Manual-merge of patch for bug#11753738 from mysql-5.1 tree.

1 files changed, 16 insertions, 1 deletions

diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index a4010a587cc..557865c4830 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -2543,7 +2543,22 @@ void
 sp_head::restore_thd_mem_root(THD *thd)
 {
   DBUG_ENTER("sp_head::restore_thd_mem_root");
-  Item *flist= free_list;       // The old list
+
+  /*
+   In some cases our parser detects a syntax error and calls
+   LEX::cleanup_lex_after_parse_error() method only after
+   finishing parsing the whole routine. In such a situation
+   sp_head::restore_thd_mem_root() will be called twice - the
+   first time as part of normal parsing process and the second
+   time by cleanup_lex_after_parse_error().
+   To avoid ruining active arena/mem_root state in this case we
+   skip restoration of old arena/mem_root if this method has been
+   already called for this routine.
+  */
+  if (!m_thd)
+    DBUG_VOID_RETURN;
+
+  Item *flist= free_list;	// The old list
   set_query_arena(thd);         // Get new free_list and mem_root
   state= STMT_INITIALIZED_FOR_SP;