Attach to Remote Running Debugging Server with CDB

Kevin.M · wrote on 18 Jan 2023, 14:46

Hi,

So first I'm a bit new with the Qt environement.

I'm trying to remote debug a program that crash more or less randomly.
I managed to setup the remote cdb server following the Launching the Debugger documentation page.

When I launch the server with cdb.exe -server tcp:port=1234 <executable> it launches and stops at initial breakpoint until I connect to it with my local Qt Creator using "Debug -> Start Debugging -> Attach to Remote CDB Session...".
Problem is; I don't want it to wait on me to connect. It would disrupt the workflow of the people using the program so I want it to launch through CDB and me to be able to connect to it if/when it crashes.

So I found, following instructions on the CDB Command-Line Options documentation page, that launching cdb with -g will bypass the initial breakpoint.
The plan was for me to connect to the server using Qt Creator "Debug -> Start Debugging -> Attach to Running Debug Server...".

Well long story short it doesn't work.

I end up with a process that immediatly ends and this in Debugger Log (partial extract of the log)

15:38:39.290 [32ms]
sStarting debugger "CdbEngine" for ABI "x86-windows-msvc2015-pe-32bit"...
t15:38:39.290
dStart parameters: 'chla.exe  (Desktop Qt 5.6.3 MSVC2015 32bit)' mode: 6
dABI: x86-windows-msvc2015-pe-32bit
dLanguages: c++ 
dExecutable: D:\Projets\chla\build\debug\chla.exe 
dDirectory: D:\Projets\chla\build\debug
dDebugger: C:\Program Files (x86)\Windows Kits\10\Debuggers\x86\cdb.exe
dRemote: 192.168.1.97:1234
dSysroot: 
dDebug Source Location: 
t15:38:39.290
dDebugger settings: 
dUseToolTips: true  (default: true)
dBreakEvent:   (default: )
dBreakOnCrtDbgReport: true  (default: false)  ***
dSymbolPaths: D:\Temp\symbolcache  (default: )  ***
dSourcePaths:   (default: )
dGdbCustomDumperCommands:   (default: )
dAdditionalArguments:   (default: )
dAlwaysAdjustColumnWidths: true  (default: true)
dExtraDumperFile:   (default: )
dLogTimeStamps: true  (default: false)  ***
dAutoQuit: false  (default: false)
dFontSizeFollowsEditor: false  (default: false)
dUseMessageBoxForSignals: true  (default: true)
dUseAlternatingRowColours: false  (default: false)
dUseDebuggingHelper: true  (default: true)
dUseCodeModel: true  (default: true)
dRaiseOnInterrupt: true  (default: true)
dStationaryEditorWhileStepping: false  (default: false)
dSwitchModeOnExit: false  (default: false)
dBreakpointsFullPath: false  (default: false)
dCloseBuffersOnExit: false  (default: false)
dCloseMemoryBuffersOnExit: false  (default: true)  ***
dBreakOnAbort: false  (default: false)
dShowQmlObjectTree: true  (default: true)
dBreakOnWarning: false  (default: false)
dBreakOnFatal: false  (default: false)
dBreakOnThrow: false  (default: false)
dBreakOnCatch: false  (default: false)
dNoPluginBreakpoints: false  (default: false)
dSelectedPluginBreakpointsPattern: .*  (default: .*)
dQmlInspector.ShowAppOnTop: false  (default: false)
dSortStructMembers: true  (default: true)
dAutoDerefPointers: true  (default: true)
dShowQtNamespace: true  (default: true)
dShowQObjectNames: false  (default: false)
dShowStandardNamespace: true  (default: true)
dMaximalStackDepth: 20  (default: 20)
dSelectedPluginBreakpoints: false  (default: false)
dAdjustBreakpointLocations: true  (default: true)
dAllPluginBreakpoints: true  (default: true)
dSkipKnownFrames: false  (default: false)
dEnableReverseDebugging: false  (default: false)
dMaximalStringLength: 10000  (default: 10000)
dDisplayStringLimit: 100  (default: 100)
dGdbStartupCommands:   (default: )
dGdbPostAttachCommands:   (default: )
dLoadGdbDumpers2: false  (default: false)
dAttemptQuickStart: false  (default: false)
