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.

gdb/ChangeLog

@@ -1,3 +1,13 @@
+2018-05-17  Simon Marchi  <simon.marchi@ericsson.com>
+
+	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.
+
 2018-05-17  Tom Tromey  <tom@tromey.com>
 
 	PR symtab/23010:

gdb/Makefile.in

@@ -418,6 +418,7 @@ SUBDIR_UNITTESTS_SRCS = \
 	unittests/array-view-selftests.c \
 	unittests/common-utils-selftests.c \
 	unittests/environ-selftests.c \
+	unittests/format_pieces-selftests.c \
 	unittests/function-view-selftests.c \
 	unittests/lookup_name_info-selftests.c \
 	unittests/memory-map-selftests.c \

gdb/common/format.c

@@ -56,6 +56,9 @@ format_pieces::format_pieces (const char **arg)
 	    case 'b':
 	      *f++ = '\b';
 	      break;
+	    case 'e':
+	      *f++ = '\e';
+	      break;
 	    case 'f':
 	      *f++ = '\f';
 	      break;

gdb/common/format.h

@@ -20,6 +20,8 @@
 #ifndef COMMON_FORMAT_H
 #define COMMON_FORMAT_H
 
+#include "common/gdb_string_view.h"
+
 #if defined(__MINGW32__) && !defined(PRINTF_HAS_LONG_LONG)
 # define USE_PRINTF_I64 1
 # define PRINTF_HAS_LONG_LONG
@@ -54,6 +56,12 @@ struct format_piece
   {
   }
 
+  bool operator== (const format_piece &other) const
+  {
+    return (this->argclass == other.argclass
+	    && gdb::string_view (this->string) == other.string);
+  }
+
   const char *string;
   enum argclass argclass;
 };
@@ -67,11 +75,6 @@ public:
 
   DISABLE_COPY_AND_ASSIGN (format_pieces);
 
-  format_piece &operator[] (size_t index)
-  {
-    return m_pieces[index];
-  }
-
   typedef std::vector<format_piece>::iterator iterator;
 
   iterator begin ()

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);
+}