Thanks for responding. I didn't realize that what I wrote wasn't clear enough. I was reporting the fact that on Mac OS X, with gfortran set up as a compiler, it is necessary to redefine gfortran as a compiler on every invocation of C::B. What I mean is that gfortran disappears from the list of compilers. I wasn't asking for help with porting my program to the Mac. The only reason I mentioned the other OSs was to make it clear that I was seeing a behaviour on the Mac different from on W7 and Linux. As I've posted on the Help board, I'm willing to help to get this fixed, but my help will probably be limited to testing.
It occurs to me that possibly you are referring to my post on the development board, but I was referring to my previous post on this board.