Thread awareness in remote serial protocol Z packet

[Earl Chew]

I'm implementing a remote serial protocol agent. The target
supports global and thread specific breakpoints.

Reading the documentation for Zt,addr,length and browsing
breakpoint_thread_match() and insert_breakpoints() in
gdb/breakpoint.c (gdb 5.0) suggests that gdb can only cause the
remote to insert global breakpoints, then check after the
breakpoint is reached as to which thread caused the break.

Is this correct?

Under some circumstances it would be advantageous to have
the remote filter the breakpoints to avoid many false
stop/starts.

Perhaps extended the Z protocol to allow Zt,addr,length,id
(plus the corresponding change in breakpoint.c) would be sufficient
to allow this. Old targets presumably would ignore the ,id
argument and proceed as before.

Earl