The problem is that field names constructed due to wild-card
expansion done inside a stored procedure could point to freed
memory if the expansion was performed after the first call to
the stored procedure.

The problem was solved by patch for Bug#38691. The solution
was to allocate the database, table and field names in the
in the statement memory instead of table memory.

mysql-test/r/sp.result:
  Add test case result for Bug#38823
mysql-test/t/sp.test:
  Add test case for Bug#38823
sql/item.cc:
  Remark that this also impacts wildcard expansion inside SPs.