gcode: guard NULL chained on_settings_changed in onSettingsChanged - #999
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gcode: guard NULL chained on_settings_changed in onSettingsChanged#999ScottW514 wants to merge 1 commit into
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terjeio
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Aug 3, 2026
gc_init subscribes to grbl.on_settings_changed by capturing the previous handler to chain it. When no plugin or driver has subscribed before the first gc_init, the captured pointer is NULL and the chained call in onSettingsChanged dereferences it - every runtime $-setting write then crashes on drivers with no other subscriber (observed live with the Simulator). The core dispatcher already NULL-checks its own pointer; this adds the same guard to the chained tail.
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gc_init()subscribes togrbl.on_settings_changedby capturing the previous handler so it can chain it:When no plugin or driver has subscribed before the first
gc_init()runs, the captured pointer is NULL, and the chained call at the top ofonSettingsChanged()dereferences it. On builds with no other subscriber, every runtime$-setting write then crashes (observed live with the Simulator: any$xx=yysegfaulted).The core dispatcher in grbllib.c already NULL-checks its own
grbl.on_settings_changedbefore calling; this adds the same guard to the chained tail in gcode.c. No behavior change when a subscriber exists.Reproduce (before this fix): build the Simulator, connect, send any
$-setting write, e.g.$110=6000- the process crashes inonSettingsChanged().