Thursday, 18 June 2009

gdb trick

I had a problem with gnome-bluetooth's wizard, a couple of days ago, that I couldn't reproduce when running under gdb. Turns out that I'm too slow at typing or something, and the problem was a race (though a slow one).

There's a few tips and tricks in this class material. The one I was interested in was:
(gdb) break foobar_new
(gdb) commands
thread apply all bt
continue
end

Then, every time you hit that break point, you'll get a backtrace, and the program will continue. I fixed that bug I saw :)
at

4 comments:

  1. Luis Villa18 June 2009 at 18:31

    Clearly you never had to debug evolution. thread apply all bt is burned into my brain, still, getting on 8 years later...

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  2. Bastien Nocera18 June 2009 at 19:03

    I know thread apply all bt very well, the trick here is the fact that you can get the backtrace for a breakpoint without stopping the software.

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  3. Anonymous18 June 2009 at 19:24

    Try out http://sourceware.org/gdb/wiki/PythonGdb .
    You write some nice python scripts :)

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  4. Andy21 June 2009 at 11:29

    For some cases, it is also handy to use:

    set scheduler-locking on

    This will prevent any other threads from being run, and you can explicitly choose which thread to run (with "thread [threadnumber]").

    It lets you make your race condition a bit more deterministic.

    ReplyDelete