From d4b2c016344f04bf9f15e17ec0901ca09891da0f Mon Sep 17 00:00:00 2001
From: Pavel Avgustinov <pavel@semmle.com>
Date: Fri, 23 Nov 2018 14:22:44 +0000
Subject: [PATCH] Lift out intermediate helper predicate.

---
 .../Security/CWE/CWE-497/ExposedSystemData.ql | 20 +++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/cpp/ql/src/Security/CWE/CWE-497/ExposedSystemData.ql b/cpp/ql/src/Security/CWE/CWE-497/ExposedSystemData.ql
index ef804061e975..fc214b54f8ec 100644
--- a/cpp/ql/src/Security/CWE/CWE-497/ExposedSystemData.ql
+++ b/cpp/ql/src/Security/CWE/CWE-497/ExposedSystemData.ql
@@ -33,14 +33,7 @@ abstract class SystemData extends Element {
     result = getAnExpr() or
 
     // flow via global or member variable (conservative approximation)
-    exists(Variable var |
-      (
-        var.getAnAssignedValue() = getAnExprIndirect() or
-        var.getAnAccess() = getAnExprIndirect()
-      ) and
-      result = var.getAnAccess() and
-      not var instanceof LocalScopeVariable
-    ) or
+    result = getAnAffectedVar().getAnAccess() or
 
     // flow via stack variable
     definitionUsePair(_, getAnExprIndirect(), result) or
@@ -50,6 +43,17 @@ abstract class SystemData extends Element {
     // flow from assigned value to assignment expression
     result.(AssignExpr).getRValue() = getAnExprIndirect()
   }
+
+  /** Gets a global or member variable that may be affected by this system
+   * data (conservative approximation).
+   */
+  private Variable getAnAffectedVar() {
+    (
+      result.getAnAssignedValue() = this.getAnExprIndirect() or
+      result.getAnAccess() = this.getAnExprIndirect()
+    ) and
+    not result instanceof LocalScopeVariable
+  }
 }
 
 /**