On 2025-01-07 Tu 2:44 PM, Mats Kindahl wrote:
I got some time over during the holidays, so I spent some of it
doing something I've been thinking about for a while.
For those of you that are not aware of it: Coccinelle is a tool for
pattern matching and text transformation for C code and can be used
for detection of problematic programming patterns and to make complex,
tree-wide patches easy. It is aware of the structure of C code and is
better suited to make complicated changes than what is possible using
normal text substitution tools like Sed and Perl.
Coccinelle have been successfully been used in the Linux project since
2008 and is now an established tool for Linux development and a large
number of semantic patches have been added to the source tree to
capture everything from generic issues (like eliminating the redundant
A in expressions like "!A || (A && B)") to more Linux-specific
problems like adding a missing call to kfree().
Although PostgreSQL is nowhere the size of the Linux kernel, it is
nevertheless of a significant size and would benefit from
incorporating Coccinelle into the development. I noticed it's been
used in a few cases way back (like 10 years back) to fix issues in the
PostgreSQL code, but I thought it might be useful to make it part of
normal development practice to, among other things:
- Identify and correct bugs in the source code both during development
and review.
- Make large-scale changes to the source tree to improve the code
based on new insights.
- Encode and enforce APIs by ensuring that function calls are used
correctly.
- Use improved coding patterns for more efficient code.
- Allow extensions to automatically update code for later PostgreSQL
versions.
To that end, I created a series of patches to show how it could be
used in the PostgreSQL tree. It is a lot easier to discuss concrete
code and I split it up into separate messages since that makes it
easier to discuss each individual patch. The series contains code to
make it easy to work with Coccinelle during development and reviews,
as well as examples of semantic patches that capture problems,
demonstrate how to make large-scale changes, how to enforce APIs, and
also improve some coding patterns.
This first patch contains the coccicheck.py script, which is a
re-implementation of the coccicheck script that the Linux kernel uses.
We cannot immediately use the coccicheck script since it is quite
closely tied to the Linux source code tree and we need to have
something that both supports autoconf and Meson. Since Python seems to
be used more and more in the tree, it seems to be the most natural
choice. (I have no strong opinion on what language to use, but think
it would be good to have something that is as platform-independent as
possible.)
The intention is that we should be able to use the Linux semantic
patches directly, so it supports the "Requires" and "Options"
keywords, which can be used to require a specific version of spatch(1)
and add options to the execution of that semantic patch, respectively.
Please don't start multiple threads like this. If you want to submit a
set of patches for a single feature, send them all as attachments in a
single email. Otherwise this just makes life hard for threading email
readers.
cheers
andrew
--
Andrew Dunstan
EDB: https://www.enterprisedb.com
