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52586Re: Vim SEGV after netbeans messes up syntax data structures

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  • Bram Moolenaar
    Nov 30, 2008
    • 0 Attachment
      Xavier de Gaye wrote:

      > >> >> Problem:
      > >> >> --------
      > >> >> Vim version 7.1.298 on linux.
      > >> >> Vim crashes processing received netbeans messages while redrawing the
      > >> >> windows. This happens about once every five times when running the
      > >> >> [...]
      > >> >> The following tests have been completed successfully with this patch:
      > >> >> * no Vim crash with the pyclewn test case
      > >> >> * no error reported by Valgrind with the pyclewn test case
      > >> >> * Vim does not crash when doing fast stepping with clewn
      > >> >> * netbeans does process messages when Vim is idle in normal_cmd()
      > >> >> * the full pyclewn regression test suite runs Ok.
      > >> >> [...]
      > >> >
      > >> > This will help, but I think it's still possible that Vim is updating the
      > >> > screen somewhere when a netbeans event is received. In functions called
      > >> > from normal_cmd() it's very well possible that the screen is updated
      > >> > directly instead of setting the must_redraw flag.
      > >> >
      > >> > One way to solve this is to set that callback_restricted flag in
      > >> > ui_breakcheck(). Because we don't want to handle the netbeans messages
      > >> > while checking if the user typed CTRL-C.
      > >> >
      > >> > It might still not be sufficient though. It's difficult to overview
      > >> > what happens with these asynchronous messages. And we also have to be
      > >> > careful not to block event handling (I think that happens when you would
      > >> > use the may_garbage_collect flag).
      > >> >
      > >> > Perhaps you can try out the change to ui_breakcheck() and tell us what
      > >> > happens. Perhaps there are other places where gui_mch_update() is
      > >> > called and we don't want to handle events, thus setting the flag in
      > >> > gui_mch_update() might be an alternative. But you can't do that
      > >> > always...
      > >>
      > >> Setting the callback_restricted flag in ui_breakcheck() does not work.
      > >> Most pyclewn automated tests fail because the netbeans messages are
      > >> received (and queued) in ui_breakcheck() and nb_parse_messages() never
      > >> gets a chance to process the received messages. This points out to
      > >> a problem that may occur when netbeans is run interactively: if the
      > >> last netbeans message is received in ui_breakcheck(), it is not
      > >> processed by nb_parse_messages() and appears to the user as not
      > >> received at all (until the next message arrives).
      > >> Except for that problem, this solution fixes the memory corruption as
      > >> expected in all the tests that do run.
      > >>
      > >> Another way to fix this is to prevent the netbeans callback to call
      > >> any vim function at all. This cancels the need of a global
      > >> callback_restricted flag. The callback queues the received messages
      > >> and exit the gui event loop. The messages are processed in the idle
      > >> loop where vim is waiting for character input.
      > >>
      > >> The following patch (also attached to this mail) implements this
      > >> solution for FEAT_GUI_GTK. All the tests are successful (see the list
      > >> of tests above, in the original post) including the 51 pyclewn tests.
      > >
      > > This makes sense. I'll put this in the todo list for having a closer
      > > look.
      > >
      > >> I think it is possible to implement the same solution for
      > >> FEAT_GUI_W32, but Windows support in pyclewn is not ready yet and I
      > >> don't know what application can be used to test the patch (maybe Agide ?).
      > >
      > > This should not be changed without proper testing. So let's leave it
      > > as-is until we can test it.
      >
      >
      > The problem of "Netbeans events are handled while updating the screen,
      > causing a crash" has been fixed in Vim 7.2 for gtk. The attached patch
      > to Vim 7.2.55 (subversion revision 1273) fixes this same problem for
      > Windows.
      >
      > The following tests have been completed successfully with this patch
      > and pyclewn version 0.6 on Windows:
      > * Vim processes netbeans messages when idle
      > * the full pyclewn regression test suite runs Ok
      >
      > Note that the crash could not be reproduced with Vim 7.2 and pyclewn,
      > as the current implementation of pyclewn on Windows is too slow.

      Thanks for the patch. Looks OK to me, although I can't try it out.
      I'll include it.

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