re PR libstdc++/45628 (std::fstream::tellg invalidates I/O buffer)

2010-09-22  David Krauss  <potswa@mac.com>

	PR libstdc++/45628
	* include/bits/fstream.tcc (basic_filebuf::underflow): Add state
	transition to avoid modality requiring seekoff(0,ios::cur).
	(basic_filebuf::pbackfail): Likewise.
	(basic_filebuf::overflow): Likewise.
	(basic_filebuf::_M_seek): Avoid minor unnecessary conversion.
	(basic_filebuf::seekoff): Remove code to _M_get_ext_pos; make
	(0, ios::cur) a special case preserving buffer contents.
	(basic_filebuf::_M_get_ext_pos): New function to obtain status
	about codecvt extern_t buffer for overflow and seekoff.
	* include/std/fstream (basic_filebuf::_M_get_ext_pos): Likewise.
	* config/abi/pre/gnu.ver: Export new symbols.
	* testsuite/27_io/basic_filebuf/seekoff/char/45628-1.cc: New,
	verifies that seekoff(0, ios::cur) preserves buffers.
	* testsuite/27_io/basic_filebuf/seekoff/char/45628-2.cc: Likewise.
	for codecvt case. More lenient as it may still flush put area.
	* testsuite/27_io/basic_filebuf/seekoff/char/4.cc: Modify to
	check that seekoff is not required between read and write.
	* testsuite/27_io/basic_filebuf/seekoff/wchar_t/4.cc: Likewise.
	* testsuite/27_io/basic_filebuf/sync/wchar_t/1.cc: Remove.
	* testsuite/27_io/basic_filebuf/sync/wchar_t/1.cc: Likewise.
	* testsuite/util/testsuite_character.h (codecvt::do_length): Comply
	with 22.2.1.5.2/10 "Returns ... the LARGEST value in the range..."

From-SVN: r164529

11 files changed, 329 insertions, 141 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 8f5dc71..551b23f 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,29 @@
+2010-09-22  David Krauss  <potswa@mac.com>
+
+	PR libstdc++/45628
+	* include/bits/fstream.tcc (basic_filebuf::underflow): Add state
+	transition to avoid modality requiring seekoff(0,ios::cur).
+	(basic_filebuf::pbackfail): Likewise.
+	(basic_filebuf::overflow): Likewise.
+	(basic_filebuf::_M_seek): Avoid minor unnecessary conversion.
+	(basic_filebuf::seekoff): Remove code to _M_get_ext_pos; make
+	(0, ios::cur) a special case preserving buffer contents.
+	(basic_filebuf::_M_get_ext_pos): New function to obtain status
+	about codecvt extern_t buffer for overflow and seekoff.
+	* include/std/fstream (basic_filebuf::_M_get_ext_pos): Likewise.
+	* config/abi/pre/gnu.ver: Export new symbols.
+	* testsuite/27_io/basic_filebuf/seekoff/char/45628-1.cc: New,
+	verifies that seekoff(0, ios::cur) preserves buffers.
+	* testsuite/27_io/basic_filebuf/seekoff/char/45628-2.cc: Likewise.
+	for codecvt case. More lenient as it may still flush put area.
+	* testsuite/27_io/basic_filebuf/seekoff/char/4.cc: Modify to
+	check that seekoff is not required between read and write.
+	* testsuite/27_io/basic_filebuf/seekoff/wchar_t/4.cc: Likewise.
+	* testsuite/27_io/basic_filebuf/sync/wchar_t/1.cc: Remove.
+	* testsuite/27_io/basic_filebuf/sync/wchar_t/1.cc: Likewise.
+	* testsuite/util/testsuite_character.h (codecvt::do_length): Comply
+	with 22.2.1.5.2/10 "Returns ... the LARGEST value in the range..."
+
 2010-09-22  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* include/bits/functional_hash.h (__hash_base): Add.
diff --git a/libstdc++-v3/config/abi/pre/gnu.ver b/libstdc++-v3/config/abi/pre/gnu.ver
index 435f857..4981ca9 100644
--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -332,7 +332,13 @@ GLIBCXX_3.4 {
     # std::basic_filebuf
     _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EEC*;
     _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EED*;
-    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE[0-3]*;
+    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE0*;
+    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE13*;
+    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE15*;
+    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE16*;
+    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE19*;
+    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE2*;
+    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE3*;
     _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE4openEPKc*;
     _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE4sync*;
     _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE[5-9]*;
@@ -1178,6 +1184,9 @@ GLIBCXX_3.4.15 {
     _ZNSbIwSt11char_traitsIwESaIwEE4backEv;
     _ZNKSbIwSt11char_traitsIwESaIwEE4backEv;
 
