macOS: Repeated crash in NSScrollerImp drawKnobSlotInRect on background thread #2425
Description
Environment
- OS: macOS 15.7.4 (24G517), ARM64
- Mac Model: Mac16,10
- HeidiSQL Version: 12.15.1.1 (macOS .app bundle)
- MySQL Server: 8.4.8
Description
HeidiSQL crashes repeatedly on macOS when a scrollbar is being rendered on a background thread. I experienced 5 crashes within 4 minutes today (2026-03-09, between 09:58 and 10:02).
The root cause appears to be a UI operation (scrollbar drawing) happening on a non-main thread, which violates macOS/AppKit's requirement that all UI work must occur on the main thread.
Crash Flow
NSScrollerImp drawKnobSlotInRect:highlight:alpha:is called on a background thread (Thread 9)CUIRenderer::Draw()failsFPC_BREAK_ERRORtriggers a Free Pascal runtime error- The exception handler (
MAIN$_$TMAINFORM_$__$$_APPLICATIONEXCEPTION) tries to show a modal error dialog viaShowModal— still on the background thread NSWindow initWithContentRect:styleMask:backing:defer:throws anNSExceptionbecause window creation is not allowed off the main thread- This leads to
objc_exception_throw→abort()→EXC_BREAKPOINT (SIGTRAP)
Crashing Thread Stack Trace (Thread 9)
__abort
abort
abort_message
demangling_terminate_handler()
_objc_terminate()
std::__terminate(void (*)())
__cxxabiv1::failed_throw(__cxxabiv1::__cxa_exception*)
__cxa_throw
objc_exception_throw
-[NSException raise]
-[NSWindow _initContent:styleMask:backing:defer:contentView:]
-[NSWindow initWithContentRect:styleMask:backing:defer:]
COCOAWSFORMS$_$TCOCOAWSCUSTOMFORM_$__$$_CREATEHANDLE$TWINCONTROL$TCREATEPARAMS$$QWORD
CONTROLS$_$TWINCONTROL_$__$$_CREATEWND
FORMS$_$TSCROLLINGWINCONTROL_$__$$_CREATEWND
FORMS$_$TCUSTOMFORM_$__$$_CREATEWND
FORMS$_$TFORM_$__$$_CREATEWND
CONTROLS$_$TWINCONTROL_$__$$_CREATEHANDLE
CONTROLS$_$TWINCONTROL_$__$$_HANDLENEEDED
CONTROLS$_$TWINCONTROL_$_DOALLAUTOSIZE_$$_CHECKHANDLEALLOCATED$TWINCONTROL$$BOOLEAN
CONTROLS$_$TWINCONTROL_$__$$_DOALLAUTOSIZE
CONTROLS$_$TCONTROL_$__$$_ENABLEAUTOSIZING
CONTROLS$_$TCONTROL_$__$$_SETVISIBLE$BOOLEAN
FORMS$_$TCUSTOMFORM_$__$$_SETVISIBLE$BOOLEAN
FORMS$_$TCUSTOMFORM_$__$$_SHOW
FORMS$_$TCUSTOMFORM_$__$$_SHOWMODAL$$LONGINT
MAIN$_$TMAINFORM_$__$$_APPLICATIONEXCEPTION$TOBJECT$EXCEPTION
FORMS$_$TAPPLICATION_$__$$_HANDLEEXCEPTION$TOBJECT
FORMS_$$_EXCEPTIONOCCURRED$TOBJECT$POINTER$LONGINT$PPOINTER
SYSTEM_$$_DOUNHANDLEDEXCEPTION
FPC_RAISEEXCEPTION
SYSUTILS_$$_RUNERRORTOEXCEPT$LONGINT$POINTER$POINTER
FPC_BREAK_ERROR
CUIRenderer::Draw(CGRect, CGContext*, __CFDictionary const*, __CFDictionary const**)
CUIDraw
-[NSCompositeAppearance _callCoreUIWithBlock:options:requireBezelTintColor:]
-[NSAppearance _drawInRect:context:options:]
-[NSScrollerImp drawKnobSlotInRect:highlight:alpha:]
-[TCocoaScrollBar drawKnobSlotInRect:highlight:]
-[NSScroller drawRect:]
_NSViewDrawRect
-[NSView _recursive:displayRectIgnoringOpacity:inContext:stopAtLayerBackedViews:]
-[NSView(NSLayerKitGlue) _drawViewBackingLayer:inContext:drawingHandler:]
-[NSViewBackingLayer drawInContext:]
-[NSViewBackingLayer display]
CA::Layer::display_if_needed(CA::Transaction*)
CA::Context::commit_transaction(CA::Transaction*, double, double*)
CA::Transaction::commit()
CA::Transaction::release_thread(void*)
_pthread_tsd_cleanup
_pthread_exit
pthread_exit
CTHREADS_$$_CENDTHREAD$LONGWORD
SYSTEM_$$_ENDTHREAD$LONGWORD
CLASSES_$$_THREADFUNC$POINTER$$INT64
CTHREADS_$$_THREADMAIN$POINTER$$POINTER
_pthread_start
thread_start
Exception Details
Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000001, 0x000000018d024a94
Termination: Trace/BPT trap: 5
ASI: libsystem_c.dylib - abort() called
Suggested Fix
- Ensure all scrollbar rendering (
TCocoaScrollBar drawKnobSlotInRect:) is dispatched to the main thread - The exception handler (
ApplicationException→ShowModal) should check if it's on the main thread before attempting to create a window, or useTThread.Synchronize/dispatch_async(dispatch_get_main_queue(), ...)to show the dialog on the main thread
Crash Reports
All 5 crash reports (.ips files) are available if needed.