Make format_pieces recognize the \e escape sequence

I noticed that the printf command did not recognize the \e escape
sequence, used amongst other things to use colors:

  (gdb) printf "This is \e[32mgreen\e[m!\n"
  Unrecognized escape character \e in format string.

This patch makes format_pieces recognize it, which makes that command
print the expected result in glorious color.

I wrote a really simple unit test for format_pieces.
format_pieces::operator[] is unused so I removed it.  I added
format_piece::operator==, which is needed to compare vectors of
format_piece.

gdb/ChangeLog:

	PR cli/14975
	* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add
	unittests/format_pieces-selftests.c.
	* common/format.h (format_piece) <operator==>: New.
	(format_pieces) <operator[]>: Remove.
	* common/format.c (format_pieces::format_pieces): Handle \e.
	* unittests/format_pieces-selftests.c: New.

1 files changed, 76 insertions, 0 deletions

diff --git a/gdb/unittests/format_pieces-selftests.c b/gdb/unittests/format_pieces-selftests.c
new file mode 100644
index 0000000..6d11a9c
--- /dev/null
+++ b/gdb/unittests/format_pieces-selftests.c
@@ -0,0 +1,76 @@
+/* Self tests for format_pieces for GDB, the GNU debugger.
+
+   Copyright (C) 2018 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 "common/format.h"
+#include "common/selftest.h"
+
+namespace selftests {
+namespace format_pieces {
+
+/* Verify that parsing STR gives pieces equal to EXPECTED_PIECES.  */
+
+static void
+check (const char *str, const std::vector<format_piece> &expected_pieces)
+{
+  ::format_pieces pieces (&str);
+
+  SELF_CHECK ((pieces.end () - pieces.begin ()) == expected_pieces.size ());
+  SELF_CHECK (std::equal (pieces.begin (), pieces.end (),
+			  expected_pieces.begin ()));
+}
+
+static void
+test_escape_sequences ()
+{
+  check ("This is an escape sequence: \\e",
+    {
+      format_piece ("This is an escape sequence: \e", literal_piece),
+    });
+}
+
+static void
+test_format_specifier ()
+{
+  check ("Hello %d%llx%%d",
+    {
+      format_piece ("Hello ", literal_piece),
+      format_piece ("%d", int_arg),
+      format_piece ("", literal_piece),
+      format_piece ("%llx", long_long_arg),
+      format_piece ("%%d", literal_piece),
+    });
+}
+
+static void
+run_tests ()
+{
+  test_escape_sequences ();
+  test_format_specifier ();
+}
+
+} /* namespace format_pieces */
+} /* namespace selftests */
+
+void
+_initialize_format_pieces_selftests ()
+{
+  selftests::register_test ("format_pieces",
+			    selftests::format_pieces::run_tests);
+}