[gdb/tui] Delete line buffer when switching to singlekey

Say we're in TUI mode, and type "sun":
...
(gdb) sun
...

After switching to SingleKey mode using C-x s, we have just:
...
sun
...

After typing "d", we get:
...
sun
Undefined command: "sundown".  Try "help".
...

The SingleKey "d" is supposed run the "down" command.

Fix this by clearing the readline line buffer when switching to SingleKey
mode.

Tested on x86_64-linux.

PR tui/30522
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30522

Reviewed-By: Tom Tromey <tom@tromey.com>

2 files changed, 47 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.tui/single-key-2.exp b/gdb/testsuite/gdb.tui/single-key-2.exp
new file mode 100644
index 0000000..5bde522
--- /dev/null
+++ b/gdb/testsuite/gdb.tui/single-key-2.exp
@@ -0,0 +1,40 @@
+# Copyright 2023 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/>.
+
+tuiterm_env
+
+Term::clean_restart 24 80
+if {![Term::enter_tui]} {
+    unsupported "TUI not supported"
+    return
+}
+
+set command_win { 0 16 80 8 }
+
+# Send some chars as a partial command.
+send_gdb "sun"
+gdb_assert { [Term::wait_for_region_contents 0 16 80 8 "$gdb_prompt sun"] } \
+    "got sun"
+
+# Enter single-key mode.  That should clear the partial command.
+send_gdb "\030s"
+
+# Send "down command".
+send_gdb "d"
+
+# Regression test for PR tui/30522.  Make sure we issue the command "down"
+# rather than "sundown".
+gdb_assert { [Term::wait_for_region_contents {*}$command_win "No stack\\."] } \
+    "down using single-key after partial command"
diff --git a/gdb/tui/tui.c b/gdb/tui/tui.c
index 373d167..43be816 100644
--- a/gdb/tui/tui.c
+++ b/gdb/tui/tui.c
@@ -252,6 +252,13 @@ tui_rl_next_keymap (int notused1, int notused2)
   if (!tui_active)
     tui_rl_switch_mode (0 /* notused */, 0 /* notused */);
 
+  if (rl_end)
+    {
+      rl_end = 0;
+      rl_point = 0;
+      rl_mark = 0;
+    }
+
   tui_set_key_mode (tui_current_key_mode == TUI_COMMAND_MODE
 		    ? TUI_SINGLE_KEY_MODE : TUI_COMMAND_MODE);
   return 0;