(Command-line option to suppress warning: -w-pck) 

This warning message is issued when the structure alignment is different after including a file than it was before including that file.  

The intention is to warn you about cases where an include file changes structure packing, but by mistake doesn't restore the original setting at the end. If this is intentional, you can give a #pragma nopackwarning directive at the end of an include file to disable the warning for this file.  

The warning can be disabled altogether by #pragma warn -pck.