On Tue, Aug 16, 2022 at 2:16 PM Nathan Sidwell <nat...@acm.org> wrote:
>
> On 8/15/22 10:03, Richard Biener wrote:
> > On Mon, Aug 15, 2022 at 3:29 PM Nathan Sidwell via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> >>
> >> On 8/2/22 10:44, Qing Zhao wrote:
> >>> Hi, Nathan,
> >>>
> >>> I am adding a new bitfield “decl_not_flexarray” in “tree_decl_common”
> >>> (gcc/tree-core.h) for the new gcc feature -fstrict-flex-arrays.
> >>>
> >>> ====
> >>> diff --git a/gcc/tree-core.h b/gcc/tree-core.h
> >>> index ea9f281f1cc..458c6e6ceea 100644
> >>> --- a/gcc/tree-core.h
> >>> +++ b/gcc/tree-core.h
> >>> @@ -1813,7 +1813,10 @@ struct GTY(()) tree_decl_common {
> >>> TYPE_WARN_IF_NOT_ALIGN. */
> >>> unsigned int warn_if_not_align : 6;
> >>>
> >>> - /* 14 bits unused. */
> >>> + /* In FIELD_DECL, this is DECL_NOT_FLEXARRAY. */
> >>> + unsigned int decl_not_flexarray : 1;
> >>
> >> Is it possible to invert the meaning here -- set the flag if it /IS/ a
> >> flexible array? negated flags can be confusing, and I see your patch
> >> sets it to '!is_flexible_array (...)' anyway?
> >
> > The issue is it's consumed by the middle-end but set by a single (or two)
> > frontends and the conservative setting is having the bit not set. That
> > works
> > nicely together with touching just the frontends that want stricter behavior
> > than currently ...
>
> Makes sense, but is the comment incomplete? I'm guessing this flag is
> for FIELD_DECLs /of array type/, and not just any old FIELD_DECL? After
> all a field of type int is not a flexible array, but presumably doesn't
> need this flag setting?
Yes, the docs should be more complete in tree.h on the actual DECL_NOT_FLEXARRAY
definition.
Richard.
> nathan
>
> --
> Nathan Sidwell
