From f5113b1932d2dc1ea4e55fb3115cb56e33c6796b Mon Sep 17 00:00:00 2001
From: Mathias Vorreiter Pedersen <mathiasvp@github.com>
Date: Tue, 19 May 2026 15:39:32 +0100
Subject: [PATCH] C++: Fix internal SCC edges and accept test changes.

---
 .../semmle/code/cpp/ir/dataflow/internal/SsaImpl.qll   | 10 +++-------
 cpp/ql/test/library-tests/dataflow/certain/test.cpp    |  4 ++--
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImpl.qll b/cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImpl.qll
index 9702a325d5e..432261dfe27 100644
--- a/cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImpl.qll
+++ b/cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImpl.qll
@@ -1379,15 +1379,11 @@ class PhiNode extends Definition instanceof SsaImpl::PhiNode {
 
 private PhiNode getAnInput(PhiNode phi) { result = phi.getAnInput() }
 
-private predicate definitionCycle(PhiNode phi) { getAnInput+(phi) = phi }
-
-private predicate hasAnInput(PhiNode phi1, PhiNode phi2) {
-  definitionCycle(phi1) and
-  definitionCycle(phi2) and
-  getAnInput(phi1) = phi2
+private predicate sccEdge(PhiNode phi1, PhiNode phi2) {
+  getAnInput(phi1) = phi2 and getAnInput+(phi2) = phi1
 }
 
-private module PhiCycleEquivalence = QlBuiltins::EquivalenceRelation<PhiNode, hasAnInput/2>;
+private module PhiCycleEquivalence = QlBuiltins::EquivalenceRelation<PhiNode, sccEdge/2>;
 
 private PhiCycle getCycle(PhiNode phi) { result.getAPhiNode() = phi }
 
diff --git a/cpp/ql/test/library-tests/dataflow/certain/test.cpp b/cpp/ql/test/library-tests/dataflow/certain/test.cpp
index eece48c2ea3..029c329a36d 100644
--- a/cpp/ql/test/library-tests/dataflow/certain/test.cpp
+++ b/cpp/ql/test/library-tests/dataflow/certain/test.cpp
@@ -67,11 +67,11 @@ void test(int x, bool b1, bool b2) { // $ certain="SSA def(&x)" certain="SSA def
   int* p = &x; // $ certain="SSA def(&p)" certain="SSA def(p)" certain="SSA def(*p)" 
   int i = 0; // $ certain="SSA def(&i)" certain="SSA def(i)"
   int j = 0; // $ certain="SSA def(&j)" certain="SSA def(j)"
-  while (i < 10) { // $ certain="SSA phi(i)" uncertain="SSA phi(*p)"
+  while (i < 10) { // $ certain="SSA phi(i)" certain="SSA phi(*p)"
   if (b1) {
     *p = 0; // $ certain="SSA def(*p)" 
   }
-  ++i; // $ certain="SSA def(i)" uncertain="SSA phi(*p)"
+  ++i; // $ certain="SSA def(i)" certain="SSA phi(*p)"
   }
   while (j < 10) { // $ uncertain="SSA phi(*p)" certain="SSA phi(j)"
     if (b2) {