#1676 Memory leak connected to X11, Tk and an XCursor theme

[Petr Pajas]

I'm experiencing memory leaks in Tk-based applications
(such as demos/widget) running under X11 on SuSE
Linux 9, XFree86-4.3.0.1-46 and tk-8.4.4-57. I
discovered it only exhibits in connection with a XCursor
theme installed in .icons, but apparently not necessarily
with an arbitrary theme. So far I noticed the problem
only in connection with a theme called Siver, which can
be found at
http://www.kde-look.org/content/show.php?content=5533

The leak appers in the X process, not the Tk applications
themselves but other toolkits, like Gtk or Qt are not
affected by this. To reproduce it, install the Silver
XCursor theme and do the following:

1) run widget demo: /usr/lib/tk8.4/demos/widget

2) run top and press M to sort processes by memory
usage

3) move mouse pointer over links in the widget main
window for a while
(may take some time for the first time, but generally not
longer than
a minute - the loger )

4) watch the X process memory in top. On my setup it
grows by about
1MB/5 sec.

Petr

[Don Porter]

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report mentions the widget demos,
so I'll make that the first guess for
the Category.

[Donal K. Fellows]

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The widget demo main window is just a text widget with a few
trivial (in this aspect) bindings that switch between having
a specified cursor (i.e. non-empty -cursor option) and an
unspecified one.

Classing as a [text] bug, but I suspect the problem is
elsewhere. Assigning to someone who knows X11 better than I do.

[Joe English]

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Can't easily replicate here. Any Tk developers who use KDE?

[Joe English]

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More information: X cursor themes are apparently implemented
by the XCursor extension and a corresponding client library
libXcursor.a. Tk has no direct support for libXcursor (I
didn't even know it existed until today ...); I'd guess that
the problem is *probably* somewhere in the cursor theme,
unless maybe Tk is making assumptions about built-in cursors
that aren't valid in the presence of this extension.

Hard to say much more; there seems to be very little
information on the Web about XCursor.

[Don Porter]

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I can't confirm personally,.but I'm
hearing reports from users that
this leak is present (and hits hard!)
on the default Fedora 2 configuration.

All that's needed to produce the
leak, it seems, is iterations of:

. configure -cursor watch
. configure -cursor {}

As noted in earlier comments, the
leak is in the X server process,
not the Tk process.

[Don Porter]

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Perhaps related trouble that I can confirm:

$ make runtest
...
% testcursor watch
Segmentation Fault

[Don Porter]

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No, that just a missing initialization
in the debug routine. committing
fix just for that...

[Don Porter]

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Attached is a C program independent
of Tcl and Tk. Build it with:

gcc leak.c -o leak -L/usr/X11R6/lib -lX11

(modify as needed for your system), and
then try a run of:

leak 5000

Watch the X process for leaking memory.
Choose smaller numbers of iterations
for safety to avoid crashing X, then get
larger until you see a leak or are satisfied
this program doesn't have one.

I expect this program to leak, and demonstrate
that the bug here is in the X server, not in Tk.
Perhaps this demo program will be of help
to the X server programmers in fixing their bug.

[Don Porter]

[Joe English]

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Confirmed: while 'leak' is running, the X server process
size grows (seemingly without bounds). Once the client
exits, though, the X server quickly shrinks back to its
original size according to 'ps -l'.

This is on Debian testing, XFree86 4.3.0, Gnome 2.6 (which
uses an XCursor "cursor theme", but I'm not sure which one.)

[Joe English]

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See also: #1157298