invalid use of incomplete type 'struct MSG'

[MarekR22]

I would rather say that you have used forward declared structure MSG, so now in cpp you have to include header file with definition of this structure (it is not related at all with windows.h).

[stampede]

I would rather say that you have used forward declared structure MSG, so now in cpp you have to include header file with definition of this structure

Thats what I meant

it is not related at all with windows.h

MSG is defined in windows.h (winuser.h to be precise, but its included in windows.h) .

[libed]

Thank You guy's. Now its working fine.