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
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:] + 

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 Cottrell
Department of Economics
Wake Forest University
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