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

Martin Maechler maechler at stat.math.ethz.ch
Mon Jan 17 10:29:57 CET 2011

>>>>> Martin Maechler <maechler at stat.math.ethz.ch>
>>>>>     on Mon, 17 Jan 2011 10:15:17 +0100 writes:

>>>>> 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

oops! this should have been

      8) c   # [c]ontinue the 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

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