C++: Add more default predicates to product flow

Author: jketema

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/ProductFlow.qll

@@ -192,13 +192,13 @@ module ProductFlow {
      * Holds if data flow through `node` is prohibited through the first projection of the product
      * dataflow graph when the flow state is `state`.
      */
-    predicate isBarrier1(DataFlow::Node node, FlowState1 state);
+    default predicate isBarrier1(DataFlow::Node node, FlowState1 state) { none() }
 
     /**
      * Holds if data flow through `node` is prohibited through the second projection of the product
      * dataflow graph when the flow state is `state`.
      */
-    predicate isBarrier2(DataFlow::Node node, FlowState2 state);
+    default predicate isBarrier2(DataFlow::Node node, FlowState2 state) { none() }
 
     /**
      * Holds if data flow through `node` is prohibited through the first projection of the product
@@ -237,9 +237,11 @@ module ProductFlow {
      *
      * This step is only applicable in `state1` and updates the flow state to `state2`.
      */
-    predicate isAdditionalFlowStep1(
+    default predicate isAdditionalFlowStep1(
       DataFlow::Node node1, FlowState1 state1, DataFlow::Node node2, FlowState1 state2
-    );
+    ) {
+      none()
+    }
 
     /**
      * Holds if data may flow from `node1` to `node2` in addition to the normal data-flow steps in
@@ -253,9 +255,11 @@ module ProductFlow {
      *
      * This step is only applicable in `state1` and updates the flow state to `state2`.
      */
-    predicate isAdditionalFlowStep2(
+    default predicate isAdditionalFlowStep2(
       DataFlow::Node node1, FlowState2 state1, DataFlow::Node node2, FlowState2 state2
-    );
+    ) {
+      none()
+    }
 
     /**
      * Holds if data flow into `node` is prohibited in the first projection of the product

cpp/ql/src/Security/CWE/CWE-119/OverrunWriteProductFlow.ql

@@ -248,20 +248,10 @@ module StringSizeConfig implements ProductFlow::StateConfigSig {
     )
   }
 
-  predicate isBarrier1(DataFlow::Node node, FlowState1 state) { none() }
-
-  predicate isBarrier2(DataFlow::Node node, FlowState2 state) { none() }
-
   predicate isBarrierOut2(DataFlow::Node node) {
     node = any(DataFlow::SsaPhiNode phi).getAnInput(true)
   }
 
-  predicate isAdditionalFlowStep1(
-    DataFlow::Node node1, FlowState1 state1, DataFlow::Node node2, FlowState1 state2
-  ) {
-    none()
-  }
-
   predicate isAdditionalFlowStep2(
     DataFlow::Node node1, FlowState2 state1, DataFlow::Node node2, FlowState2 state2
   ) {

cpp/ql/src/experimental/Security/CWE/CWE-193/InvalidPointerDeref.ql

@@ -196,8 +196,6 @@ module AllocToInvalidPointerConfig implements ProductFlow::StateConfigSig {
     isSinkImpl(_, sink1, sink2, state2)
   }
 
-  predicate isBarrier1(DataFlow::Node node, FlowState1 state) { none() }
-
   predicate isBarrier2(DataFlow::Node node, FlowState2 state) {
     node = Barrier2::getABarrierNode(state)
   }
@@ -207,18 +205,6 @@ module AllocToInvalidPointerConfig implements ProductFlow::StateConfigSig {
   predicate isBarrierOut2(DataFlow::Node node) {
     node = any(DataFlow::SsaPhiNode phi).getAnInput(true)
   }
-
-  predicate isAdditionalFlowStep1(
-    DataFlow::Node node1, FlowState1 state1, DataFlow::Node node2, FlowState1 state2
-  ) {
-    none()
-  }
-
-  predicate isAdditionalFlowStep2(
-    DataFlow::Node node1, FlowState2 state1, DataFlow::Node node2, FlowState2 state2
-  ) {
-    none()
-  }
 }
 
 module AllocToInvalidPointerFlow = ProductFlow::GlobalWithState<AllocToInvalidPointerConfig>;