Take schema\FIX42.xml and remove all messages except for session and market data (see attached FIX42.xml file for result). This is possible if you want to just subscribe to market data and not place orders. In this case fileds ##1-6 will become unused and f8c will try to remove them. Unfortunately this results in invalid my_types.cpp (see attached file), in particular fldpairs array is generated incorrectly (see leading comma):
A workaround for this is to manually remove fields ##1-6 from <fields/> tag in FIX42.xml.
Windows 7 Pro, SP 1. Microsoft Visual Studio 2015, Update 3.