> A quirk in the messaging system rears its head when you try to write a Windows-hosted debugger (also called a "GUI debugger"). A GUI debugger is a debugger for Windows programs that itself uses the Windows display mechanisms. What's the problem with that? Well, imagine the following scenario: A GUI debugger places a breakpoint inside of a Window procedure. Eventually, the debuggee program hits the breakpoint, and stops--and cannot call GetMessage() to yield control to other tasks! That means no other tasks--including the GUI debugger--can get their messages. The debugger can't even respond the mouse clicks that tell the debuggee to run again.

That’s unfortunate