The debug controls in Qt Creator have the following three consecutive buttons:
run/pause, stop/exit, step-over.

It is relatively easy to accidentally hit stop/exit when trying to press either run or step over. So, the placement of the buttons is not optimal from an user experience point of view.

As a suggestion:
moving the stop/exit button for example to the end of the row, to the right of the restart button, would greatly improve the user experience as accidentally pressing stop button would not happen when pressing the some of the mostly used buttons in debugger.