Fix encoding() and max_length() values for codecvt facets

	* src/c++11/codecvt.cc (codecvt<char16_t, char, mbstate_t>)
	(codecvt<char32_t, char, mbstate_t>, __codecvt_utf8_base<char16_t>)
	(__codecvt_utf8_base<char32_t>, __codecvt_utf8_base<wchar_t>)
	(__codecvt_utf16_base<char16_t>, __codecvt_utf16_base<char32_t>)
	(__codecvt_utf16_base<wchar_t>, __codecvt_utf8_utf16_base<char16_t>)
	(__codecvt_utf8_utf16_base<char32_t>)
	(__codecvt_utf8_utf16_base<wchar_t>): Fix do_encoding() and
	do_max_length() return values.
	* testsuite/22_locale/codecvt/codecvt_utf16/members.cc: New test.
	* testsuite/22_locale/codecvt/codecvt_utf8/members.cc: New test.
	* testsuite/22_locale/codecvt/codecvt_utf8_utf16/members.cc: New test.

From-SVN: r246201

6 files changed, 341 insertions, 33 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 83f74ef..9facce8 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,17 @@
 2017-03-16  Jonathan Wakely  <jwakely@redhat.com>
 
+	* src/c++11/codecvt.cc (codecvt<char16_t, char, mbstate_t>)
+	(codecvt<char32_t, char, mbstate_t>, __codecvt_utf8_base<char16_t>)
+	(__codecvt_utf8_base<char32_t>, __codecvt_utf8_base<wchar_t>)
+	(__codecvt_utf16_base<char16_t>, __codecvt_utf16_base<char32_t>)
+	(__codecvt_utf16_base<wchar_t>, __codecvt_utf8_utf16_base<char16_t>)
+	(__codecvt_utf8_utf16_base<char32_t>)
+	(__codecvt_utf8_utf16_base<wchar_t>): Fix do_encoding() and
+	do_max_length() return values.
+	* testsuite/22_locale/codecvt/codecvt_utf16/members.cc: New test.
+	* testsuite/22_locale/codecvt/codecvt_utf8/members.cc: New test.
+	* testsuite/22_locale/codecvt/codecvt_utf8_utf16/members.cc: New test.
+
 	PR libstdc++/79980
 	* include/bits/locale_conv.h (__do_str_codecvt): Set __count on
 	error path.
diff --git a/libstdc++-v3/src/c++11/codecvt.cc b/libstdc++-v3/src/c++11/codecvt.cc
index a50804c..9c91725 100644
--- a/libstdc++-v3/src/c++11/codecvt.cc
+++ b/libstdc++-v3/src/c++11/codecvt.cc
@@ -72,8 +72,8 @@ namespace
 
   // Multibyte sequences can have "header" consisting of Byte Order Mark
   const unsigned char utf8_bom[3] = { 0xEF, 0xBB, 0xBF };
-  const unsigned char utf16_bom[4] = { 0xFE, 0xFF };
-  const unsigned char utf16le_bom[4] = { 0xFF, 0xFE };
+  const unsigned char utf16_bom[2] = { 0xFE, 0xFF };
+  const unsigned char utf16le_bom[2] = { 0xFF, 0xFE };
 
   template<size_t N>
     inline bool
@@ -695,7 +695,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 codecvt<char16_t, char, mbstate_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-8 is not a fixed-width encoding
 
 bool
 codecvt<char16_t, char, mbstate_t>::do_always_noconv() const throw()
@@ -713,9 +713,9 @@ do_length(state_type&, const extern_type* __from,
 int
 codecvt<char16_t, char, mbstate_t>::do_max_length() const throw()
 {
-  // Any valid UTF-8 sequence of 3 bytes fits in a single 16-bit code unit,
-  // whereas 4 byte sequences require two 16-bit code units.
-  return 3;
+  // A single character (one or two UTF-16 code units) requires
+  // up to four UTF-8 code units.
+  return 4;
 }
 
