$Id$

How to debug GRASS modules and libraries with GNU gdb and DDD:

Re-compile the modules and libraries you want to debug with the -g switch to
the gcc compiler and without the -s switch to the linker:

1. Edit src/CMD/head/head and head.in for the above configuration

2. Run "make clean" from the sorce code root directory

3. Run "make" to recompile the code

Now you can start a grass5 session, start up the DDD debugger (ddd&) and
select the module to debug. The binary in $GISBASE/bin/ is not what you want
to look at, as this only switches between the interactive version and the
command line version of the module in many cases. The command line version
of the module is in $GISBASE/etc/bin/main/cmd, the interactive version in
$GISBASE/etc/bin/main/inter. For the "contributed" modules, the executable
is found in $GISBASE/etc/bin/contrib/inter or $GISBASE/etc/bin/contrib/cmd
respectively.

-- 
Andreas Lange, andreas.lange@rhein-main.de

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Debugging tools:

 gdb:     GNU debugger. GDB, the GNU Project debugger, allows you to see
          what is going on 'inside' another program while it executes -- 
          or what another program was doing at the moment it crashed.
          http://sources.redhat.com/gdb/

    Start gdb like this (after following above compile steps):
   gdb /usr/local/grass5/etc/bin/<module>
 
    r <grassflags> <grassparamters>
    
    The "where" command in gdb will give a traceback after a crash or break.

    Example:
    gdb /usr/local/grass5/etc/bin/cmd/r.in.tiff
    r in=map.tiff out=map
    where

 ddd:     GNU DDD is a graphical front-end for command-line debuggers such as
          GDB, DBX, WDB, Ladebug, JDB, XDB, the Perl debugger, or the Python
          debugger. Besides `usual'' front-end features such as viewing source
          texts, DDD has become famous through its interactive graphical data
          display, where data structures are displayed as graphs.
          http://www.gnu.org/software/ddd/ddd.html

    startup with module
    set break point
    run or use "next" step to go stepwise

 memprof: Profiling and leak detection. MemProf is a tool for profiling
          memory usage and finding memory leaks
          http://people.redhat.com/otaylor/memprof/