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Merge pull request #20017 from jketema/final

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C++: Add dataflow predicate for checking if a node is the final value of a parameter
This commit is contained in:
Jeroen Ketema
2025-07-10 18:47:09 +02:00
committed by GitHub
parent 3a0def7848 96c379a076
commit 6d8e2f8231
3 changed files with 26 additions and 6 deletions
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4
cpp/ql/lib/change-notes/2025-07-10-final.md Normal file
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@@ -0,0 +1,4 @@
---
category: feature
---
* Added a `isFinalValueOfParameter` predicate to DataFlow::Node which holds when a dataflow node represents the final value of an output parameter of a function.

19
cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll
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@@ -488,6 +488,23 @@ class Node extends TIRDataFlowNode {
result = this.(IndirectParameterNode).getParameter()
}
/**
* Holds if this node represents the `indirectionIndex`'th indirection of
* the value of an output parameter `p` just before reaching the end of a function.
*/
predicate isFinalValueOfParameter(Parameter p, int indirectionIndex) {
exists(FinalParameterNode n | n = this |
p = n.getParameter() and
indirectionIndex = n.getIndirectionIndex()
)
}
/**
* Holds if this node represents the value of an output parameter `p`
* just before reaching the end of a function.
*/
predicate isFinalValueOfParameter(Parameter p) { this.isFinalValueOfParameter(p, _) }
/**
* Gets the variable corresponding to this node, if any. This can be used for
* modeling flow in and out of global variables.
@@ -1225,7 +1242,7 @@ import RawIndirectNodes
/**
* INTERNAL: do not use.
*
* A node representing the value of an update parameter
* A node representing the value of an output parameter
* just before reaching the end of a function.
*/
class FinalParameterNode extends Node, TFinalParameterNode {

9
cpp/ql/test/library-tests/dataflow/dataflow-tests/has-parameter-flow-out.ql
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@@ -24,10 +24,9 @@ module AstTest {
module IRTest {
private import semmle.code.cpp.ir.dataflow.DataFlow
private import semmle.code.cpp.ir.dataflow.internal.DataFlowUtil
private string stars(int k) {
k = [0 .. max(FinalParameterNode n | | n.getIndirectionIndex())] and
k = [0 .. max(DataFlow::Node n, int i | n.isFinalValueOfParameter(_, i) | i)] and
(if k = 0 then result = "" else result = "*" + stars(k - 1))
}
@@ -35,14 +34,14 @@ module IRTest {
string getARelevantTag() { result = "ir-def" }
predicate hasActualResult(Location location, string element, string tag, string value) {
exists(Function f, Parameter p, FinalParameterNode n |
exists(Function f, Parameter p, DataFlow::Node n, int i |
p.isNamed() and
n.getParameter() = p and
n.isFinalValueOfParameter(p, i) and
n.getFunction() = f and
location = f.getLocation() and
element = p.toString() and
tag = "ir-def" and
value = stars(n.getIndirectionIndex()) + p.getName()
value = stars(i) + p.getName()
)
}
}