Someone recently reported the same issue with Marlin and this fixed the issue
Tools > Board > Boards Manager… > Arduino AVR Boards(click on it) > select 1.6.11 from the “Select version” menu > Install
After installation completes click the “Close” button
The problem is caused by the new compiler version included with Arduino AVR Boards 1.6.12 and later, it is more picky about the bad code that someone wrote. You will need to avoid upgrading to any Arduino AVR Boards version above 1.6.11 until someone fixes the problem in the Marlin code.