debug dynamically linked modules..

[Jesse Marlin <jesse dot marlin at intec dot us>]

Jack J writes:
 > Hi,
 > 
 > I would like to know how to debug using gdb
 > (set breakpoint on routine, etc.) a dynmically linked,
 > relocated code.
 > 
 > The platform is RH Linux 9.0. There is some
 > application
 > module compiled with -fPIC and -shared, and
 > -export-dynamic options.  
 > A global structure containing functions is exported by
 > the DLL module.
 > The problem: I would like to set breakpoint on one
 > of the (file static) functions contained in this
 > structure.
 > 
 > >From mainline code after call to dlsym(..) (to the
 > global structure), I try to set break point, and I
 > get error: "Function xxx not defined.".
 > 
 > I do 'info shared' on gdb and do see the file being
 > loaded. Also I do see that "-g" option to add
 > debug symbols in gcc.
 > 
 > Is there anything I am missing ? How does one 
 > normally use gdb in such scenario ?
 > 
 > Any tips, pointers/hints is appreciated.
 > 
 > Thanks,

One thing I do that is successful most of the time is place a
breakpoint on a file:line instead of on a function.  Try looking into
these:

br file:line       - place a breakpoint on a file and line number.
                     C-x SPC does this for you in (X)Emacs.

info shared        - shows which shared libraries are currently loaded.

(gdb) help sharedlibrary
Load shared object library symbols for files matching REGEXP.