Exchange - CancelOrder has no effect  Pending
The exchange provides means for the `trader` or `broker` to cancel the order. The `cancelOrder` method, however, only stores the hash of the canceled order in mapping but the mapping is never checked. It is therefore effectively impossible for a `trader` to cancel an order.\\n```\\nfunction cancelOrder(LibOrder.Order memory order) public {\\n    require(msg.sender == order.trader || msg.sender == order.broker, "invalid caller");\\n\\n    bytes32 orderHash = order.getOrderHash();\\n    cancelled[orderHash] = true;\\n\\n    emit Cancel(orderHash);\\n}\\n```\\n
`matchOrders*` or `validateOrderParam` should check if `cancelled[orderHash] == true` and abort fulfilling the order.\\nVerify the order params (Signature) before accepting it as canceled.
```\\nfunction cancelOrder(LibOrder.Order memory order) public {\\n    require(msg.sender == order.trader || msg.sender == order.broker, "invalid caller");\\n\\n    bytes32 orderHash = order.getOrderHash();\\n    cancelled[orderHash] = true;\\n\\n    emit Cancel(orderHash);\\n}\\n```\\n