The output of long strings through qDebug does not work properly. After 1023 characters binary characters shown up. Running in terminal mode the output is correct, but when not running in terminal mode it shows this behaviour.

See for more details https://forum.qt.io/topic/72244/limitation-of-string-length-for-qdebug-output/4

The update from creator version 4.0.3 to 4.1.0 did not change a thing.
The test example from the post above has been checked with Qt 5.4.2 and Qt 5.7.0