backport of:

        ------------------------------------------------------------
        revno: 2617.81.1
        revision-id: tor.didriksen@sun.com-20090924061133-qo02zotz3yypmfpk
        parent: davi.arnaut@sun.com-20090923203724-tvz7x8dauzp686v7
        committer: Tor Didriksen <tor.didriksen@sun.com>
        branch nick: 6.0-codebase-bf-opt
        timestamp: Thu 2009-09-24 08:11:33 +0200
        message:
          Bug#47511 Segmentation fault during cleanup in sql_union (events_bugs.test)
          


sql/sql_lex.h:
  Ensure that fields used during cleanup() are always initialized by constructors.

sql/sql_lex.h

@@ -403,6 +403,8 @@ public:
 struct LEX;
 class st_select_lex;
 class st_select_lex_unit;
+
+
 class st_select_lex_node {
 protected:
   st_select_lex_node *next, **prev,   /* neighbor list */
@@ -440,8 +442,17 @@ public:
   { return (void*) alloc_root(mem_root, (uint) size); }
   static void operator delete(void *ptr,size_t size) { TRASH(ptr, size); }
   static void operator delete(void *ptr, MEM_ROOT *mem_root) {}
-  st_select_lex_node(): linkage(UNSPECIFIED_TYPE) {}
+
+  // Ensures that at least all members used during cleanup() are initialized.
+  st_select_lex_node()
+    : next(NULL), prev(NULL),
+      master(NULL), slave(NULL),
+      link_next(NULL), link_prev(NULL),
+      linkage(UNSPECIFIED_TYPE)
+  {
+  }
   virtual ~st_select_lex_node() {}
+
   inline st_select_lex_node* get_master() { return master; }
   virtual void init_query();
   virtual void init_select();
@@ -487,6 +498,8 @@ class select_result;
 class JOIN;
 class select_union;
 class Procedure;
+
+
 class st_select_lex_unit: public st_select_lex_node {
 protected:
   TABLE_LIST result_table_list;
@@ -498,6 +511,14 @@ protected:
   bool saved_error;
 
 public:
+  // Ensures that at least all members used during cleanup() are initialized.
+  st_select_lex_unit()
+    : union_result(NULL), table(NULL), result(NULL),
+      cleaned(false),
+      fake_select_lex(NULL)
+  {
+  }
+
   bool  prepared, // prepare phase already performed for UNION (unit)
     optimized, // optimize phase already performed for UNION (unit)
     executed, // already executed