Tk Source Code

The [focus] command will dump core if the target window
is a widget
with certain unusual characteristics. If the target
window is the top
of a window hierarchy but is NOT a toplevel with a
wrapper window,
it will core dump. To demonstrate the problem, get the
"rootwin"
widget extension (which makes the X display's root
window into
a Tk widget):

 
http://www.eecs.umich.edu/~mckay/computer/rootwin0.4.tar.gz

Then do the following:

  load /path/to/libRootwin0.4.so
  rootwin .r
  focus -force .r

The problem is in tkFocus.c; I fixed it, and the diff
looks like:


diff tkFocus.c.orig tkFocus.c
565c565
<     TkWindow *topLevelPtr;
---
>     TkWindow *topLevelPtr, *focusToplevelPtr;
667c667,671
<       serial =
TkpChangeFocus(TkpGetWrapperWindow(topLevelPtr), force);
---
>       focusToplevelPtr =
TkpGetWrapperWindow(topLevelPtr);
>       if (focusToplevelPtr == NULL) {
>           focusToplevelPtr = topLevelPtr;
>       }
>       serial = TkpChangeFocus(focusToplevelPtr, force);

NOTE: there's a bad line break in the diff, but you can
see that
the fix is simple. Address questions to:

  mckay at eecs dot umich dot edu

Backported to 8.6 in [49d74ea438].

Fixed in [78b981bf|trunk] and core-9-0-branch

Many thanks! Closing

Still relevant: TkSetFocusWin() passes the result of TkpGetWrapperWindow() to TkpChangeFocus() unchecked, and on X11 it is NULL for a top of hierarchy window without wm information. Applied the suggested fix: focus now uses the window itself when it has no wrapper, instead of crashing. Fixed in [65b5b1ae41] (branch focus-no-wrapper).

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Yes, I believe this bug is still relevant post TIP#153. In
fact this bug has to be fixed in order for TIP#153 to be
useful. This is a place where the Tk code assumes that the
top-level window in a hierarchy is an actual [toplevel]
widget (or, more correctly, it assumes that the
top-of-hierarchy widget has a wrapper window). If it is not
a toplevel, the code dereferences a NULL pointer.

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Is this still relevant post TIP#153?

File Added - 50089: tkFocus.704212

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attached is a clean patch against the HEAD, but I have focus 
issues when running the tests on linux that I would like to 
understand better first.