Thank for the experiment, quite an interesting CLion usage.

However some issues are possible here, because debugger in CLion relies on code resolving in some places and when no proper project is there, code resolve fails and some issues may appear in debugging.

Also code resolve allows you to use some smart debugger features like Inline Variable View, code completion in watches window and evaluate expression dialog, etc. Find a short overview of debugger features in CLion in our blog post: http://blog.jetbrains.com/clion/2015/05/debug-clion/

Slow watches update can happen for a big project, we are working constantly on the performance.

Attach to process is going to come in the next versions, hopefully quite soon. And CPU registers can be dump through the GDB built-in console now, some interface can come later (https://youtrack.jetbrains.com/issue/CPP-1748).