 // Define members of codecvt<char32_t, char, mbstate_t> specialization.
@@ -766,7 +766,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 codecvt<char32_t, char, mbstate_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-8 is not a fixed-width encoding
 
 bool
 codecvt<char32_t, char, mbstate_t>::do_always_noconv() const throw()
@@ -783,7 +783,11 @@ do_length(state_type&, const extern_type* __from,
 
 int
 codecvt<char32_t, char, mbstate_t>::do_max_length() const throw()
-{ return 4; }
+{
+  // A single character (one UTF-32 code unit) requires
+  // up to 4 UTF-8 code units.
+  return 4;
+}
 
 // Define members of codecvt_utf8<char16_t> base class implementation.
 // Converts from UTF-8 to UCS-2.
@@ -835,7 +839,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf8_base<char16_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-8 is not a fixed-width encoding
 
 bool
 __codecvt_utf8_base<char16_t>::do_always_noconv() const throw()
@@ -852,7 +856,14 @@ do_length(state_type&, const extern_type* __from,
 
 int
 __codecvt_utf8_base<char16_t>::do_max_length() const throw()
-{ return 3; }
+{
+  // A single UCS-2 character requires up to three UTF-8 code units.
+  // (UCS-2 cannot represent characters that use four UTF-8 code units).
+  int max = 3;
+  if (_M_mode & consume_header)
+    max += sizeof(utf8_bom);
+  return max;
+}
 
 // Define members of codecvt_utf8<char32_t> base class implementation.
 // Converts from UTF-8 to UTF-32 (aka UCS-4).
@@ -900,7 +911,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf8_base<char32_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-8 is not a fixed-width encoding
 
 bool
 __codecvt_utf8_base<char32_t>::do_always_noconv() const throw()
@@ -917,7 +928,13 @@ do_length(state_type&, const extern_type* __from,
 
 int
 __codecvt_utf8_base<char32_t>::do_max_length() const throw()
-{ return 4; }
+{
+  // A single UCS-4 character requires up to four UTF-8 code units.
+  int max = 4;
+  if (_M_mode & consume_header)
+    max += sizeof(utf8_bom);
+  return max;
+}
 
 #ifdef _GLIBCXX_USE_WCHAR_T
 // Define members of codecvt_utf8<wchar_t> base class implementation.
@@ -992,7 +1009,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf8_base<wchar_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-8 is not a fixed-width encoding
 
 bool
 __codecvt_utf8_base<wchar_t>::do_always_noconv() const throw()
@@ -1015,7 +1032,16 @@ do_length(state_type&, const extern_type* __from,
 
 int
 __codecvt_utf8_base<wchar_t>::do_max_length() const throw()
-{ return 4; }
+{
+#if __SIZEOF_WCHAR_T__ == 2
+  int max = 3; // See __codecvt_utf8_base<char16_t>::do_max_length()
+#else
+  int max = 4; // See __codecvt_utf8_base<char32_t>::do_max_length()
+#endif
+  if (_M_mode & consume_header)
+    max += sizeof(utf8_bom);
+  return max;
+}
 #endif
 
 // Define members of codecvt_utf16<char16_t> base class implementation.
@@ -1070,7 +1096,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf16_base<char16_t>::do_encoding() const throw()
-{ return 1; }
+{ return 0; } // UTF-16 is not a fixed-width encoding
 
 bool
 __codecvt_utf16_base<char16_t>::do_always_noconv() const throw()
@@ -1089,7 +1115,14 @@ do_length(state_type&, const extern_type* __from,
 
 int
 __codecvt_utf16_base<char16_t>::do_max_length() const throw()
-{ return 3; }
+{
+  // A single UCS-2 character requires one UTF-16 code unit (so two chars).
+  // (UCS-2 cannot represent characters that use multiple UTF-16 code units).
+  int max = 2;
+  if (_M_mode & consume_header)
+    max += sizeof(utf16_bom);
+  return max;
+}
 
 // Define members of codecvt_utf16<char32_t> base class implementation.
 // Converts from UTF-16 to UTF-32 (aka UCS-4).
@@ -1143,7 +1176,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf16_base<char32_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-16 is not a fixed-width encoding
 
 bool
 __codecvt_utf16_base<char32_t>::do_always_noconv() const throw()
@@ -1162,7 +1195,14 @@ do_length(state_type&, const extern_type* __from,
 
 int
 __codecvt_utf16_base<char32_t>::do_max_length() const throw()
-{ return 4; }
+{
+  // A single UCS-4 character requires one or two UTF-16 code units
+  // (so up to four chars).
+  int max = 4;
+  if (_M_mode & consume_header)
+    max += sizeof(utf16_bom);
+  return max;
+}
 
