If you run "gdb -i=mi2" and set a "display", then when "next"ing the
displays will be shown twice:
~"1: x = 23\n"
~"7\t printf(\"%d\\n\", x);\n"
~"1: x = 23\n"
*stopped,reason="end-stepping-range",frame={addr="0x0000000000400565",func="main",args=[],file="q.c",fullname="/tmp/q.c",line="7"},thread-id="1",stopped-threads="all",core="1"
The immediate cause of this is this code in mi_on_normal_stop_1:
print_stop_event (mi_uiout);
console_interp = interp_lookup (current_ui, INTERP_CONSOLE);
if (should_print_stop_to_console (console_interp, tp))
print_stop_event (mi->cli_uiout);
... which obviously prints the stop twice.
However, I think the first call to print_stop_event is intended just
to emit the MI *stopped notification, which explains why the source
line does not show up two times.
This patch fixes the bug by changing print_stop_event to only call
do_displays for non-MI-like ui-outs.