+    # basic_filebuf::_M_get_ext_pos
+    _ZNSt13basic_filebufI[cw]St11char_traitsI[cw]EE14_M_get_ext_pos*;
+
 } GLIBCXX_3.4.14;
 
 # Symbols in the support library (libsupc++) have their own tag.
diff --git a/libstdc++-v3/include/bits/fstream.tcc b/libstdc++-v3/include/bits/fstream.tcc
index c498f48..2f661eb 100644
--- a/libstdc++-v3/include/bits/fstream.tcc
+++ b/libstdc++-v3/include/bits/fstream.tcc
@@ -1,7 +1,7 @@
 // File based streams -*- C++ -*-
 
 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
-// 2007, 2008, 2009
+// 2007, 2008, 2009, 2010
 // Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
@@ -205,8 +205,16 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
     {
       int_type __ret = traits_type::eof();
       const bool __testin = _M_mode & ios_base::in;
-      if (__testin && !_M_writing)
+      if (__testin)
 	{
+         if (_M_writing)
+           {
+             __ret = overflow();
+             if (__ret == traits_type::eof())
+               return __ret;
+             _M_set_buffer(-1);
+             _M_writing = false;
+           }
 	  // Check for pback madness, and if so switch back to the
 	  // normal buffers and jet outta here before expensive
 	  // fileops happen...
@@ -357,8 +365,16 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
     {
       int_type __ret = traits_type::eof();
       const bool __testin = _M_mode & ios_base::in;
-      if (__testin && !_M_writing)
+      if (__testin)
 	{
+         if (_M_writing)
+           {
+             __ret = overflow();
+             if (__ret == traits_type::eof())
+               return __ret;
+             _M_set_buffer(-1);
+             _M_writing = false;
+           }
 	  // Remember whether the pback buffer is active, otherwise below
 	  // we may try to store in it a second char (libstdc++/9761).
 	  const bool __testpb = _M_pback_init;
@@ -410,8 +426,16 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
       int_type __ret = traits_type::eof();
       const bool __testeof = traits_type::eq_int_type(__c, __ret);
       const bool __testout = _M_mode & ios_base::out;
-      if (__testout && !_M_reading)
+      if (__testout)
 	{
+          if (_M_reading)
+            {
+              _M_destroy_pback();
+              const int __gptr_off = _M_get_ext_pos(_M_state_last);
+              if (_M_seek(__gptr_off, ios_base::cur, _M_state_last)
+                  == pos_type(off_type(-1)))
+                return __ret;
+            }
 	  if (this->pbase() < this->pptr())
 	    {
 	      // If appropriate, append the overflow char.
@@ -691,12 +715,20 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
       if (__width < 0)
 	__width = 0;
 
-      pos_type __ret =  pos_type(off_type(-1));
+      pos_type __ret = pos_type(off_type(-1));
       const bool __testfail = __off != 0 && __width <= 0;
       if (this->is_open() && !__testfail)
 	{
+	  // tellg and tellp queries do not affect any state, unless
+	  // ! always_noconv and the put sequence is not empty.
+	  // In that case, determining the position requires converting the
+	  // put sequence. That doesn't use ext_buf, so requires a flush.
+	  bool __no_movement = __way == ios_base::cur && __off == 0
+	    && (!_M_writing || _M_codecvt->always_noconv());
+
 	  // Ditch any pback buffers to avoid confusion.
-	  _M_destroy_pback();
+	  if (!__no_movement)
+	    _M_destroy_pback();
 
