[PATCH] [gdb/tui] Handle tui disable in new ui

[Tom de Vries <tdevries@suse.de>]

I tried out the following scenario.

First, I start a terminal to get a tty [1].
...
$ gnome-terminal -- bash -c "tty; sleep 999999999" &
...

Then I start gdb, and start a new UI in the tty:
...
$ gdb
(gdb) new-ui console /dev/pts/3
New UI allocated
(gdb)
...

Now I have two terminals, each with a gdb prompt.

I try in the new UI to enable TUI:
...
(gdb) tui enable
❌️ Cannot enable the TUI when the interpreter is 'console'
(gdb)
...
but that is not allowed.

So instead, I enable TUI in the main UI.  So far so good.

Now I disable TUI in the new UI.  That leaves the new UI in this state:
...
(gdb) tui disable
<blinking cursor>
...
So, no gdb prompt.

The main UI does leave TUI, AFAICT.

If I do "print 1<enter>" in the new UI, I get the result in the main UI, which
is not supposed to happen.

Fix this by instead throwing an error if we try to disable TUI in the new UI:
...
(gdb) tui disable
❌️ Cannot enable  or disablethe TUI when the interpreter is 'console'
(gdb)
...

We could try to fix this instead by allowing tui enable/disable from the new
UI, using:
...
  scoped_restore restore_interpreter
    = make_scoped_restore (&current_ui, main_ui);
...
but with just that change, when doing "tui enable" in the new UI we do get a
TUI layout in the main UI, but no gdb prompt.  The prompt does appear after a
new keystroke in the main UI though.

A few more TUI commands (for instance "layout asm") have the same problem:
- they work when entered in the new UI,
- they have an effect in the main UI, but
- they don't show a prompt in the main UI.

I left that problem as is, and exercised some TUI commands in a new UI in the
test-case.

Tested on x86_64-linux.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34035
---
 gdb/testsuite/gdb.tui/new-ui.exp | 93 ++++++++++++++++++++++++++++++++
 gdb/tui/tui.c                    | 18 +++++--
 2 files changed, 107 insertions(+), 4 deletions(-)
 create mode 100644 gdb/testsuite/gdb.tui/new-ui.exp

diff --git a/gdb/testsuite/gdb.tui/new-ui.exp b/gdb/testsuite/gdb.tui/new-ui.exp
new file mode 100644
index 00000000000..8fe3567077a
--- /dev/null
+++ b/gdb/testsuite/gdb.tui/new-ui.exp
@@ -0,0 +1,93 @@
+# Copyright 2026 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/>.
+
+# Test TUI in combination with a new UI.
+
+tuiterm_env
+
+# Creating a pty is done on build, and we use it with gdb on host, so we need
+# build == host, in other words, local host.
+require {!is_remote host}
+
+# Create a pty.
+spawn -pty
+set new_ui_spawn_id $spawn_id
+set new_ui_tty_name $spawn_out(slave,name)
+
+set re_cannot_enable_disable_tui \
+    "Cannot enable or disable the TUI when the interpreter is 'console'"
+
+with_test_prefix main-ui {
+    Term::clean_restart 24 80
+
+    # Check that we cannot setup a new tui UI.  Also checked in
+    # gdb.base/new-ui.exp.
+    gdb_test "new-ui tui $new_ui_tty_name" \
+	"interpreter 'tui' cannot be used with a new UI" \
+	{new-ui tui $new_ui_tty_name}
+
+    # Set up a new console UI.
+    gdb_test "new-ui console $new_ui_tty_name" \
+	"New UI allocated" \
+	{new-ui cli $new_ui_tty_name}
+}
+
+with_test_prefix new-ui {
+    with_spawn_id $new_ui_spawn_id {
+	# Check that we cannot enable TUI in the new UI.
+	gdb_test "tui enable" $re_cannot_enable_disable_tui
+    }
+}
+
+with_test_prefix main-ui {
+    if {![Term::enter_tui]} {
+	unsupported "TUI not supported"
+	return
+    }
+}
+
+with_test_prefix new-ui {
+    with_spawn_id $new_ui_spawn_id {
+	# Check that we cannot disable TUI in the new UI.
+	# Regression test for PR34035.  Without the fix, this test will timeout,
+	# because no prompt will appear.
+	gdb_test "tui disable" $re_cannot_enable_disable_tui
+
+	gdb_test "print 1" \
+	    [quotemeta {$@DECIMAL = 1}] \
+	    "Check that UI is responsive"
+    }
+
+    # Try out some TUI commands.  We don't check for the effect in the main
+    # UI, we just check that the main UI is still responsive at the end.
+    with_spawn_id $new_ui_spawn_id {
+	gdb_test "info win" [quotemeta "@...(has focus)@..."]
+
+	gdb_test "focus cmd" \
+	    [string_to_regexp "Focus set to cmd window."]
+
+	# This command leaves a blinking cursor at the end of the status line.
+	gdb_test_no_output "layout asm"
+
+	gdb_test "winheight asm +1"
+	gdb_test_no_output "tui refresh"
+    }
+}
+
+with_test_prefix main-ui {
+    gdb_assert {[Term::command "print 1"]} \
+	"Check that UI is responsive"
+    Term::dump_screen
+}
diff --git a/gdb/tui/tui.c b/gdb/tui/tui.c
index 9cf21f390c8..5e39eef71c6 100644
--- a/gdb/tui/tui.c
+++ b/gdb/tui/tui.c
@@ -394,6 +394,17 @@ gdb_getenv_term (void)
   return "<unset>";
 }
 
+/* Error out if the toplevel interpreter is not the TUI interpreter.  */
+
+static void
+require_tui_interpreter ()
+{
+  const char *interp = top_level_interpreter ()->name ();
+  if (!streq (interp, INTERP_TUI))
+    error (_("Cannot enable or disable the TUI when the interpreter is '%s'"),
+	   interp);
+}
+
 /* Enter in the tui mode (curses).
    When in normal mode, it installs the tui hooks in gdb, redirects
    the gdb output, configures the readline to work in tui mode.
@@ -424,13 +435,10 @@ tui_enable (void)
 #ifndef __MINGW32__
        const char *cap;
 #endif
-      const char *interp;
 
       /* If the top level interpreter is not the console/tui (e.g.,
 	 MI), enabling curses will certainly lose.  */
-      interp = top_level_interpreter ()->name ();
-      if (!streq (interp, INTERP_TUI))
-	error (_("Cannot enable the TUI when the interpreter is '%s'"), interp);
+      require_tui_interpreter ();
 
       /* Don't try to setup curses (and print funny control
 	 characters) if we're not outputting to a terminal.  */
@@ -556,6 +564,8 @@ tui_disable (void)
   if (!tui_active)
     return;
 
+  require_tui_interpreter ();
+
   /* Restore initial readline keymap.  */
   rl_set_keymap (tui_readline_standard_keymap);
 

base-commit: 5ae26f34ef5ac863203d63fffc968d63e823172f
-- 
2.51.0