Don't show "display"s twice in MI

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.

Tested on x86-64 Fedora 29.

gdb/ChangeLog
2019-03-19  Tom Tromey  <tromey@adacore.com>

	* mi/mi-interp.c (mi_on_normal_stop_1): Only show displays once.
	* infrun.h (print_stop_event): Add "displays" parameter.
	* infrun.c (print_stop_event): Add "displays" parameter.

gdb/testsuite/ChangeLog
2019-03-19  Tom Tromey  <tromey@adacore.com>

	* gdb.mi/mi2-cli-display.c: New file.
	* gdb.mi/mi2-cli-display.exp: New file.

7 files changed, 142 insertions, 6 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index c170fe4..be65681 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2019-03-19  Tom Tromey  <tromey@adacore.com>
+
+	* mi/mi-interp.c (mi_on_normal_stop_1): Only show displays once.
+	* infrun.h (print_stop_event): Add "displays" parameter.
+	* infrun.c (print_stop_event): Add "displays" parameter.
+
 2019-03-19  Pedro Alves  <palves@redhat.com>
 
 	* tui/tui-out.c (tui_ui_out::do_field_string): Simplify.
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 3d7f36b..550fbe7 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -7856,7 +7856,7 @@ print_stop_location (struct target_waitstatus *ws)
 /* See infrun.h.  */
 
 void
-print_stop_event (struct ui_out *uiout)
+print_stop_event (struct ui_out *uiout, bool displays)
 {
   struct target_waitstatus last;
   ptid_t last_ptid;
@@ -7870,7 +7870,8 @@ print_stop_event (struct ui_out *uiout)
     print_stop_location (&last);
 
     /* Display the auto-display expressions.  */
-    do_displays ();
+    if (displays)
+      do_displays ();
   }
 
   tp = inferior_thread ();
diff --git a/gdb/infrun.h b/gdb/infrun.h
index 8f61b75..e53fd81 100644
--- a/gdb/infrun.h
+++ b/gdb/infrun.h
@@ -167,9 +167,10 @@ extern void print_return_value (struct ui_out *uiout,
 
 /* Print current location without a level number, if we have changed
    functions or hit a breakpoint.  Print source line if we have one.
-   If the execution command captured a return value, print it.  */
+   If the execution command captured a return value, print it.  If
+   DISPLAYS is false, do not call 'do_displays'.  */
 
-extern void print_stop_event (struct ui_out *uiout);
+extern void print_stop_event (struct ui_out *uiout, bool displays = true);
 
 /* Pretty print the results of target_wait, for debugging purposes.  */
 
diff --git a/gdb/mi/mi-interp.c b/gdb/mi/mi-interp.c
index f17e09f..3c5a0d8 100644
--- a/gdb/mi/mi-interp.c
+++ b/gdb/mi/mi-interp.c
@@ -625,10 +625,15 @@ mi_on_normal_stop_1 (struct bpstats *bs, int print_frame)
 	  reason = tp->thread_fsm->async_reply_reason ();
 	  mi_uiout->field_string ("reason", async_reason_lookup (reason));
 	}
-      print_stop_event (mi_uiout);
 
       console_interp = interp_lookup (current_ui, INTERP_CONSOLE);
-      if (should_print_stop_to_console (console_interp, tp))
+      /* We only want to print the displays once, and we want it to
+	 look just how it would on the console, so we use this to
+	 decide whether the MI stop should include them.  */
+      bool console_print = should_print_stop_to_console (console_interp, tp);
+      print_stop_event (mi_uiout, !console_print);
+
+      if (console_print)
 	print_stop_event (mi->cli_uiout);
 
       mi_uiout->field_int ("thread-id", tp->global_num);
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index e0bed87..636800f 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-03-19  Tom Tromey  <tromey@adacore.com>
+
+	* gdb.mi/mi2-cli-display.c: New file.
+	* gdb.mi/mi2-cli-display.exp: New file.
+
 2019-03-18  Joel Brobecker  <brobecker@adacore.com>
 	    Tom Tromey  <tromey@adacore.com>
 
diff --git a/gdb/testsuite/gdb.mi/mi2-cli-display.c b/gdb/testsuite/gdb.mi/mi2-cli-display.c
new file mode 100644
index 0000000..552612d
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi2-cli-display.c
@@ -0,0 +1,32 @@
+/* Copyright 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int
+do_tests (int x)
+{
+  ++x;
+  ++x;
+  ++x;
+  ++x;
+  return x;
+}
+
+int
+main (void)
+{
+  return do_tests (23);
+}
diff --git a/gdb/testsuite/gdb.mi/mi2-cli-display.exp b/gdb/testsuite/gdb.mi/mi2-cli-display.exp
new file mode 100644
index 0000000..e12fe72
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/mi2-cli-display.exp
@@ -0,0 +1,86 @@
+# Copyright 2019 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Ensure that CLI "display"s aren't double-emitted in MI mode.
+
+load_lib mi-support.exp
+set MIFLAGS "-i=mi2"
+
+if {[mi_gdb_start]} {
+    continue
+}
+
+standard_testfile
+
+if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+    untested "failed to compile"
+    return -1
+}
+
+mi_delete_breakpoints
+mi_gdb_reinitialize_dir $srcdir/$subdir
+mi_gdb_load ${binfile}
+
+mi_runto do_tests
+
+# A helper procedure that checks for the display and the line number,
+# and the following *stopped.  X is the expected value of "x" and is
+# also used in test names.
+proc check_cli_display {x show_source} {
+    global mi_gdb_prompt
+
+    # Now check for the display and the source line.  We don't check
+    # the source line too closely, since it's not really important
+    # here, but we do check that the stop happened.
+    set stop "\\*stopped,reason=.*\r\n$mi_gdb_prompt$"
+    if {$show_source} {
+	set src "~\"\[0-9\]+\[^\"\]*\\\\n\"\r\n"
+    } else {
+	set src ""
+    }
+    set display "~\"1: x = $x\\\\n\"\r\n"
+    gdb_expect {
+	-re "^${display}${src}${display}${stop}" {
+	    # This case is the bug: the display is shown twice.
+	    fail "check display and source line x=$x"
+	}
+	-re "^${src}${display}${stop}" {
+	    verbose -log "got <<<$expect_out(buffer)>>>"
+	    pass "check display and source line x=$x"
+	}
+	-re ".*\r\n$mi_gdb_prompt$" {
+	    verbose -log "got <<<$expect_out(buffer)>>>"
+	    fail "check display and source line x=$x (unexpected output)"
+	}
+	timeout {
+	    fail "check display and source line x=$x (timeout)"
+	}
+    }
+}
+
+mi_gdb_test "display x" \
+    "&\"display x\\\\n\"\r\n~\"1: x = 23\\\\n\"\r\n\\^done" \
+    "display x"
+
+if {![mi_send_resuming_command "interpreter-exec console next" next]} {
+    pass "next"
+}
+check_cli_display 24 1
+
+# Also check that displays are shown for -exec-next.
+if {![mi_send_resuming_command exec-next exec-next]} {
+    pass "-exec-next"
+}
+check_cli_display 25 0