That's the default. It doesn't work because pointers are still 16 bits.
Something's still not right then. The H8/300 has 16 bit pointers and a
64k address space and all the processors in the family still support
that mode.
The problem is when a single object is more than 64k for the models
that have 16 bit pointers. No, they won't work on hardware, but we
can't even *compile* them because of the dwarf limitation, which means
all the other models can't support such large objects.
I.e. the 2-byte dwarf addresses for H8/300 prevent us from supporting
C++ on the larger H8/300SX processors.