User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0 Build ID: 20170630221752 Steps to reproduce: When running the JWM window manager, double-clicking the empty toolbar area to the right of the [ + ] (new tab) button, Firefox maximizes. When double-clicked again, Firefox crashes. The red arrow in the attached image shows where I double-clicked to cause this crash. This occurs on Debian Linux 64-bit, Void Linux 64-bit and FreeBSD 11.0 64-bit. Actual results: Firefox crashes after double-clicking the empty toolbar area to the right of the 'new tab' button. Here is the related output on the terminal: Gdk:ERROR:gdkwindow-x11.c:5165:create_moveresize_window: assertion failed: (mv_resize->moveresize_emulation_window == NULL) Redirecting call to abort() to mozalloc_abort [Child 1599] ###!!! ABORT: Aborting on channel error.: file /builddir/firefox-52.2.1esr/ipc/glue/MessageChannel.cpp, line 2152 [Child 1599] ###!!! ABORT: Aborting on channel error.: file /builddir/firefox-52.2.1esr/ipc/glue/MessageChannel.cpp, line 2152 Segmentation fault Expected results: Firefox should not have crashed. On other window managers, the mouse pointer quickly turns to the 'drag' cursor then back to the default cursor when this area is double-clicked.

Bug report at the JWM github site: https://github.com/joewing/jwm/issues/385

(In reply to YF (Yang) from comment #2) > https://developer.mozilla.org/en-US/docs/ > How_to_get_a_stacktrace_for_a_bug_report The crash ID is: bp-e440280d-fdaf-4f77-a219-cb26f0170709

This issue also occurs on TWM. Additional operating system where this crash happens is OpenBSD 6.1 64-bit.

Based on further testing, Firefox 45.0.2 was the last version that *didn't* crash when the empty space next to the 'New Tab' button is double-clicked. Instead of crashing, 45.0.2 opens a new tab when the area in question is double-clicked. 45.0.2 also appears to be the last major Firefox version that is Gtk 2. Looks like the issue might be based on the migration to Gtk 3.

In the past week I'm only seeing 11 crashes reported. Wontfixing this for 57 and 58, keeping open.