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Date: Wed, 29 Jul 2026 22:07:48 +0000
Message-Id: <DKBEBF32QLUA.3L2DJRPUYNKHZ@partin.io>
Subject: Add counted_by attribute
To: "pgsql-hackers" <pgsql-hackers@postgresql.org>
From: "Tristan Partin" <tristan@partin.io>
Archived-At: 
 <https://www.postgresql.org/message-id/DKBEBF32QLUA.3L2DJRPUYNKHZ%40partin.io>
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The counted_by[0] compiler attribute is fairly new. It was added in GCC=20
15 and Clang 18. It has been used fairly extensively in the Linux=20
kernel[0].

To summarize the benefits of the attribute:

- Runtime bounds checking with -DFORTIFY_SOURCE=3D3 and -fsanitize-bounds
- Accurate reporting of __builtin_dynamic_object_size()

While we don't use __builtin_dynamic_object_size(), I think the runtime=20
bounds checking improvements are easily worth the little bit of effort=20
to add the attribute in various locations and review the code. I think=20
it will improve things for buildfarm animals using ASan due to expanded=20
coverage.

Adding this attribute to the codebase was previously proposed back in=20
2024[1], but the thread never got any traction. I figured that I would=20
try again, but bring some patches this time. I figured that I would=20
start small, and then after people agree that it has value, I can look=20
into adding the attribute in many more places.

[0]: https://gcc.gnu.org/onlinedocs/gcc/Common-Attributes.html#index-counte=
d_005fby
[1]: https://people.kernel.org/gustavoars/how-to-use-the-new-counted_by-att=
ribute-in-c-and-linux
[2]: https://www.postgresql.org/message-id/ME3P282MB3166210CDE36BD485B703BF=
6B6C82@ME3P282MB3166.AUSP282.PROD.OUTLOOK.COM

--=20
Tristan Partin
PostgreSQL Contributors Team
AWS (https://aws.amazon.com)

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