1 files changed, 21 insertions, 2 deletions
diff --git a/src/select.c b/src/select.c
index a8547f811..9d4c15919 100644
--- a/src/select.c
+++ b/src/select.c
@@ -4611,6 +4611,25 @@ int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
 }
 
 /*
+** No-op routine for the parse-tree walker for SELECT statements.
+** subquery in the parser tree.
+*/
+int sqlite3SelectWalkNoop(Walker *NotUsed, Select *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return WRC_Continue;
+}
+
+#if SQLITE_DEBUG
+/*
+** Always assert.  This xSelectCallback2 implementation proves that the
+** xSelectCallback2 is never invoked.
+*/
+void sqlite3SelectWalkAssert2(Walker *NotUsed, Select *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  assert( 0 );
+}
+#endif
+/*
 ** This routine "expands" a SELECT statement and all of its subqueries.
 ** For additional information on what it means to "expand" a SELECT
 ** statement, see the comment on the selectExpand worker callback above.
@@ -4625,11 +4644,11 @@ int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
 */
 static void sqlite3SelectExpand(Parse *pParse, Select *pSelect){
   Walker w;
-  memset(&w, 0, sizeof(w));
   w.xExprCallback = sqlite3ExprWalkNoop;
   w.pParse = pParse;
   if( pParse->hasCompound ){
     w.xSelectCallback = convertCompoundSelectToSubquery;
+    w.xSelectCallback2 = 0;
     sqlite3WalkSelect(&w, pSelect);
   }
   w.xSelectCallback = selectExpander;
@@ -4689,7 +4708,7 @@ static void selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
 static void sqlite3SelectAddTypeInfo(Parse *pParse, Select *pSelect){
 #ifndef SQLITE_OMIT_SUBQUERY
   Walker w;
-  memset(&w, 0, sizeof(w));
+  w.xSelectCallback = sqlite3SelectWalkNoop;
   w.xSelectCallback2 = selectAddSubqueryTypeInfo;
   w.xExprCallback = sqlite3ExprWalkNoop;
   w.pParse = pParse;