On 9 June 2015 at 21:23, Ellis N. Thomas wrote: > Since my hardware remains the same from the time when I built gcc4.7.2 (only the > system software has been upgraded), is it possible to build "as" by specifying a target using > i386-apple-darwin13.4.0? I don't think so. You could try not using your gcc 4.7.2 (since it is configured and built for a different OS than the one you're running, which isn't likely to work well) and use the toolchain that comes with xtools instead. But I think the problem is that binutils just doesn't support your OS. You might just have to use the Apple linker and assembler that come with xtools.