Add a (small) GDB tips section

[smontanaro]

This adds a GDB Tips section which describes two (I think) useful features when debugging the virtual machine, saving breakpoints to a file, and setting breakpoints at TARGET_<INST> labels.

[smontanaro]

Thanks for the suggestions @hugovk. I made a comment on one. Do you know how to edit it?

[hugovk]

Thanks for the suggestions @hugovk. I made a comment on one. Do you know how to edit it?

Yep, done!

[smontanaro]

This is kind of related to this (by now a bit stale) PR.

[erlend-aasland]

Some style nits and suggestions to make things slightly more succinct.

[smontanaro]

Hmmm... The rest of the document seems to differ a bit from what these suggestions indicate. For example, sections about GDB 6 and 7 use "gdb" instead of "GDB". Should I just go through the file and make all the style suggestions in one go?

[smontanaro]

Okay, I screwed up (again). I think I had accepted some earlier suggestions, but not incorporated them locally. Now when I try to push, I get:

% git push origin HEAD To github.com:smontanaro/devguide.git ! [rejected] HEAD -> gdb-tips (fetch first) error: failed to push some refs to 'github.com:smontanaro/devguide.git' hint: Updates were rejected because the remote contains work that you do hint: not have locally. This is usually caused by another repository pushing hint: to the same ref. You may want to first integrate the remote changes hint: (e.g., 'git pull ...') before pushing again. hint: See the 'Note about fast-forwards' in 'git push --help' for details. 

How do I fix this?

[hauntsaninja]

Maybe something like git pull origin --rebase $(git symbolic-ref --short HEAD), then git push origin HEAD

[erlend-aasland]

Hmmm... The rest of the document seems to differ a bit from what these suggestions indicate. For example, sections about GDB 6 and 7 use "gdb" instead of "GDB". Should I just go through the file and make all the style suggestions in one go?

IMO it is better to apply such a change in a separate issue/PR. For this PR, just follow the guidelines. There are some inconsistencies, for example regarding the indent level, but larger parts of the affected file does follow the existing guidelines regarding indent level.

[smontanaro]

Took a while, but I finally got things sync'd back up and accepted the various suggestions.

[erlend-aasland]

Thanks for this enhancement, Skip!