C++: Use StackVariable in def-use libraries

Most of the implementation was already in terms of
`SemanticStackVariable`, so not much should have changed.

Author: jbj

cpp/ql/src/semmle/code/cpp/controlflow/DefinitionsAndUses.qll

@@ -1,5 +1,5 @@
 import cpp
-private import semmle.code.cpp.controlflow.LocalScopeVariableReachability
+private import semmle.code.cpp.controlflow.StackVariableReachability
 private import semmle.code.cpp.dataflow.EscapesTree
 
 /**
@@ -108,7 +108,7 @@ library class DefOrUse extends ControlFlowNodeBase {
     /*
      * Implementation detail: this predicate and its private auxiliary
      * predicates are instances of the more general predicates in
-     * LocalScopeVariableReachability.qll, and should be kept in sync.
+     * StackVariableReachability.qll, and should be kept in sync.
      *
      * Unfortunately, caching of abstract predicates does not work well, so the
      * predicates are duplicated for now.

cpp/ql/test/library-tests/defuse/definitionUsePairEquivalence.ql

@@ -1,24 +1,22 @@
 import cpp
-import semmle.code.cpp.controlflow.LocalScopeVariableReachability
+import semmle.code.cpp.controlflow.StackVariableReachability
 
-// Test that def/use algorithm is an instance of LocalScopeVariableReachability
-class MyDefOrUse extends LocalScopeVariableReachability {
+// Test that def/use algorithm is an instance of StackVariableReachability
+class MyDefOrUse extends StackVariableReachability {
   MyDefOrUse() { this = "MyDefUse" }
 
-  override predicate isSource(ControlFlowNode node, LocalScopeVariable v) { definition(v, node) }
+  override predicate isSource(ControlFlowNode node, StackVariable v) { definition(v, node) }
 
-  override predicate isSink(ControlFlowNode node, LocalScopeVariable v) { useOfVar(v, node) }
+  override predicate isSink(ControlFlowNode node, StackVariable v) { useOfVar(v, node) }
 
-  override predicate isBarrier(ControlFlowNode node, LocalScopeVariable v) {
-    definitionBarrier(v, node)
-  }
+  override predicate isBarrier(ControlFlowNode node, StackVariable v) { definitionBarrier(v, node) }
 }
 
 predicate equivalence() {
-  forall(LocalScopeVariable v, Expr first, Expr second | definitionUsePair(v, first, second) |
+  forall(StackVariable v, Expr first, Expr second | definitionUsePair(v, first, second) |
     exists(MyDefOrUse x | x.reaches(first, v, second))
   ) and
-  forall(LocalScopeVariable v, Expr first, Expr second |
+  forall(StackVariable v, Expr first, Expr second |
     exists(MyDefOrUse x | x.reaches(first, v, second))
   |
     definitionUsePair(v, first, second)

cpp/ql/test/library-tests/defuse/exprDefinition.ql

@@ -1,5 +1,5 @@
 import cpp
 
-from LocalScopeVariable v, ControlFlowNode def, Expr e
+from StackVariable v, ControlFlowNode def, Expr e
 where exprDefinition(v, def, e)
 select v, def, e

cpp/ql/test/library-tests/defuse/useOfVar.ql

@@ -1,5 +1,5 @@
 import cpp
 
-from LocalScopeVariable v, VariableAccess use
+from StackVariable v, VariableAccess use
 where useOfVar(v, use)
 select v, use

cpp/ql/test/library-tests/defuse/useOfVarActual.ql

@@ -1,9 +1,9 @@
 import cpp
 
-from LocalScopeVariable v, VariableAccess use
+from StackVariable v, VariableAccess use
 where
   useOfVarActual(v, use) and
   // Also check that `useOfVarActual` is a subset of `useOfVar`; if not
   // the query will not return any results
-  forall(LocalScopeVariable v0, VariableAccess use0 | useOfVarActual(v0, use0) | useOfVar(v0, use0))
+  forall(StackVariable v0, VariableAccess use0 | useOfVarActual(v0, use0) | useOfVar(v0, use0))
 select v, use

cpp/ql/test/library-tests/literal_locations/duplicate_literal_locations.ql

@@ -1,5 +1,5 @@
 import cpp
 
-from LocalScopeVariable v, ControlFlowNode def, Expr e
+from StackVariable v, ControlFlowNode def, Expr e
 where exprDefinition(v, def, e)
 select v, def, e