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10. Wacky stuff

Last time I promised something flashy in this post.  What could be flashier than a GUI?

Here’s some code to get you started:

from threading import Thread
import gtk

def printit ():
    print "Hello hacker"

class TestGtkThread (Thread):
    def destroy (self, *args):
        self.window.hide()

    def hello (self, *args):
        gdb.post_event (printit)

    def run (self):
        gtk.gdk.threads_init()

        self.window = gtk.Window(gtk.WINDOW_TOPLEVEL)
        self.window.connect("destroy", self.destroy)
        self.window.set_border_width(10)

        button = gtk.Button("Hello World")
        # connects the 'hello' function to the clicked signal from the button
        button.connect("clicked", self.hello)
        self.window.add(button)
        button.show()

        self.window.show_all()
        gtk.main()

class TestGtk (gdb.Command):
    def __init__ (self):
        super (TestGtk, self).__init__ ("testgtk", gdb.COMMAND_NONE,
                                         gdb.COMPLETE_NONE)
        self.init = False

    def invoke (self, arg, from_tty):
        self.dont_repeat()
        if not self.init:
            self.init = True
            v = TestGtkThread()
            v.setDaemon (True)
            v.start ()

TestGtk()

Note that we finesse the problem of main loop integration by simply starting a separate thread.  My thinking here is to just use message passing: keep gdb operations in the gdb thread, and gtk operations in the GUI thread, and send active objects back and forth as needed to do work.  The function gdb.post_event (git pull to get this) arranges to run a function during the gdb event loop; I haven’t really investigated sending events the other direction.

The above isn’t actually useful — in fact it is just a simple transcription of a python-gtk demo I found somewhere in /usr/share.  However, the point is that the addition of Python cracks gdb open: now you can combine gdb’s inferior-inspection capabilities with Python’s vast suite of libraries.  You aren’t tied to the capabilities of a given gdb GUI; you can write custom visualizers, auto-load them or load them on demand, and use them in parallel with the CLI.  If your GUI provides a CLI, you can do this without any hacks there at all; for example, this kind of thing works great from inside Emacs.

The next post is the final one in this series, I’m sorry to say.

2 Comments

  1. Johan Dahlin wrote:

    Don’t forget to call this:

    import gobject
    gobject.threads_init()

    before importing gtk. Otherwise if you starting to play around with threads, you’re going to see plenty of interesting crashes.

    Thursday, December 11, 2008 at 1:30 am | Permalink
  2. Thanks for writing this series (and the code!), it has been a good read all along. The future of GDB also looks much brighter with python scripting, I would say.

    Friday, December 12, 2008 at 12:39 pm | Permalink

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