Strip trailing newlines from input string

A co-worker noticed a strange situation where "target remote" would
fail due to a trailing newline in the address part of the command.
Eventually he tracked this down to the fact that he was pasting the
command into the terminal, and due to bracketed paste mode, the
newline was being preserved by readline.

It seems to me that we basically never want a trailing newline on a
gdb command, so this patch removes it when handling the readline
result.

Co-Authored-By: Kévin Le Gouguec <legouguec@adacore.com>
Approved-By: Luis Machado <luis.machado@arm.com>
Tested-By: Luis Machado <luis.machado@arm.com>

gdb/event-top.c

@@ -251,6 +251,14 @@ gdb_rl_callback_handler (char *rl) noexcept
   static struct gdb_exception gdb_rl_expt;
   struct ui *ui = current_ui;
 
+  /* In bracketed paste mode, pasting a complete line can result in a
+     literal newline appearing at the end of LINE.  However, we never
+     want this in gdb.  */
+  size_t len = strlen (rl);
+  while (len > 0 && (rl[len - 1] == '\r' || rl[len - 1] == '\n'))
+    --len;
+  rl[len] = '\0';
+
   try
     {
       /* Ensure the exception is reset on each call.  */

gdb/testsuite/gdb.base/paste-newline.exp

@@ -0,0 +1,45 @@
+# Copyright (C) 2024 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/>.
+
+# This test script checks that a trailing newline is stripped from a
+# bracketed paste.
+
+save_vars { env(TERM) env(INPUTRC) } {
+    setenv TERM ansi
+
+    # Create an inputrc file that enables bracketed paste mode.
+    set inputrc [standard_output_file inputrc]
+    set fd [open "$inputrc" w]
+    puts $fd "set enable-bracketed-paste on"
+    close $fd
+
+    setenv INPUTRC "$inputrc"
+
+    clean_restart
+
+    send_gdb "\033\[200~echo hello\n\033\[201~\n"
+
+    gdb_test_multiple "" "newline removed from paste" {
+	-re ".*echo hello.*hello\[^\n\]*$gdb_prompt $" {
+	    # Some escape sequences are expected between echo's output
+	    # and the prompt (e.g. the paste-bracketing toggle
+	    # sequences) but _newlines_ are not.
+	    pass $gdb_test_name
+	}
+	-re ".*echo hello.*hello.*\r\n.*$gdb_prompt $" {
+	    fail $gdb_test_name
+	}
+    }
+}