dIgnoreFirstChanceAccessViolation: true  (default: false)  ***
dLoadGdbInit: true  (default: true)
dCDB_Console: true  (default: false)  ***
dBreakpointCorrection: true  (default: true)
dIntelFlavor: false  (default: false)
dIdentifyDebugInfoPackages: false  (default: false)
dWarnOnReleaseBuilds: true  (default: true)
dMultiInferior: false  (default: false)
dUseDynamicType: true  (default: true)
dTargetAsync: false  (default: false)
dWatchdogTimeout: 20  (default: 20)
dAutoEnrichParameters: true  (default: true)
dUseAddressInStackView: false  (default: false)
dRegisterForPostMortem: false  (default: false)
dUseToolTipsInBreakpointsView: false  (default: true)  ***
dUseAddressInBreakpointsView: false  (default: false)
dUseToolTipsInLocalsView: false  (default: false)
dUseToolTipsInBreakpointsView: false  (default: false)
dShowThreadNames: false  (default: false)
t15:38:39.290
dState changed from DebuggerNotReady(0) to EngineSetupRequested(1) [master]
t15:38:39.290
dQUEUE: SETUP ENGINE
t15:38:39.313 [23ms]
dCALL: SETUP ENGINE
t15:38:39.313
 Launching C:\Program Files (x86)\Windows Kits\10\Debuggers\x86\cdb.exe -remote 192.168.1.97:1234 -lines -G -c .idle_cmd !qtcreatorcdbext.idle -x 
 using C:\Qt\Qt5.6.3\Tools\QtCreator\lib\qtcreatorcdbext32\qtcreatorcdbext.dll of 05.07.2016 03:16.
t15:38:39.313
 C:\Program Files (x86)\Windows Kits\10\Debuggers\x86\cdb.exe running as 8292
t15:38:39.313
<.load qtcreatorcdbext.dll
t15:38:39.313
dNOTE: ENGINE SETUP OK
t15:38:39.313
dState changed from EngineSetupRequested(1) to EngineSetupOk(3) [master]
t15:38:39.313
dQUEUE: SETUP INFERIOR
t15:38:39.313
dState changed from EngineSetupOk(3) to InferiorSetupRequested(4) [master]
t15:38:39.313
dQUEUE: SETUP INFERIOR
t15:38:39.343 [30ms]
dCALL: SETUP INFERIOR
t15:38:39.343
<.sympath "D:\Temp\symbolcache"
t15:38:39.343
<sxn 0x4000001f
t15:38:39.343
<sxn ibp
t15:38:39.343
<.asm source_line
t15:38:39.343
<!qtcreatorcdbext.setparameter maxStringLength=10000 maxStackDepth=20
t15:38:39.343
<pid
t15:38:39.359 [16ms]
 DebugConnect failed, Win32 error 0n87
t15:38:39.359
 The parameter is incorrect.
t15:38:39.359
 Ensure the syntax used for the transport settings is correct.
t15:38:39.359
eERROR: Process crashed
t15:38:39.359
dCDB PROCESS FINISHED, status 1, exit code -2147024809
t15:38:39.359
dNOTE: ENGINE ILL ******
t15:38:39.359
dState changed from InferiorSetupRequested(4) to EngineShutdownRequested(19) [master]
t15:38:39.359
dQUEUE: SHUTDOWN ENGINE
t15:38:39.359
dCALL: SHUTDOWN ENGINE
t15:38:39.359
dNOTE: ENGINE SHUTDOWN OK
t15:38:39.374 [15ms]
dState changed from EngineShutdownRequested(19) to EngineShutdownOk(21) [master]
t15:38:39.374
dState changed from EngineShutdownOk(21) to DebuggerFinished(22) [master]
t15:38:39.374
dQUEUE: FINISH DEBUGGER
t15:38:39.374
dNOTE: FINISH DEBUGGER
t15:38:39.374
dHANDLE RUNCONTROL FINISHED
t15:38:39.374
sDebugger finished.

I don't know if those information are useful but I'm using

Qt Creator 4.0.3

and the kit is composed of

Compiler: Microsoft Visual C++ Compiler 14.0 (x86)
Debugger: CDB (x86) 10.0.20348.1
Qt version: Qt 5.6.3 MSVC2015 32bit
CMake Tool: Cmake 32bit

What I don't understand is that I can remote debug when using "Attach to Remote CDB Session..." and the remote debugger wait on my connection but not when the server and debugger is already running.
Is there something I didn't understand or did wrong?
Is it something that only works with GDB? (someone else manage to do it with another project using GDB).

What can I do to remote debug?
Should this not be possible, is it possible to make a core dump of the program when it crashes and open it in Qt after the fact to copy the state the program was in during the crash? Is there a better way?