Fixed BUG#13941: replace() string fuction behaves badly inside stored

                 procedure
  For some functions returning strings (like "replace" and "ifnull" - where
  val_str() is returning a pointer into one of the parameters) - we ended
  up with a dangling pointer after the new operator destroyed the reuse item
  in the eval function.
  A working, if not very elegant, solution is to simply copy the string in
  such cases.


mysql-test/r/sp.result:
  New test case for BUG#13941.
mysql-test/t/sp.test:
  New test case for BUG#13941.
sql/sp_head.cc:
  Copy the string when evaluating some string functions (e.g. "replace" and "ifnull")
  to avoid using a dangling pointer.

1 files changed, 15 insertions, 0 deletions

diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index 063c388702d..65e6a239242 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -293,6 +293,21 @@ sp_eval_func_item(THD *thd, Item **it_addr, enum enum_field_types type,
     if (it == reuse)
       DBUG_RETURN(it);
 
+    /*
+      For some functions, 's' is now pointing to an argument of the
+      function, which might be a local variable that it to be reused.
+      In this case, new(reuse, &rsize) below will call the destructor
+      and 's' ends up pointing to freed memory.
+      A somewhat ugly fix is to simply copy the string to our local one
+      (which is unused by most functions anyway), but only if 's' is
+      pointing somewhere else than to 'tmp' or 'it->str_value'.
+     */
+    if (reuse && s != &tmp && s != &it->str_value)
+    {
+      tmp.copy(s->c_ptr(), s->length(), it->collation.collation);
+      s= &tmp;
+    }
+
     CREATE_ON_CALLERS_ARENA(it= new(reuse, &rsize)
                             Item_string(it->collation.collation),
                             use_callers_arena, &backup_arena);