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From: "qinzhao at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/108896] provide "element_count" attribute to give more
 context to __builtin_dynamic_object_size() and -fsanitize=bounds
Date: Wed, 08 Mar 2023 17:13:58 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108896

--- Comment #24 from qinzhao at gcc dot gnu.org ---
(In reply to Martin Uecker from comment #15)
>=20
> Yes, but that syntax would be intuitive which I would see
> as an advantage.

Yes, I agree.
>=20
> But I am not saying we shouldn't have the attribute first.

both the new attribute and the C's syntax extension might be needed at the =
same
time, I think.

1. Attribute might be better for changing the existing source code to make =
them
bound-checking friendly;
2. new code can use the C's syntax change, and hopefully this new syntax
extension can be made into next C language standard.

however, I think that both the new attribute and the new C syntax extension
should support the similar user interface. We might need to decide on this
first.

right now, the user interface we cannot agreed on is:

whether we should support the following nested annotation (either with
attribute or with the C syntax extension):

struct object {
        ...
        unsigned int items;
        ...
        struct inner {
                ...
                int flex[];
        };
} *ptr;


My opinion is: No, we should not support this, it will make the implementat=
ion
much more complicated both for attribute and for C syntax extension.=20

But I am not very sure on this yet.=20

Is the PLACEHOLDER_EXPR able to resolve this?=