL || DECL_ARTIFICIAL (field))
> + if (TREE_CODE (field) != FIELD_DECL
> + || DECL_ARTIFICIAL (field)
> + || (DECL_C_BIT_FIELD (field) && !DECL_NAME (field)))
> continue;
> else if (ret)
> return type;
> @@ -7245,7 +7247,7 @@ find_decomp_class_base (location_t loc,
> tree t = find_decomp_class_base (loc, TREE_TYPE (base_binfo), ret);
> if (t == error_mark_node)
> return error_mark_node;
> - if (t != NULL_TREE)
> + if (t != NULL_TREE && t != ret)
> {
> if (ret == type)
> {
> @@ -7256,9 +7258,6 @@ find_decomp_class_base (location_t loc,
> }
> else if (orig_ret != NULL_TREE)
> return t;
> - else if (ret == t)
> - /* OK, found the same base along another path. We'll complain
> - in convert_to_base if it's ambiguous. */;
> else if (ret != NULL_TREE)
> {
> error_at (loc, "cannot decompose class type %qT: its base "
> @@ -7645,7 +7644,9 @@ cp_finish_decomp (tree decl, tree first,
> goto error_out;
> }
> for (tree field = TYPE_FIELDS (btype); field; field = TREE_CHAIN
> (field))
> - if (TREE_CODE (field) != FIELD_DECL || DECL_ARTIFICIAL (field))
> + if (TREE_CODE (field) != FIELD_DECL
> + || DECL_ARTIFICIAL (field)
> + || (DECL_C_BIT_FIELD (field) && !DECL_NAME (field)))
> continue;
> else
> eltscnt++;
> @@ -7660,7 +7661,9 @@ cp_finish_decomp (tree decl, tree first,
> }
> unsigned int i = 0;
> for (tree field = TYPE_FIELDS (btype); field; field = TREE_CHAIN
> (field))
> - if (TREE_CODE (field) != FIELD_DECL || DECL_ARTIFICIAL (field))
> + if (TREE_CODE (field) != FIELD_DECL
> + || DECL_ARTIFICIAL (field)
> + || (DECL_C_BIT_FIELD (field) && !DECL_NAME (field)))
> continue;
> else
> {
> --- gcc/testsuite/g++.dg/cpp1z/decomp36.C.jj 2018-01-25 10:25:23.900154509
> +0100
> +++ gcc/testsuite/g++.dg/cpp1z/decomp36.C 2018-01-25 10:25:15.996152860
> +0100
> @@ -0,0 +1,19 @@
> +// PR c++/84031
> +// { dg-do compile { target c++11 } }
> +// { dg-options "" }
> +
> +struct A { unsigned char : 1, a1 : 1, a2 : 2, : 1, a3 : 3; };
> +struct B { unsigned char : 1, : 7; };
> +struct C : B { constexpr C () : c1 (1), c2 (2), c3 (3) {} unsigned char : 1,
> c1 : 1, c2 : 2, : 1, c3 : 3; };
> +struct D : C { constexpr D () {} unsigned char : 1, : 7; };
> +
> +int
> +main ()
> +{
> + static constexpr A a { 1, 2, 3 };
> + const auto &[a1, a2, a3] = a; // { dg-warning "only
> available with" "" { target c++14_down } }
> + static_assert (a1 == 1 && a2 == 2 && a3 == 3, "");
> + static constexpr D d;
> + const auto &[d1, d2, d3] = d; // { dg-warning "only
> available with" "" { target c++14_down } }
> + static_assert (d1 == 1 && d2 == 2 && d3 == 3, "");
> +}
>
> Jakub
