On Thu, Jun 14, 2018 at 12:59:00PM -0400, Jason Merrill wrote:
> On Thu, Jun 14, 2018 at 12:51 PM, Marek Polacek <pola...@redhat.com> wrote:
> > On Mon, Jun 11, 2018 at 03:00:04PM -0400, Jason Merrill wrote:
> >> On Wed, Jun 6, 2018 at 5:18 PM, Marek Polacek <pola...@redhat.com> wrote:
> >> > We crash on this testcase containing a bogus attribute, because
> >> > cp_check_const_attributes accessed TREE_VALUE of a tree that happened to
> >> > be
> >> > expr_pack_expansion. Since here we're merely trying to evaluate
> >> > constexpr
> >> > arguments, I thought we could skip such bogus arguments.
> >>
> >> Hmm, attributes should always be a TREE_LIST, lots of places assume
> >> that. Why isn't the pack expansion wrapped in a TREE_LIST?
> >
> > I believe you did that on purpose. There pack comes from
> > cp_parser_std_attribute_list. We could wrap it into a TREE_LIST, but then
> > tsubst_attribute would have to be tweaked to handle the pack expansion
> > correctly.
>
> How so? tsubst_attribute expects to find a pack expansion in the
> TREE_VALUE of a TREE_LIST.
> And cp_parser_std_attribute_list puts the pack expansion in TREE_VALUE.
Exactly. But what tsubst_attribute gets currently is
<tree_list 0x7ffff001c280 tree_0
purpose <tree_list 0x7ffff0002f00
purpose <identifier_node 0x7fffefec7d80 gnu
normal local bindings <(nil)>>
value <identifier_node 0x7ffff0014f00 aligned
normal local bindings <(nil)>>>
value <expr_pack_expansion 0x7fffefeada20
arg:0 <tree_list 0x7ffff0002f50
value <alignof_expr 0x7ffff0015600 type <integer_type
0x7fffefecd7e0 long unsigned int>
readonly tree_0 arg:0 <template_type_parm 0x7ffff001a1f8 T>
alignas4.C:17:19 start: alignas4.C:17:19 finish:
alignas4.C:17:29>>
arg:1 <tree_list 0x7ffff0002f78 value <template_type_parm
0x7ffff001a1f8 T>>>>
so if I were to wrap the expr_pack_expansion in a TREE_LIST, I would have to
adjust
tsubst_attribute. But cp_check_const_attributes doesn't expect that the
TREE_VALUE
of the above is a non-list. Right?
Marek
