R devel - Jan 1998 - debugging dynamically loaded code

How can I debug code that I load at runtime?

Currently I do the following:

	load R.binary into gdb
	run
	load shared object code using dyn.load()
	quit the R process

from then on gdb seems to be smart enough such that the source code
of the .so file is available and I can set breakpoints etc.

however, when I restart the R process I get:

(gdb) break printing.c:7
Breakpoint 1 at 0x407af036: file printing.c, line 7.
(gdb) run
Starting program: /usr/local/lib/R/bin/R.binary
Cannot insert breakpoint 1:
Temporarily disabling shared library breakpoints:


i.e., all breakpoints are disbled and I cannot figure out how to
enable them again (even after inserting the .so object).

Am I missing anything?

Best,
Fritz
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The secret of symbolic debugging of dynamically loaded code is to
 - Call the debugger on the R executable.  Since I do this within
   emacs, I don't use the "R gdb" facility, I symbolically link
the
   R.binary file into the directory with my code and call the debugger 
   through M-x gdb.
 - Set the environment variables that the $RHOME/bin/R script would.
 - Start the R program.
 - At the R prompt, use dyn.load() to load your library.
 - Send an interrupt signal.  Inside of gud mode in emacs, I think you 
   send C-C C-C.  This will put you back to the debugger prompt.
 - Set the breakpoints in your code.
 - Continue execution of R by typing "signal 0<ret>".

As I mentioned above, I find it easiest to use the directory with my
code in it as the cwd and then make a symbolic link from that
directory to the R executable.  That way the .gdbinit can stay in the
directory with the code and be used to set up the environment and the
search paths for the source.

A sample .gdbinit would be
 set env RHOME /usr/lib/R
 set env R_PAPERSIZE letter
 set env R_PRINTCMD lpr
 dir /usr/lib/R/src/main
 dir /usr/lib/R/src/math
 dir /usr/lib/R/src/appl
 dir /usr/lib/R/src/unix

It is possible that those last lines could be written as
 dir $(RHOME)/src/main
instead.  I haven't tried it out.
-- 
Douglas Bates                            bates@stat.wisc.edu
Statistics Department                    608/262-2598
University of Wisconsin - Madison        http://www.stat.wisc.edu/~bates/
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