Hi guys,

Seems to be WPOBJECT.HH that is included, though the .H might be somewhere.

Recall that WPOBJECT.HH is the Direct-to-SOM header and WPOBJECT.H is the
classic SOM header.  They are mutually exclusive.

Just need to figure out which #include <os2.h> needs it. Is there a
simple way to get the preprocessor output?

Yes.  From the docs and help:

/Pc[+|-]
/Pc+: Run only the preprocessor against the source file
      and preserve comments during preprocessing.
/Pc-: Run only the preprocessor against the source file
      and do not preserve comments during preprocessing.
Default: /Pc-