 #ifdef _GLIBCXX_USE_WCHAR_T
 // Define members of codecvt_utf16<wchar_t> base class implementation.
@@ -1237,7 +1277,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf16_base<wchar_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-16 is not a fixed-width encoding
 
 bool
 __codecvt_utf16_base<wchar_t>::do_always_noconv() const throw()
@@ -1261,7 +1301,16 @@ do_length(state_type&, const extern_type* __from,
 
 int
 __codecvt_utf16_base<wchar_t>::do_max_length() const throw()
-{ return 4; }
+{
+#if __SIZEOF_WCHAR_T__ == 2
+  int max = 2; // See __codecvt_utf16_base<char16_t>::do_max_length()
+#else
+  int max = 4; // See __codecvt_utf16_base<char32_t>::do_max_length()
+#endif
+  if (_M_mode & consume_header)
+    max += sizeof(utf16_bom);
+  return max;
+}
 #endif
 
 // Define members of codecvt_utf8_utf16<char16_t> base class implementation.
@@ -1314,7 +1363,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf8_utf16_base<char16_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-8 is not a fixed-width encoding
 
 bool
 __codecvt_utf8_utf16_base<char16_t>::do_always_noconv() const throw()
@@ -1332,9 +1381,12 @@ do_length(state_type&, const extern_type* __from,
 int
 __codecvt_utf8_utf16_base<char16_t>::do_max_length() const throw()
 {
-  // Any valid UTF-8 sequence of 3 bytes fits in a single 16-bit code unit,
-  // whereas 4 byte sequences require two 16-bit code units.
-  return 3;
+  // A single character can be 1 or 2 UTF-16 code units,
+  // requiring up to 4 UTF-8 code units.
+  int max = 4;
+  if (_M_mode & consume_header)
+    max += sizeof(utf8_bom);
+  return max;
 }
 
 // Define members of codecvt_utf8_utf16<char32_t> base class implementation.
@@ -1387,7 +1439,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf8_utf16_base<char32_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-8 is not a fixed-width encoding
 
 bool
 __codecvt_utf8_utf16_base<char32_t>::do_always_noconv() const throw()
@@ -1405,9 +1457,12 @@ do_length(state_type&, const extern_type* __from,
 int
 __codecvt_utf8_utf16_base<char32_t>::do_max_length() const throw()
 {
-  // Any valid UTF-8 sequence of 3 bytes fits in a single 16-bit code unit,
-  // whereas 4 byte sequences require two 16-bit code units.
-  return 3;
+  // A single character can be 1 or 2 UTF-16 code units,
+  // requiring up to 4 UTF-8 code units.
+  int max = 4;
+  if (_M_mode & consume_header)
+    max += sizeof(utf8_bom);
+  return max;
 }
 
 #ifdef _GLIBCXX_USE_WCHAR_T
@@ -1461,7 +1516,7 @@ do_in(state_type&, const extern_type* __from, const extern_type* __from_end,
 
 int
 __codecvt_utf8_utf16_base<wchar_t>::do_encoding() const throw()
-{ return 0; }
+{ return 0; } // UTF-8 is not a fixed-width encoding
 
 bool
 __codecvt_utf8_utf16_base<wchar_t>::do_always_noconv() const throw()
@@ -1479,9 +1534,12 @@ do_length(state_type&, const extern_type* __from,
 int
 __codecvt_utf8_utf16_base<wchar_t>::do_max_length() const throw()
 {
-  // Any valid UTF-8 sequence of 3 bytes fits in a single 16-bit code unit,
-  // whereas 4 byte sequences require two 16-bit code units.
-  return 3;
+  // A single character can be 1 or 2 UTF-16 code units,
+  // requiring up to 4 UTF-8 code units.
+  int max = 4;
+  if (_M_mode & consume_header)
+    max += sizeof(utf8_bom);
+  return max;
 }
 #endif
 
diff --git a/libstdc++-v3/testsuite/22_locale/codecvt/char16_t.cc b/libstdc++-v3/testsuite/22_locale/codecvt/char16_t.cc
index b40fc65..3288e77 100644
--- a/libstdc++-v3/testsuite/22_locale/codecvt/char16_t.cc
+++ b/libstdc++-v3/testsuite/22_locale/codecvt/char16_t.cc
@@ -34,7 +34,7 @@ test01()
   const codecvt_c16* const cvt = &use_facet<codecvt_c16>(loc_c);
 
