This issue was originally raised in Bug 1715475:
The behavior of the Forte CC compiler changed with Forte 6.1 (Sunpro 5.2). Prior to Forte 6.1, the .c++ extension was not supported (and the compiler would reject it as an unknown file type). With 6.1 and later, the .c++ extension is supported. So should the Forte adapter bid on .c++ files (since they are currently supported) or not (since some compiler versions won't be able to handle them).
Initial response from carnold:
Maybe a half-hearted bid (something like DEFAULT_PROCESS_BID/2), so if no other compiler makes a full bid, then it will get a chance on the file. Better for a compiler that might be able to process it gets it than the linker (which gets all unbid files).