On Apr 24, 2018, at 5:38 PM, Kyle Owen via cctalk <cctalk at classiccmp.org> wrote: I haven't seen one. But it would certainly make sense to tie in a GDB remote protocol server, hooked to the breakpoint facility of the SIMH emulation for machines that have one. One drawback is that there aren't all that many SIMH architectures that have GDB support. VAX does, and Alpha; that's about it. I don't know how hard it is to do a basic platform in GDB, probably not all that difficult. At least for machines like PDP-11. One's complement might be harder (PDP-1), never mind things like the IBM 1620... :-) paul

True. But if the SIMH code has breakpoint support, GDB can use that as a "hardware breakpoint". Not all that interesting, perhaps, unless you're putting breakpoints in ROM. More interesting is watchpoint support, which some SIMH targets have, and GDB supports. I haven't tried to do a minimal BFD/opcodes implementation for a platform that doesn't yet have one. PDP-10 perhaps (unless Lars did one years ago?). One wonders if non-power-of-two wordlengths add complication, as they do in recent GCC. I don't know if the SIMH execution and control frameworks make it convenient to hook up the GDB remote stub protocol. A stop to the SIMH console would want to be turned into a GDB remote interaction instead, and break signals from GDB would have to be recognized while SIMH is running the emulated machine. paul