sp_instr_cursor_copy_struct::exec_core() created TYPELIBs on a wrong mem_root,
the one which is initialized in sp_head::execute(), this code:

  /* init per-instruction memroot */
  init_sql_alloc(&execute_mem_root, "per_instruction_memroot",
                 MEM_ROOT_BLOCK_SIZE, 0, MYF(0));

This memory root cleans up after every sp_instr_xxx executed, so later
sp_instr_cfetch::execute() tried to use already freed and trashed memory.

Changing sp_instr_cursor_copy_struct::exec_core() to call tmp.export_structure()
inside this block (not outside of it):
  thd->set_n_backup_active_arena(thd->spcont->callers_arena, &current_arena);
  ...
  thd->restore_active_arena(thd->spcont->callers_arena, &current_arena);

So now TYPELIBs created by sp_instr_cursor_copy_struct::exec_core() are
still available and valid when sp_instr_cfetch::execute() is called.
They are freed at the end of dispatch_command() corresponding to
the "CALL p1" statement.