C++: Add a testcase that needs indirect instruction/operand nodes.

cpp/ql/test/library-tests/dataflow/ir-barrier-guards/test.cpp

@@ -0,0 +1,9 @@
+bool checkArgument(int* x);
+
+void sink(int);
+
+void testCheckArgument(int* p) {
+  if (checkArgument(p)) {
+    sink(*p); // $ barrier MISSING:barrier=1
+  }
+}

cpp/ql/test/library-tests/dataflow/ir-barrier-guards/test.ql

@@ -0,0 +1,42 @@
+import cpp
+import semmle.code.cpp.dataflow.new.DataFlow
+import semmle.code.cpp.controlflow.IRGuards
+import utils.test.InlineExpectationsTest
+
+predicate instructionGuardChecks(IRGuardCondition gc, Instruction checked, boolean branch) {
+  exists(CallInstruction call |
+    call.getStaticCallTarget().hasName("checkArgument") and
+    checked = call.getAnArgument() and
+    gc.comparesEq(call.getAUse(), 0, false, any(BooleanValue bv | bv.getValue() = branch))
+  )
+}
+
+module BarrierGuard = DataFlow::InstructionBarrierGuard<instructionGuardChecks/3>;
+
+predicate indirectBarrierGuard(DataFlow::Node node, int indirectionIndex) {
+  node = BarrierGuard::getAnIndirectBarrierNode(indirectionIndex)
+}
+
+predicate barrierGuard(DataFlow::Node node) { node = BarrierGuard::getABarrierNode() }
+
+module Test implements TestSig {
+  string getARelevantTag() { result = "barrier" }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(DataFlow::Node node |
+      barrierGuard(node) and
+      value = ""
+      or
+      exists(int indirectionIndex |
+        indirectBarrierGuard(node, indirectionIndex) and
+        value = indirectionIndex.toString()
+      )
+    |
+      tag = "barrier" and
+      element = node.toString() and
+      location = node.getLocation()
+    )
+  }
+}
+
+import MakeTest<Test>