[TUHS] v6 debugging

All, I'm finally returning to my study of v6 after digging a bit further into assembly language and "other" pdp-11 operating systems. I even managed to get hello, world working in assembly in v6 and interestingly enough, I actually see how it works... for the most part :). Mini-note here: http://decuser.blogspot.com/2016/01/hello-world-in-assembly-on-research.html My question for y'all today is as follows (asked previously with a much larger gap in understanding): How did folks debug assembly routines in Unix v6, back in the day? I realize that most folks didn't do assembly, but some did and I'm curious what their approach might have been. After having worked with RT-11 for a bit, I can see how I might develop using RT-11 and then "port" a program across, but that seems less than ideal. Here is my short list of missing features as I see them: 1. No listing file/cross reference list created by as. 2. No map file created by ld. 3. No debugger that I can find. 4. This is not a missing feature, but it deserves inclusion in the list, the command as has possibly the most terse error messages I have ever seen - B 12? Really? Thankfully, the awesome man command comes to the rescue with the list of error codes. My workarounds include using OD to view the generated machine code and adding mesg calls. Thoughts? Will