if you attach to an runnig process thrue the output debug button, debugger cannot be startet if you have some commandline arguments.

ErrorLog:

Launching C:\Program Files (x86)\Windows Kits\10\Debuggers\x86\cdb.exe -aqtcreatorcdbext.dll -lines -G -c .idle_cmd !qtcreatorcdbext.idle -2 -y "" -p 11420 -e

Missing argument for -e

ERROR: Der Prozess ist abgestürzt

CDB PROCESS FINISHED, status 1, exit code -2147024809

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"-e" is in this case an command line argument from run settings is project config.

if you delete the argument from the config attach works....