Re: [gtk-osx-users] crash on updateTrackingRect is BAAACK

[John Ralls <jralls ceridwen us>]

> On Nov 17, 2020, at 7:52 AM, Allin Cottrell <cottrell wfu edu> wrote:
>
> On Mon, 16 Nov 2020, John Ralls wrote:
>
> > > On Nov 16, 2020, at 1:46 PM, Allin Cottrell via gtk-osx-users-list <gtk-osx-users-list gnome org> wrote:
> > >
> > > Back in 2106 there was a thread concerning a crash on macOS when (a) a GTK window is maximized, then (b) 
> > > the user tries to close the maximized window via the quartz control button ("x"). See
> > > https://mail.gnome.org/archives/gtk-osx-users-list/2016-February/msg00005.html
> > > and following.
> > >
> > > I thought we were done with that; there seemed to be fix in hand and no more was heard of the problem. 
> > > But now I'm seeing the same thing again -- this is with GTK 2.24.32 on macOS 10.15.7. The crash report 
> > > from the OS looks just like before, with the coup de grace in this sequence:
> > >
> > > Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
> > > 0 libgdk-quartz-2.0.0.dylib 0x000000010bb690a5 -[GdkQuartzView updateTrackingRect] + 37
> > > 1 libgdk-quartz-2.0.0.dylib 0x000000010bb69249 -[GdkQuartzView setFrame:] + 105
> > > 2 com.apple.AppKit          0x00007fff2d5d889b -[NSThemeFrame setStyleMask:] + 1008
> > >
> > > Any ideas on what might have changed to allow this bug to re-emerge?
> > >
> > > Just for reference, here's the code for the function at issue, in GdkQuartzView.c. In 2016 the problem 
> > > was handled by checking for "!impl" as well as "!impl->toplevel" before doing anything substantive. Now 
> > > apparently that is not sufficient. [...]
> >
> > It's probably a use-after-free where private->impl has been freed but not NULLed. Address sanitizer is the 
> > fastest way to track down problems like that. I haven't been working much with Gtk2 in the last couple of 
> > years but The GIMP still does. Unfortunately I don't think any of them subscribe here so I suggest you 
> > open an issue at https://gitlab.gnome.org/GNOME/gtk.
>
> John, thanks for forwarding my message to the gnome guys, but Emmanuele's response was kinda what I was 
> expecting ("You're on your own with GTK 2").
>
> However, when we fixed the previous incarnation of this bug, IIRC you also submitted a patch for GTK 3 -- 
> so perhaps this mutation of the bug also affects GTK 3? That would be interesting to know.
>
> I have one thought about taking this further. Last time around we put in a "nullify a pointer" callback for 
> windowWillClose (in GdkQuartzWindow.c). I wonder if we now need a similar callback for a different event 
> specification. I'll see what I can figure out.
>
> One other point: Do you know if there's any way to disable the maximize control for an application's quartz 
> window? Current macOS maps this to "Full Screen" (task bar hidden) and there's really no reason for anyone 
> to run my application in that mode, so blocking or re-mapping the maximize action would be a possible 
> workaround. (The
> crash seems to be specific to closing a maximized window.)

Allin,

Gtk-osx is a Gnome project hosted on Gnome's Gitlab and this is a Gnome mailing list hosted on 
lists.gnome.org. No forwarding required!

Emmanuel didn't say "you're on your own", he said that time is running out and to get patches in ASAP.

There's a message in there, though: It's past time to migrate your app to Gtk3. Gtk2 might work OK in macOS 
11 (I haven't done anything more than cursory does-it-build checks) but Apple has a history of changing their 
APIs and at some point Gtk2 will stop working on some future version of macOS.

This SO suggests one way to prevent full-screen: 
https://stackoverflow.com/questions/33457029/osx-disable-fullscreen-mode-from-the-zoom-button
 
I just tested full-screening and red button closing GnuCash built yesterday with Gtk+-3.24.23 on macOS 11 and 
run with MallocScribble=1 to make sure that a use-after-free would crash. It closed cleanly, no crash. You 
might diff GtkNSWindow.c between Gtk2 and Gtk3 to see if there's something helpful there.

Regards,
John Ralls