gdb behaviour change under software watchpoints?

A bug in my software is revealed by a debug build which eventually calls
abort(). gdb sees and reports this and I can do a backtrace and find a
memory location I need to investigate.
then I make a run with a watchpoint on said memory location which has to be
software since it's a non-host binary running under qemu.
not only does the watchpoint not get triggered despite ensuring binary is
being loaded to the same address, but gdb only reports that the process has
exitted with an error code - no memory to examine, no backtrace.

the former is mysterious but the latter is annoying - is this behaviour
necessitated by setting watchpoints?
I have remote access to a machine of the target variety but I would ask
first whether I can expect the behaviour to return to normal when using a
hardware watchpoint. No point is going down a dead end...
Thanks.