Hmm. Responding to my own email :-)
 
> g++ -c -I/usr/local/qt/include -I/usr/X11R6/include -fno-strength-reduce
> -Wno-unused -Wno-parentheses -o filename.o filename.c
> The includes may be unnecessary. Give it a spin. I'll try later, but I'm
in
> 'doze right now.

Yep. In fact the -fno-strength-reduce can be mostly dispensed with. So use:

g++ -c -O2 -Wno-unused -Wno-parentheses -o filename.o filename.c

Andrew