fix for bug #12744 (MYSQL_STMT operations cause seg fault after connection reset)

libmysql/libmysql.c:
  stmt->mysql could be 0x0 if the connection has failed between prepare and execute
  or any other operation. thus if the user decides to use mysql_stmt_reset()
  we should not segfault.
tests/mysql_client_test.c:
  test for bug #12744 (MYSQL_STMT operations cause seg fault after connection reset)

1 files changed, 6 insertions, 0 deletions

diff --git a/libmysql/libmysql.c b/libmysql/libmysql.c
index 921f042922a..498881aa947 100644
--- a/libmysql/libmysql.c
+++ b/libmysql/libmysql.c
@@ -4628,6 +4628,12 @@ my_bool STDCALL mysql_stmt_reset(MYSQL_STMT *stmt)
   /* If statement hasnt been prepared there is nothing to reset */
   if ((int) stmt->state < (int) MYSQL_STMT_PREPARE_DONE)
     DBUG_RETURN(0);
+  if (!stmt->mysql)
+  {
+    /* mysql can be reset in mysql_close called from mysql_reconnect */
+    set_stmt_error(stmt, CR_SERVER_LOST, unknown_sqlstate);
+    DBUG_RETURN(1);  
+  }
 
   mysql= stmt->mysql->last_used_con;
   int4store(buff, stmt->stmt_id);		/* Send stmt id to server */