I think I might have figured this out, no thanks to the manual: wdclib -s shows me that all the C library functions are in the whatever.lib files, and if I add those to the linker then it finds them and complains that some other things are missing: __unlink, __close, __isatty, __write, __lseek.
Yea, there shouldn't be any disk related code supplied.
I can name 2 '816 computers that had a disk drive: the Apple //GS, and the SuperCPU thing for the C64.
So, how CAN there be any disk support code with the compiler. For what machines? It would be nice if there was sample code that could be used and ported, however.
stdio can exist, simply because it can work with a serial console, but even then I'd be surprised if there was any real support.
At best, they should have libraries that leverage the monitors built in to the W65C134SXB and W65C265SXB boards.
Otherwise, yea, you get to write the rest yourself.