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From: "qing.zhao at oracle dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107952] tree-object-size: inconsistent size
 for flexible arrays nested in structs
Date: Wed, 25 Jan 2023 16:40:14 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107952

--- Comment #15 from Qing Zhao <qing.zhao at oracle dot com> ---
> On Jan 25, 2023, at 11:12 AM, siddhesh at gcc dot gnu.org <gcc-bugzilla@g=
cc.gnu.org> wrote:
>>=20
>>> The first is handled by the function just fine,
>>=20
>> No, even the first case is not recognized by the current
>> =E2=80=9Carray_ref_flexible_size_p=E2=80=9D, it=E2=80=99s not been ident=
ified as a flexible array
>> right now.
>> Shall we include this case into =E2=80=9Carray_ref_flexible_size_p=E2=80=
=9D?  (It=E2=80=99s a GCC
>> extension).
>=20
> In the first case, array_ref_flexible_size_p recognizes S2.flex.data as h=
aving
> flexible size.  The tests in my patch[1] for this bug checks for this.
Oh, yes. That=E2=80=99s right.
>=20
> However, array_ref_flexible_size_p does not recognize S2.flex as having
> flexible size.  It might make sense to support that, i.e. any struct or u=
nion
> with the last element as a flex array should be recognized as having flex=
ible
> size.

Since S2.flex is not an =E2=80=9Carray_ref=E2=80=9D, it=E2=80=99s correct f=
or array_ref_fleixble_size_p
to return false for it, I think.=20
We might add a new utility routine to determine whether a ref to a struct or
union have flexible array?=