XRoar will now operate as a GDB remote target when run with the -gdb option. This allows remote memory & register inspection/modification, breakpoints and some extended queries.
Some basic commands can be used to interact with it from any recent GDB, but it's better if GDB itself supports 6809 disassembly. Here is a git repository containing a clone of GDB, and the necessary additions in a separate branch. The current patch is against GDB 7.6.
$ git clone -b m6809-7.6 http://www.6809.org.uk/git/binutils-gdb.git
2016-05-30: This repository has changed because the source repository for GDB changed. It is now based on git://sourceware.org/git/binutils-gdb.git. Note that rebasing onto the current master will likely now fail, as GDB has changed architecturally somewhat since this branch was made.
Build & install with:
$ cd binutils-gdb $ ./configure --target=m6809 --disable-werror $ make $ make install
The resulting binary should be named m6809-gdb.
Note: --disable-werror is required on the configure line with more recent versions of gcc.
As building for Windows is a bit more of a chore, here's a pre-built executable: m6809-gdb.exe.
2014-04-21: Tormod Volden has pointed out an issue with long branch disassembly - hopefully fixed in the m6809-7.6 branch.
Now fire up XRoar with the -gdb option, and try:
$ m6809-gdb GNU gdb (GDB) 188.8.131.5231021-cvs [...] (gdb) target remote localhost:65520
Windows note: looks like localhost doesn't necessarily resolve by default on Windows. Try substituting 127.0.0.1 and add -gdb-ip 127.0.0.1 as an extra option to XRoar.
At the time of writing, DDD requires a patch to work with newer versions of GDB. The Debian build contains the patch, but for your convenience, I've copied it here.
Once built, DDD can be started using m6809-gdb as its debugger, and told to connect to XRoar on its default port:
$ ddd --debugger m6809-gdb --eval-command="target remote localhost:65520"
Please consult the documentation for GDB and DDD for more information on using these tools.