gdb: add operator+= and operator+ overload for std::string

This commit adds operator+= and operator+ overloads for adding
gdb::unique_xmalloc_ptr<char> to a std::string.  I could only find 3
places in GDB where this was useful right now, and these all make use
of operator+=.

I've also added a self test for gdb::unique_xmalloc_ptr<char>, which
makes use of both operator+= and operator+, so they are both getting
used/tested.

There should be no user visible changes after this commit, except when
running 'maint selftest', where the new self test is visible.

1 files changed, 57 insertions, 0 deletions

diff --git a/gdb/unittests/unique_xmalloc_ptr_char.c b/gdb/unittests/unique_xmalloc_ptr_char.c
new file mode 100644
index 0000000..3eb1b7b
--- /dev/null
+++ b/gdb/unittests/unique_xmalloc_ptr_char.c
@@ -0,0 +1,57 @@
+/* Self tests for gdb::unique_xmalloc_ptr<char>.
+
+   Copyright (C) 2022 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/>.  */
+
+#include "defs.h"
+#include "gdbsupport/selftest.h"
+#include "selftest-arch.h"
+#include "gdbsupport/gdb_unique_ptr.h"
+
+namespace selftests {
+namespace unpack {
+
+static void
+unique_xmalloc_ptr_char ()
+{
+  gdb::unique_xmalloc_ptr<char> a = make_unique_xstrdup ("abc");
+  gdb::unique_xmalloc_ptr<char> b = make_unique_xstrndup ("defghi", 3);
+
+  SELF_CHECK (strcmp (a.get (), "abc") == 0);
+  SELF_CHECK (strcmp (b.get (), "def") == 0);
+
+  std::string str = "xxx";
+
+  /* Check the operator+= overload.  */
+  str += a;
+  SELF_CHECK (str == "xxxabc");
+
+  /* Check the operator+ overload.  */
+  str = str + b;
+  SELF_CHECK (str == "xxxabcdef");
+}
+
+}
+}
+
+void _initialize_unique_xmalloc_ptr_char ();
+void
+_initialize_unique_xmalloc_ptr_char ()
+{
+  selftests::register_test ("unique_xmalloc_ptr_char",
+			    selftests::unpack::unique_xmalloc_ptr_char);
+}