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Add QLDoc explaining reverseRead

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Owen Mansel-Chan
2025-11-26 14:30:23 +00:00
parent 1d0fcd77d8
commit 9481fc9451
1 changed files with 7 additions and 0 deletions
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7
shared/dataflow/codeql/dataflow/internal/DataFlowImplConsistency.qll
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@@ -244,6 +244,13 @@ module MakeConsistency<
private predicate hasPost(Node n) { exists(PostUpdateNode post | post.getPreUpdateNode() = n) } private predicate hasPost(Node n) { exists(PostUpdateNode post | post.getPreUpdateNode() = n) }
/**
* Consider code like `a.b.f = source()`. There is flow from `source()` to
* `[post] a.b` (with an appropriate access path), but we also want there to
* be flow to `[post] a` (with an appropriate access path). The data flow
* library is able to infer this step because there is a read step from `a`
* to `a.b`, as long as the post-update node for `a` exists.
*/
query predicate reverseRead(Node n, string msg) { query predicate reverseRead(Node n, string msg) {
exists(Node n2 | readStep(n, _, n2) and hasPost(n2) and not hasPost(n)) and exists(Node n2 | readStep(n, _, n2) and hasPost(n2) and not hasPost(n)) and
not Input::reverseReadExclude(n) and not Input::reverseReadExclude(n) and