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Coccinelle � ��FOSDEM/PGDay 2026 Developer Meeting��

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Bertrand Drouvot

Senior SDE at AWS

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Agenda

What is Coccinelle
How does that work?
Examples
What has been done so far
Other tools?
Plan
Questions

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What is Coccinelle

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“Coccinelle is a program matching and transformation engine which provides the language SmPL (Semantic Patch Language) for specifying desired matches and transformations in C code. Coccinelle was initially targeted towards performing collateral evolutions in Linux. Such evolutions comprise the changes that are needed in client code in response to evolutions in library APIs, and may include modifications such as renaming a function, adding a function argument whose value is somehow contextdependent, and reorganizing a data structure. Beyond collateral evolutions, Coccinelle is successfully used (by us and others) for finding and fixing bugs in systems code.”

From https://coccinelle.gitlabpages.inria.fr/website/

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What is Coccinelle

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“...a program matching and transformation engine for specifying desired matches and transformations in C code”:

arbitrary transformations of C code
refactoring
spotting bugs

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How does that work?

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From: https://inria.hal.science/inria-00123142/document

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Examples

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@@

type RT;

identifier fn != main;

@@

RT

fn()

{

...

}

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Examples

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@@

type RT;

identifier fn != main;

@@

RT

- fn()

{

...

}

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Examples

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@@

type RT;

identifier fn != main;

@@

RT

- fn()

+ fn(void)

{

...

}

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Examples

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@@

type RT;

identifier fn != main;

@@

RT

- fn();

+ fn(void);

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Examples

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@@

type T;

T E;

@@

- (T)

E

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Examples

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@@

type T = void*;

T x;

type T1;

T1 *E;

@@

x =

- (T)

E;

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So Far

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From: https://github.com/bdrouvot/coccinelle_on_pg

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And also

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Other tools?

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Not that I’m aware of
Compiler flags could help in some cases (-Wcast-qual, -Wstrict-prototypes…)
But the entire code tree is not always compiled…

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Plan

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Make it part of the code tree?
Set of dedicated scripts?
In upstream?
On some BF animals?

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Questions ��

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Thank you!