Set text on a destroyed actor could crash g-s

[3v1n0]

This line (very likely) https://github.com/codito/gnome-pomodoro/blob/75e2f7acb52e26a5abfc8a0a3305dc3c03c7cf54/plugins/gnome/extension/dialogs.js#L647

Causes gnome-shell to crash, you should connect on actor destroy signal and nullify the pointer or just stop the timer.

This is bug has been reported in ubuntu: https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1714989

oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: == Stack trace for context 0x55cfe600e000 ==
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #0 0x55cfe6223678 i   /usr/share/gnome-shell/extensions/pomodoro@arun.codito.in/dialogs.js:140 (0x7fd8162bb3c8 @ 93)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #1 0x7ffc57a5a520 I   resource:///org/gnome/gjs/modules/_legacy.js:82 (0x7fd8541c2c48 @ 71)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #2 0x55cfe62235d0 i   /usr/share/gnome-shell/extensions/pomodoro@arun.codito.in/dialogs.js:121 (0x7fd8162bb2b8 @ 104)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #3 0x7ffc57a5b130 I   resource:///org/gnome/gjs/modules/_legacy.js:82 (0x7fd8541c2c48 @ 71)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #4 0x7ffc57a5b1c0 I   self-hosted:917 (0x7fd8541ee4d8 @ 394)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #5 0x7ffc57a5b250 I   resource:///org/gnome/gjs/modules/signals.js:126 (0x7fd8541e2c48 @ 386)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #6 0x55cfe6223518 i   resource:///org/gnome/shell/ui/messageTray.js:1031 (0x7fd84151a918 @ 200)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #7 0x7ffc57a5be60 I   resource:///org/gnome/gjs/modules/_legacy.js:82 (0x7fd8541c2c48 @ 71)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #8 0x55cfe6223480 i   resource:///org/gnome/shell/ui/messageTray.js:1054 (0x7fd84151aab0 @ 90)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #9 0x7ffc57a5ca70 I   resource:///org/gnome/gjs/modules/_legacy.js:82 (0x7fd8541c2c48 @ 71)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #10 0x55cfe62233d0 i   resource:///org/gnome/shell/ui/messageTray.js:1016 (0x7fd84151a890 @ 208)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #11 0x7ffc57a5d680 I   resource:///org/gnome/gjs/modules/_legacy.js:82 (0x7fd8541c2c48 @ 71)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #12 0x55cfe6223320 i   resource:///org/gnome/shell/ui/notificationDaemon.js:199 (0x7fd840b55560 @ 335)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #13 0x7ffc57a5e2a0 I   resource:///org/gnome/gjs/modules/_legacy.js:82 (0x7fd8541c2c48 @ 71)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #14 0x55cfe6223270 i   resource:///org/gnome/shell/ui/notificationDaemon.js:300 (0x7fd840b55780 @ 207)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #15 0x7ffc57a5eef0 I   self-hosted:917 (0x7fd8541ee4d8 @ 394)
oct. 22 15:49:15 matteo-XPS org.gnome.Shell.desktop[1120]: #16 0x7ffc57a5efc0 b   resource:///org/gnome/gjs/modules/overrides/Gio.js:90 (0x7fd841603670 @ 118)

[kamilprusko]

Thanks for detailed report.

Looks like this issue is reported on gnome-shell bugzilla https://bugzilla.gnome.org/show_bug.cgi?id=788931

Storing a St.Label instance should bump its reference counter. In the offending line, it tries to read "clutter-text" property and call set_text() - I assume segfault happens because St.Label holds a broken reference in the property.