Eclipse C/C++: Cannot open output file *.exe: Permission denied

Problem: you want to build/compile your project and you get the error:

cannot open output file FOO.exe: Permission denied

Solution: It's most likely that your EXE is running and can't be overwritten by the compile process. You have to stop all running processes of your EXE. The ones started within Eclipse can be stopped in the debug perspective: Choose all running processes and press the stop button...

If the problem is still not solved, you may have started the EXE outside Eclipse. Go to the task manager (in Windows) > Processes and stop your EXEs.