I’m using Eclipse CDT on Linux. My F5/F6/F7/F8 keys are set to their default configuration. When I start debugging, however, sometimes they won’t and sometimes they don’t – meaning, clicking them does nothing. If they work they will remain working as long as the debugged program run, and the same if they don’t.
I can verify from the menu that sometimes the shortcuts are indeed active, and sometimes not – the two screenshots below were from two different debugging sessions but with no configuration change between them.
The problem was most likely an issue with the “debug” action group in the Debug perspective setup. Even though it looked active all the time, something must have gone wrong with it. I’ve solved the issue by resetting the debug perspective (you can reset from the Window menu, or just right-click the perspective in the top-right).