[ESS] Running gdb under emacs 23.1 and attaching to an ess-based R process

[Martin Maechler]

>>>>> Douglas Bates <bates at stat.wisc.edu>
>>>>>     on Wed, 12 Jan 2011 15:24:52 -0600 writes:

    > In the past I had a wonderfully effective way of getting
    > at compiled code in an R package with gdb.  I would start
    > R with ESS (M-x R) and load the package.  Then I would
    > start gdb on the binary (M-x gdb <RET>
    > /usr/lib/R/bin/exec/R), find the process number of the R
    > process (M-!  pgrep R) and attach gdb to that
    > already-running process.  I would interrupt R, set
    > breakpoints and then send the sig 0 signal.

    > Now I am running emacs 23.1 (which, for some reason, is
    > still called emacs-snapshot in Ubuntu) with enhanced
    > support for gdb.  M-x gdb ends up opening multiple windows
    > and I can't get things straightened out to have the input
    > and output from the attached process associated with the
    > *R* buffer.

    > Has anyone been able to run the gdb/R combination with
    > emacs support?  My problem is that I am so accustomed to
    > the emacs/ess key sequences that I feel crippled when
    > trying to run R in any other environment :-)

As a workaround :

I've been using the much less sophisticated scheme,
with the advantage that it has always worked on all versions of
Emacs and R ..


1)  C-u M-x R  [Enter] -d gdb [Enter]    # starting R with gdb in a *R* buffer
2)  C-g {to interrupt Emacs waiting for R's prompt .. ouch!}
3)  C-x b *R ... to manually switch the *R..* buffer in which
    you now have a prompt '(gdb) '
4) r                 # start running R
5) require(...) ...  ## load all R packages and R code I need
6) C-c C-c         (interrupt): break out of R back into gdb
7) br ...             ## setting breakpoints in gdb for C code

8) r   # back to running R
9) in R, call the code that will get into calling the break
   pointed C code
10) work in the *R* buffer entering gdb commands
11) "goto 8)"


This allows to use ESS (Emacs R interface), almost normally,
but of course the disadvantage is that this does not make any
use of the Emacs gdb interface.

We (ESS developers) could make steps 1) -- 3) more easy, notably
allowing ESS to also detect "(gdb) " as an R prompt which should
basically eliminate '2)' and '3)'.

I agree that the real solution should make Doug's original way
workable again, but we need someone (not me) tackle that...

Martin