[Libvir] What is the Difference Between virConnCopyLastError and virCopyLastError?

Hi, I am little confused about these api's such as virConnCopyLastError and virCopyLastError. Please correct my understanding. 1. virConnCopyLastError expects 2 parameter connection and virErrorPtr, This is used only after getting successful connection, If i call this without connection say it is NULL, I hope it will return -1 if no what will it return? 2. virCopyLastError expects on 1 parameter virErrorPtr, this can be used any time, even before getting connection, If it is No. Then when will i use virCopyLastError api? 3. If virConnectOpen/virConnectOpenReadOnly fails which api should be called to know the error code? Thanks & Regards --Ajish