Watchpoints with condition

[Russell Shaw]

Vladimir Prus wrote:
> GDB presently allow a watchpoint to have a condition, and I wonder
> what are the use-cases for that.
> 
> If anybody has used watchpoint in condition in practice when debugging
> real problem (as opposed to just playing with gdb, or making up
> possible uses), can he share why it was needed?

I frequently need to enable or set a breakpoint only if another
previous point in the program has been passed. How do i do that?