Software debugging & effective bug reprting

Bug reporting,

• How to report an annoying feature and/or requesting a new feature in an application.

BE NICE! Talking to the developer and/or explaining why this feature is annoying or why this missing feature is important is a big plus "When I explained why the libwxgtk should be compiled with unicode/gtk2 support is important for Arabic language, The package maintainer got interested".

Debugging

• What is debugging, What's a debugger ?

The GNU debugger "gdb" Compiling applications with debugging symbols. -ggdb Removing the debugging symbols "strip -S" Obtaining a meaningful back trace. What's a back trace ? A list of steps by the application or a list of function calls lead to this situation. What is a core file ? What's a core dump ? Simply the memory of the application is being dumped to a file! Getting a useful back trace: we must compile with debugging symbols -ggdb from a core file where Attaching to another process where This is useful if the application is started via a script as openoffice and mozilla. Directly from gdb gdb foo r When the crash happens: go back to the terminal, You might need to press C-C where quit How to set break points. break file.c:#

Diffs and patches How to generate a unified diff: -N - Treat absent files as empty. -a - treat all files as text -u - Unified diff: -r - recursive How to exclude: How to apply a patch: --dry-run: Don't really modify files. -p#: strip # leading slashes from the files. How to remove "unapply" a patch: patch -R -R: Reverse.

CVS: Using my CVS server as an example. How to login. cvs -d:pserver:anonymous@uniball.dyndns.org:/var/lib/cvs login export CVSROOT=":pserver:anonymous@uniball.dyndns.org:/var/lib/cvs" cvs login How to checkout. cvs -d:pserver:anonymous@uniball.dyndns.org:/var/lib/cvs co projects/illigal or export CVSROOT=":pserver:anonymous@uniball.dyndns.org:/var/lib/cvs" cvs -z3 co projects/illigal How to update. cvs -z3 update How to request a diff

Demonstration of some crashes using my "illigal operation" application

• 1: Integer by zero (Random value) - Our code crashed.
• 6: strcpy crash! (Copy to a NULL pointer) - here our application caused an external function to crash.

Bugzilla:

• Bugzilla is one of the most widely spreaded bug tracking systems.
• Registration:
• Submitting a bug: OpenOffice IssueZilla.
  • We might have a wizard.
  • We might have the old complicated method.
  • Severety "If found": The effect of the bug on the user. Blocker: Non usable application. Critical: Crashes, causes loss of data, or is a severe memory leak. Major: Major loss of functionality
    • Priority "If found": The importance of the bug Immediate: Can't test or use the application or it's a security issue. Urgent: I can't use an important features of the application because of it. High: Something is broken but the application is still usable.
      • We have more bug tracking systems like gnats and the debian bug tracking system.

      strace & ltrace: trace system calls, signals & library calls

      Notes about interacting with the developers:

      • Generally be nice and remember that the guy is a volunteer.
      • Generally don't hijack a thread to include your patch, The patch is a trivial thing, This means that you attach it to the same thread if related, Otherwise start a new thread.
      • Most people prefere the unified diff format.
      • Try to stick to the coding standard used by the developer, This is not that important unless you are emailing a kernel patch ;-)
      • Don't feel angry if the developer tell you that the software is under the GPL and you can do whatever you can.
      • When reporting a bug, Report either a reproducable bug or the exact steps you followed with a backtrace if you can't reproduce it.

      Links: