Re: Add counted_by attribute

On Wed, 29 Jul 2026 at 22:07, "Tristan Partin" <tristan(at)partin(dot)io> wrote:
> The counted_by[0] compiler attribute is fairly new. It was added in GCC
> 15 and Clang 18. It has been used fairly extensively in the Linux
> kernel[0].
>
> To summarize the benefits of the attribute:
>
> - Runtime bounds checking with -DFORTIFY_SOURCE=3 and -fsanitize-bounds
> - Accurate reporting of __builtin_dynamic_object_size()
>
> While we don't use __builtin_dynamic_object_size(), I think the runtime
> bounds checking improvements are easily worth the little bit of effort
> to add the attribute in various locations and review the code. I think
> it will improve things for buildfarm animals using ASan due to expanded
> coverage.
>
> Adding this attribute to the codebase was previously proposed back in
> 2024[1], but the thread never got any traction. I figured that I would
> try again, but bring some patches this time. I figured that I would
> start small, and then after people agree that it has value, I can look
> into adding the attribute in many more places.
>
> [0]: https://gcc.gnu.org/onlinedocs/gcc/Common-Attributes.html#index-counted_005fby
> [1]: https://people.kernel.org/gustavoars/how-to-use-the-new-counted_by-attribute-in-c-and-linux
> [2]: https://www.postgresql.org/message-id/ME3P282MB3166210CDE36BD485B703BF6B6C82@ME3P282MB3166.AUSP282.PROD.OUTLOOK.COM
>

+1 for this idea.

> --
> Tristan Partin
> PostgreSQL Contributors Team
> AWS (https://aws.amazon.com)

--
Regards,
Japin Li
ChengDu WenWu Information Technology Co., Ltd.