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| -rw-r--r-- | contrib/coccinelle/README | 40 |
1 files changed, 36 insertions, 4 deletions
diff --git a/contrib/coccinelle/README b/contrib/coccinelle/README index d1daa1f626..055ad0e06a 100644 --- a/contrib/coccinelle/README +++ b/contrib/coccinelle/README @@ -1,7 +1,9 @@ -This directory provides examples of Coccinelle (http://coccinelle.lip6.fr/) -semantic patches that might be useful to developers. += coccinelle -There are two types of semantic patches: +This directory provides Coccinelle (http://coccinelle.lip6.fr/) semantic patches +that might be useful to developers. + +== 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 @@ -42,7 +44,7 @@ There are two types of semantic patches: This allows to expose plans of pending large scale refactorings without impacting the bad pattern checks. -Git-specific tips & things to know about how we run "spatch": +== Git-specific tips & things to know about how we run "spatch": * The "make coccicheck" will piggy-back on "COMPUTE_HEADER_DEPENDENCIES". If you've built a given object file @@ -90,3 +92,33 @@ Git-specific tips & things to know about how we run "spatch": The absolute times will differ for you, but the relative speedup from caching should be on that order. + +== Authoring and reviewing coccinelle changes + +* When a .cocci is made, both the Git changes and .cocci file should be + reviewed. When reviewing such a change, do your best to understand the .cocci + changes (e.g. by asking the author to explain the change) and be explicit + about your understanding of the changes. This helps us decide whether input + from coccinelle experts is needed or not. If you aren't sure of the cocci + changes, indicate what changes you actively endorse and leave an Acked-by + (instead of Reviewed-by). + +* Authors should consider that reviewers may not be coccinelle experts, thus the + the .cocci changes may not be self-evident. A plain text description of the + changes is strongly encouraged, especially when using more esoteric features + of the language. + +* .cocci rules should target only the problem it is trying to solve; "collateral + damage" is not allowed. Reviewers should look out and flag overly-broad rules. + +* Consider the cost-benefit ratio of .cocci changes. In particular, consider the + effect on the runtime of "make coccicheck", and how often your .cocci check + will catch something valuable. As a rule of thumb, rules that can bail early + if a file doesn't have a particular token will have a small impact on runtime, + and vice-versa. + +* .cocci files used for refactoring should be temporarily kept in-tree to aid + the refactoring of out-of-tree code (e.g. in-flight topics). Periodically + evaluate the cost-benefit ratio to determine when the file should be removed. + For example, consider how many out-of-tree users are left and how much this + slows down "make coccicheck". |