Bob,

We actually found that even when run from a GUI, you need absolute 
paths for files sometimes.  The reason for this is that the user may 
have several projects, say one which builds a shared library, and one 
an app that uses it.  If debugging with the app project open, but not 
the shlib project, you can end up in  a frame with debug info referring 
to sources you don't know about.

For our purposes, we found it sufficient to add the dir path to the 
-stack-list-frames command.  Pretty much the only time we would not 
know where a file was was when gdb stopped, and we were fetching the 
stack.  You might also want it in the mi -break-insert command as well, 
if you want to map from breakpoints to files in you UI, dunno...

Anyway, we did this by adding a "frame_more_info" hook to the ordinary 
stack.c frame printing.  We haven't needed to add anything but the 
directory yet, but this does seem a place where more info might be 
useful in the future, so...

Anyway, if you are interested, here is a patch against the FSF TOT.  
It's hacked out of our sources - we haven't merged back from the 
interpreter branch yet, so there are a lot of differences between our 
sources & the FSF.  But this is pretty simple, and should work.