   VERIFY(!cvt->always_noconv());
-  VERIFY(cvt->max_length() == 3);
+  VERIFY(cvt->max_length() == 4);
   VERIFY(cvt->encoding() == 0);
 
   const char u8dat[] = u8"H\U000000E4ll\U000000F6 \U0001F63F \U000056FD "
diff --git a/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf16/members.cc b/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf16/members.cc
new file mode 100644
index 0000000..993c860
--- /dev/null
+++ b/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf16/members.cc
@@ -0,0 +1,81 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library 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, or (at your option)
+// any later version.
+
+// This library 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 library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target c++11 } }
+
+#include <codecvt>
+#include <testsuite_hooks.h>
+
+const int bomlen = 2; // UTF-16 BOM is 16 bits
+
+void
+test01()
+{
+  const int maxlen = 2;
+
+  std::codecvt_utf16<char16_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf16<char16_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+}
+
+void
+test02()
+{
+  const int maxlen = 4;
+
+  std::codecvt_utf16<char32_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf16<char32_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+}
+
+void
+test03()
+{
+#ifdef _GLIBCXX_USE_WCHAR_T
+  const int maxlen = sizeof(wchar_t) == 4 ? 4 : 2;
+
+  std::codecvt_utf16<wchar_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf16<wchar_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+#endif
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+}
diff --git a/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf8/members.cc b/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf8/members.cc
new file mode 100644
index 0000000..baeb049
--- /dev/null
+++ b/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf8/members.cc
@@ -0,0 +1,81 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library 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, or (at your option)
+// any later version.
+
+// This library 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 library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target c++11 } }
+
+#include <codecvt>
+#include <testsuite_hooks.h>
+
+const int bomlen = 3; // UTF-8 BOM is 24 bits
+
+void
+test01()
+{
+  const int maxlen = 3;
+
+  std::codecvt_utf8<char16_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf8<char16_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+}
+
+void
+test02()
+{
+  const int maxlen = 4;
+
+  std::codecvt_utf8<char32_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf8<char32_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+}
+
+void
+test03()
+{
+#ifdef _GLIBCXX_USE_WCHAR_T
+  const int maxlen = sizeof(wchar_t) == 4 ? 4 : 3;
+
+  std::codecvt_utf8<wchar_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf8<wchar_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+#endif
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+}
diff --git a/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf8_utf16/members.cc b/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf8_utf16/members.cc
new file mode 100644
index 0000000..8fcdfff
--- /dev/null
+++ b/libstdc++-v3/testsuite/22_locale/codecvt/codecvt_utf8_utf16/members.cc
@@ -0,0 +1,76 @@
+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library 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, or (at your option)
+// any later version.
+
+// This library 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 library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target c++11 } }
+
+#include <codecvt>
+#include <testsuite_hooks.h>
+
+const int bomlen = 3; // UTF-8 BOM is 24 bits
+const int maxlen = 4;
+
+void
+test01()
+{
+  std::codecvt_utf8_utf16<char16_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf8_utf16<char16_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+}
+
+void
+test02()
+{
+  std::codecvt_utf8_utf16<char32_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf8_utf16<char32_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+}
+
+void
+test03()
+{
+#ifdef _GLIBCXX_USE_WCHAR_T
+  std::codecvt_utf8_utf16<wchar_t> c;
+  VERIFY( c.always_noconv() == false );
+  VERIFY( c.encoding() == 0 );
+  VERIFY( c.max_length() == maxlen );
+
+  std::codecvt_utf8_utf16<wchar_t, 0x10ffff, std::consume_header> c_bom;
+  VERIFY( c_bom.always_noconv() == false );
+  VERIFY( c_bom.encoding() == 0 );
+  VERIFY( c_bom.max_length() == (maxlen + bomlen) );
+#endif
+}
+
+int
+main()
+{
+  test01();
+  test02();
+  test03();
+}