Ehhh. Problem is most likely caused by "No source file" and it affects normal projects too. I don't know how to solve it, as path to source files doesn't contain spaces or non-ASCII characters.
Only place, where breakpoints work - startup code. It's very strange, because startup file is placed in exactly the same directory, as main project file. But even in this case GDB doesn't work properly - program execution is stopped, but breakpoint isn't triggered in code editor. If I attempt to resume execution - program just crashes.