Alright, I finally got all the dwarf stuff figured out. The debug_line section was actually built by the assembler, but the contents were malformed. The problem is that the assembler was trying to create a four-byte relocation record. This is a problem since for the tms9900 anything beyond a two byte address in a relocation record is meaningless.
I had implemented a workaround, but that was broken, and placed the relocation in the upper word. This made the actual section size and the size declared in the header disagree, as a result, no source line information ever gets parsed.
Realizing this problem was long and painful.
I spent some time studying the dwarf2 specification, but the debug_line section is implemented as bytecode for a virtual machine, so I wanted to avoid manual translation if I could. I tried to find something which could dump the strings section, but no such luck.
In the end I made a one-line program and stepped my way through the section using the dwarf specification and did some trial-and-error work to fix the broken header values.
Long story short, we're good now and I can finally prepare another release.