OMG Joe I think this worked! I didn't download your binary yet (I will), but I tried the 32 bit compile and it seems to assemble properly. Need to do a few more tests to confirm.
I asked around and it seems that the Macro and Repeat code in DASM has been buggy for some time now. Everyone's been using old binaries so they haven't noticed. Does anyone have source from earlier versions? I've tried compiling all the versions in the Sourceforge SVN and they all have the same problem... I don't have the time or patience to go dig in the code; would rather just find a build that runs.
I managed to get dasm compiled for Intel, but I'm having some sort of problem related to macros.
I get illegal character errors reported from the assembler for some, but not all instructions defined inside MAC/ENDM. Sometimes these lead to Segmentation fault: 11 errors.
Assembling without Macro definitions works fine.
I thought maybe this was a text encoding issue, but experimentation with both the input and the compilation seems to suggest that it's not.
Every time Apple upgrades Xcode, they change a bunch of stuff. The recent Xcode 4 update was a complete rewrite, including totally new project template and language syntax formats. Worse yet, Apple hasn't yet documented any of it. Effectively, they're turning Xcode into a Cocoa-only IDE, even if it technically still offers external build support.
Anyway, I've given up on Xcode entirely for anything but Mac/iOS programming, and moved over to TextMate, which is a great text editor that's a bit like emacs for the OS X gui. It's very customizable, so I spent some time this weekend building an Atari bundle and packaging that in with some VCS-specific build tools. The result is much easier, leaner, and more automated than it ever was in Xcode.
You can read more and download the installer here. Hope it'll be useful to some of you. Let me know if you have any problems, suggestions, etc.