Merge pull request #13455 from owen-mc/dataflow/add-flowCheckNodeSpecific

Dataflow: add language-specific hook for breaking up big step relation

cpp/ql/lib/semmle/code/cpp/dataflow/internal/DataFlowImpl.qll

@@ -2021,7 +2021,8 @@ module Impl<FullStateConfigSig Config> {
       FlowCheckNode() {
         castNode(this.asNode()) or
         clearsContentCached(this.asNode(), _) or
-        expectsContentCached(this.asNode(), _)
+        expectsContentCached(this.asNode(), _) or
+        neverSkipInPathGraph(this.asNode())
       }
     }
 

cpp/ql/lib/semmle/code/cpp/dataflow/internal/DataFlowPrivate.qll

@@ -235,6 +235,12 @@ class CastNode extends Node {
   CastNode() { none() } // stub implementation
 }
 
+/**
+ * Holds if `n` should never be skipped over in the `PathGraph` and in path
+ * explanations.
+ */
+predicate neverSkipInPathGraph(Node n) { none() }
+
 class DataFlowCallable = Function;
 
 class DataFlowExpr = Expr;

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

@@ -2021,7 +2021,8 @@ module Impl<FullStateConfigSig Config> {
       FlowCheckNode() {
         castNode(this.asNode()) or
         clearsContentCached(this.asNode(), _) or
-        expectsContentCached(this.asNode(), _)
+        expectsContentCached(this.asNode(), _) or
+        neverSkipInPathGraph(this.asNode())
       }
     }
 

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

@@ -783,6 +783,12 @@ class CastNode extends Node {
   CastNode() { none() } // stub implementation
 }
 
+/**
+ * Holds if `n` should never be skipped over in the `PathGraph` and in path
+ * explanations.
+ */
+predicate neverSkipInPathGraph(Node n) { none() }
+
 /**
  * A function that may contain code or a variable that may contain itself. When
  * flow crosses from one _enclosing callable_ to another, the interprocedural