2016-06-24 23:09:20 +00:00
|
|
|
This directory provides examples of Coccinelle (http://coccinelle.lip6.fr/)
|
|
|
|
|
semantic patches that might be useful to developers.
|
2018-11-10 00:10:52 +00:00
|
|
|
|
|
|
|
|
There are two types of semantic patches:
|
|
|
|
|
|
|
|
|
|
* Using the semantic transformation to check for bad patterns in the code;
|
|
|
|
|
The target 'make coccicheck' is designed to check for these patterns and
|
|
|
|
|
it is expected that any resulting patch indicates a regression.
|
|
|
|
|
The patches resulting from 'make coccicheck' are small and infrequent,
|
|
|
|
|
so once they are found, they can be sent to the mailing list as per usual.
|
|
|
|
|
|
|
|
|
|
Example for introducing new patterns:
|
|
|
|
|
67947c34ae (convert "hashcmp() != 0" to "!hasheq()", 2018-08-28)
|
|
|
|
|
b84c783882 (fsck: s/++i > 1/i++/, 2018-10-24)
|
|
|
|
|
|
|
|
|
|
Example of fixes using this approach:
|
|
|
|
|
248f66ed8e (run-command: use strbuf_addstr() for adding a string to
|
|
|
|
|
a strbuf, 2018-03-25)
|
|
|
|
|
f919ffebed (Use MOVE_ARRAY, 2018-01-22)
|
|
|
|
|
|
|
|
|
|
These types of semantic patches are usually part of testing, c.f.
|
|
|
|
|
0860a7641b (travis-ci: fail if Coccinelle static analysis found something
|
|
|
|
|
to transform, 2018-07-23)
|
|
|
|
|
|
|
|
|
|
* Using semantic transformations in large scale refactorings throughout
|
|
|
|
|
the code base.
|
|
|
|
|
|
|
|
|
|
When applying the semantic patch into a real patch, sending it to the
|
|
|
|
|
mailing list in the usual way, such a patch would be expected to have a
|
|
|
|
|
lot of textual and semantic conflicts as such large scale refactorings
|
|
|
|
|
change function signatures that are used widely in the code base.
|
|
|
|
|
A textual conflict would arise if surrounding code near any call of such
|
|
|
|
|
function changes. A semantic conflict arises when other patch series in
|
|
|
|
|
flight introduce calls to such functions.
|
|
|
|
|
|
|
|
|
|
So to aid these large scale refactorings, semantic patches can be used.
|
|
|
|
|
However we do not want to store them in the same place as the checks for
|
|
|
|
|
bad patterns, as then automated builds would fail.
|
|
|
|
|
That is why semantic patches 'contrib/coccinelle/*.pending.cocci'
|
|
|
|
|
are ignored for checks, and can be applied using 'make coccicheck-pending'.
|
|
|
|
|
|
|
|
|
|
This allows to expose plans of pending large scale refactorings without
|
|
|
|
|
impacting the bad pattern checks.
|
