[ESS] Interaction of ESS and gud-mode for gdb debugger

[Douglas Bates]

I'm not sure if this is an interaction of gud-mode and ESS but I am
unable to use gdb on compiled R code in the way that I could
previously.

The operating system is Ubuntu 9.10 on an amd64 desktop running what
is still called emacs-snapshot, even though it is now the released
version.  To be specific the emacs is

GNU Emacs 23.1.50.1 (x86_64-pc-linux-gnu, GTK+ Version 2.18.0) of
2009-09-27 on crested, modified by Debian

with ESS version 5.4.  The version of gdb is

GNU gdb (GDB) 7.0-ubuntu

I'm not sure what the version of gud-mode is but it would be the
version shipped with this emacs as I haven't altered it since the
initial install.

The way that I debug compiled code for R is to start R with ESS (i.e.
M-x R), load any packages that I need, then start gdb on the R
executable.  At that point I determine the process number of the R
process (e.g. M-! pgrep R) and in the gud-gdb buffer attach the
debugger to that process and set any necessary breakpoints.  In the
past the gud-gdb buffer would show that it was reading the symbols
from the various shared objects then it would give a prompt where I
could set breakpoints.  The *R* buffer would be frozen while this was
going on.  To return control of the R process you send the 0 signal
(i.e. sig 0) from the *gud-gdb* buffer.

I still get the output about reading the symbol tables but I no longer
get a prompt in the *gud-gdb*.  If I try to recover a prompt, say with
C-g, the R process in the *R* buffer is killed.

I imagine this change is documented somewhere and I could find out by
reading the gdb and perhaps the gud-mode documentation but right now I
would really prefer to spend my time debugging my code, instead of
learning about new capabilities.  Does anyone have any hints of where
to look or what to do?