So my starting point is generally an existing bug report, such as the last bug I attempted to fix:

• #509288 gnomad2: segfault on start up / vorbis comment headers

This bug was pretty simple to track down, and once I had added a couple of lines to the source to fix it creating the patch and reporting it was pretty simple.

The way I generally work is to download the source tree of the Debian package to my local system and work with it in-place until I think I've fixed the issue. I generally get the current sources to a package by running:

apt-get source "package"

Once I'm done fixing I'll want to create a patch. A patch is just a simple way of saying:

• open file foo.c
• Change "xxx" on line 12 to be "yyy".
• Add "blah blah" after line 25

Assuming I made my changes in the local source in /tmp/gnomad2-2.9.1 I'll move that somewhere safe, and download another copy of the unmodified source, so I can create a diff and ensure that I've got the change recorded correctly:

skx@gold:/tmp$ mv gnomad2-2.9.1 gnomad2-2.9.1.new
skx@gold:/tmp$ apt-get source gnomad2

Now I have two trees:

• /tmp/gnomad2-2.9.1.new - My modified, fixed, and updated directory.
• /tmp/gnomad2-2.9.1 - The current source in Debian's unstable branch.

Creating the patch just means running:

 diff --recursive \
      --ignore-space-change \
      --context \
 gnomad2-2.9.1 gnomad2-2.9.1.new/

This will output the diff to the console. You can save it to a file too by rusing tee:

 diff --recursive \
      --ignore-space-change \
      --context \
 gnomad2-2.9.1 gnomad2-2.9.1.new/  | tee /tmp/patch.diff

If the new directory isn't clean your patch will include things like:

Only in gnomad2-2.9.1.new/src: player.o
Only in gnomad2-2.9.1.new/src: playlists.o
Only in gnomad2-2.9.1.new/src: prefs.o
Only in gnomad2-2.9.1.new/src: tagfile.o
Only in gnomad2-2.9.1.new/src: util.o
Only in gnomad2-2.9.1.new/src: wavfile.o

Just edit those lines out of the diff.

So the next step is to submit that to the bug report. Simply mail "bugnumber@bugs.debian.org" (509288@bugs.debian.org in our example) including your patch in the mail. If all goes well you'll receive an auto-reply after a while.

Finally to make things neat you can manipulate the bug tracker by email by sending a mail :

To: control@bugs.debian.org
Subject: updates

tags 12344 + patch
end
stop
bored now

Here is one I sent earlier.

This will ensure that the bug is reported as having a patch present in it.

Job done.

In an ideal world the next time the package is uploaded to Debian the bug will be fixed, marked as closed, and the world will be a little happier.

In a non-ideal world your patch will sit in the bug tracker for years with no further comment. If that happens there is not too much you can do, except send reminders by email, or distract yourself with a nice curry.

Happily Debian maintainers really do seem to appreciate bug fixes, and I'd say it is rare that my fixes have been ignored. It happens, but not often enough to make me give up.