C++: Avoid a CP between 'getExpr(node)' and 'this' in 'LoopWithAlloca'.

Author: MathiasVP

cpp/ql/src/Likely Bugs/Memory Management/AllocaInLoop.ql

@@ -37,6 +37,19 @@ class AllocaCall extends FunctionCall {
   }
 }
 
+/**
+ * Gets an expression associated with a dataflow node.
+ */
+private Expr getExpr(DataFlow::Node node) {
+  result = node.asInstruction().getAst()
+  or
+  result = node.asOperand().getUse().getAst()
+  or
+  result = node.(DataFlow::RawIndirectInstruction).getInstruction().getAst()
+  or
+  result = node.(DataFlow::RawIndirectOperand).getOperand().getUse().getAst()
+}
+
 /**
  * A loop that contains an `alloca` call.
  */
@@ -185,19 +198,6 @@ class LoopWithAlloca extends Stmt {
     not this.conditionReachesWithoutUpdate(var, this.(Loop).getCondition())
   }
 
-  /**
-   * Gets an expression associated with a dataflow node.
-   */
-  private Expr getExpr(DataFlow::Node node) {
-    result = node.asInstruction().getAst()
-    or
-    result = node.asOperand().getUse().getAst()
-    or
-    result = node.(DataFlow::RawIndirectInstruction).getInstruction().getAst()
-    or
-    result = node.(DataFlow::RawIndirectOperand).getOperand().getUse().getAst()
-  }
-
   /**
    * Gets a definition that may be the most recent definition of the
    * controlling variable `var` before this loop.
@@ -210,7 +210,7 @@ class LoopWithAlloca extends Stmt {
       // Phi nodes will be preceded by nodes that represent actual definitions
       not result instanceof DataFlow::SsaPhiNode and
       // A source is outside the loop if it's not inside the loop
-      not exists(Expr e | e = this.getExpr(result) | this = getAnEnclosingLoopOfExpr(e))
+      not exists(Expr e | e = getExpr(result) | this = getAnEnclosingLoopOfExpr(e))
     )
   }
 
@@ -221,9 +221,9 @@ class LoopWithAlloca extends Stmt {
   private int getAControllingVarInitialValue(Variable var, DataFlow::Node source) {
     source = this.getAPrecedingDef(var) and
     (
-      result = this.getExpr(source).getValue().toInt()
+      result = getExpr(source).getValue().toInt()
       or
-      result = this.getExpr(source).(Assignment).getRValue().getValue().toInt()
+      result = getExpr(source).(Assignment).getRValue().getValue().toInt()
     )
   }