gdb/python: add gdb.host_charset function

We already have gdb.target_charset and gdb.target_wide_charset.  This
commit adds gdb.host_charset along the same lines.

gdb/NEWS

@@ -143,6 +143,9 @@ show debug lin-lwp
      is equivalent to the existing 'maint packet' CLI command; it
      allows a user specified packet to be sent to the remote target.
 
+  ** New function gdb.host_charset(), returns a string, which is the
+     name of the current host charset.
+
 * New features in the GDB remote stub, GDBserver
 
   ** GDBserver is now supported on OpenRISC GNU/Linux.

gdb/doc/python.texi

@@ -518,6 +518,14 @@ Return the name of the current target wide character set
 never returned.
 @end defun
 
+@findex gdb.host_charset
+@defun gdb.host_charset ()
+Return a string, the name of the current host character set
+(@pxref{Character Sets}).  This differs from
+@code{gdb.parameter('host-charset')} in that @samp{auto} is never
+returned.
+@end defun
+
 @findex gdb.solib_name
 @defun gdb.solib_name (address)
 Return the name of the shared library holding the given @var{address}

gdb/python/python.c

@@ -571,6 +571,16 @@ gdbpy_target_wide_charset (PyObject *self, PyObject *args)
   return PyUnicode_Decode (cset, strlen (cset), host_charset (), NULL);
 }
 
+/* Implement gdb.host_charset().  */
+
+static PyObject *
+gdbpy_host_charset (PyObject *self, PyObject *args)
+{
+  const char *cset = host_charset ();
+
+  return PyUnicode_Decode (cset, strlen (cset), host_charset (), NULL);
+}
+
 /* A Python function which evaluates a string using the gdb CLI.  */
 
 static PyObject *
@@ -2281,6 +2291,9 @@ Return the name of the current target charset." },
   { "target_wide_charset", gdbpy_target_wide_charset, METH_NOARGS,
     "target_wide_charset () -> string.\n\
 Return the name of the current target wide charset." },
+  { "host_charset", gdbpy_host_charset, METH_NOARGS,
+    "host_charset () -> string.\n\
+Return the name of the current host charset." },
   { "rbreak", (PyCFunction) gdbpy_rbreak, METH_VARARGS | METH_KEYWORDS,
     "rbreak (Regex) -> List.\n\
 Return a Tuple containing gdb.Breakpoint objects that match the given Regex." },

gdb/testsuite/gdb.python/py-charset.exp

@@ -0,0 +1,50 @@
+# Copyright 2022 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/>.
+
+load_lib gdb-python.exp
+
+gdb_exit
+gdb_start
+
+# Skip all tests if Python scripting is not enabled.
+if { [skip_python_tests] } { continue }
+
+# Each test data has 4 parts:
+# 1. The string used in 'show XXX-charset' command,
+# 2. The string expected in the output of the command used in #1,
+# 3. The string used is gdb.XXXX_charset() python function call,
+# 4. A string that is a regexp appended to the result of #1, used to
+#    match the output of #3
+foreach test_data { {host host host ""} \
+			{target target target ""} \
+			{target-wide "target wide" \
+			     "target_wide" "(LE|BE)?"} } {
+    with_test_prefix "charset=[lindex $test_data 0]" {
+	set charset "unknown"
+	gdb_test_multiple "show [lindex $test_data 0]-charset" "" {
+	    -re "The [lindex $test_data 1] character set is \"auto; currently (\[^\"\]*)\".*$gdb_prompt $" {
+		set charset $expect_out(1,string)
+		pass $gdb_test_name
+	    }
+	    -re "The [lindex $test_data 1] character set is \"(\[^\"\]*)\".*$gdb_prompt $" {
+		set charset $expect_out(1,string)
+		pass $gdb_test_name
+	    }
+	}
+	set charset "${charset}[lindex $test_data 3]"
+	gdb_test "python print(gdb.[lindex $test_data 2]_charset())" \
+	    "${charset}"
+    }
+}