From 1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5 Mon Sep 17 00:00:00 2001 From: Vincent Ambo Date: Sat, 11 Jan 2020 23:36:56 +0000 Subject: Squashed 'third_party/git/' content from commit cb71568594 git-subtree-dir: third_party/git git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7 --- contrib/coccinelle/README | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 contrib/coccinelle/README (limited to 'contrib/coccinelle/README') diff --git a/contrib/coccinelle/README b/contrib/coccinelle/README new file mode 100644 index 000000000000..f0e80bd7f037 --- /dev/null +++ b/contrib/coccinelle/README @@ -0,0 +1,43 @@ +This directory provides examples of Coccinelle (http://coccinelle.lip6.fr/) +semantic patches that might be useful to developers. + +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. -- cgit 1.4.1