 	  // Correct state at destination. Note that this is the correct
 	  // state for the current position during output, because
@@ -707,24 +739,23 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
 	  off_type __computed_off = __off * __width;
 	  if (_M_reading && __way == ios_base::cur)
 	    {
-	      if (_M_codecvt->always_noconv())
-		__computed_off += this->gptr() - this->egptr();
-	      else
+	      __state = _M_state_last;
+	      __computed_off += _M_get_ext_pos(__state);
+	    }
+	  if (!__no_movement)
+	    __ret = _M_seek(__computed_off, __way, __state);
+	  else
+	    {
+	      if (_M_writing)
+		__computed_off = this->pptr() - this->pbase();
+	      
+ 	      off_type __file_off = _M_file.seekoff(0, ios_base::cur);
+ 	      if (__file_off != off_type(-1))
 		{
-		  // Calculate offset from _M_ext_buf that corresponds
-		  // to gptr(). Note: uses _M_state_last, which
-		  // corresponds to eback().
-		  const int __gptr_off =
-		    _M_codecvt->length(_M_state_last, _M_ext_buf, _M_ext_next,
-				       this->gptr() - this->eback());
-		  __computed_off += _M_ext_buf + __gptr_off - _M_ext_end;
-
-		  // _M_state_last is modified by codecvt::length() so
-		  // it now corresponds to gptr().
-		  __state = _M_state_last;
+		  __ret = __file_off + __computed_off;
+		  __ret.state(__state);
 		}
 	    }
-	  __ret = _M_seek(__computed_off, __way, __state);
 	}
       return __ret;
     }
@@ -756,21 +787,42 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
       pos_type __ret = pos_type(off_type(-1));
       if (_M_terminate_output())
 	{
-	  // Returns pos_type(off_type(-1)) in case of failure.
-	  __ret = pos_type(_M_file.seekoff(__off, __way));
-	  if (__ret != pos_type(off_type(-1)))
+	  off_type __file_off = _M_file.seekoff(__off, __way);
+	  if (__file_off != off_type(-1))
 	    {
 	      _M_reading = false;
 	      _M_writing = false;
 	      _M_ext_next = _M_ext_end = _M_ext_buf;
 	      _M_set_buffer(-1);
 	      _M_state_cur = __state;
+	      __ret = __file_off;
 	      __ret.state(_M_state_cur);
 	    }
 	}
       return __ret;
     }
 
+  // Returns the distance from the end of the ext buffer to the point
+  // corresponding to gptr(). This is a negative value. Updates __state
+  // from eback() correspondence to gptr().
+  template<typename _CharT, typename _Traits>
+    int basic_filebuf<_CharT, _Traits>::
+    _M_get_ext_pos(__state_type& __state)
+    {
+      if (_M_codecvt->always_noconv())
+        return this->gptr() - this->egptr();
+      else
+        {
+          // Calculate offset from _M_ext_buf that corresponds to
+          // gptr(). Precondition: __state == _M_state_last, which
+          // corresponds to eback().
+          const int __gptr_off =
+            _M_codecvt->length(__state, _M_ext_buf, _M_ext_next,
+                               this->gptr() - this->eback());
+          return _M_ext_buf + __gptr_off - _M_ext_end;
+        }
+    }
+    
   template<typename _CharT, typename _Traits>
     bool
     basic_filebuf<_CharT, _Traits>::
diff --git a/libstdc++-v3/include/std/fstream b/libstdc++-v3/include/std/fstream
index 00690be..0ffd33d 100644
--- a/libstdc++-v3/include/std/fstream
+++ b/libstdc++-v3/include/std/fstream
@@ -351,9 +351,12 @@ _GLIBCXX_BEGIN_NAMESPACE(std)
       seekpos(pos_type __pos,
 	      ios_base::openmode __mode = ios_base::in | ios_base::out);
 
-      // Common code for seekoff and seekpos
+      // Common code for seekoff, seekpos, and overflow
       pos_type
       _M_seek(off_type __off, ios_base::seekdir __way, __state_type __state);
+      
+      int
+      _M_get_ext_pos(__state_type &__state);
 
       virtual int
       sync();
diff --git a/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/45628-2.cc b/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/45628-2.cc
new file mode 100644
index 0000000..6e40a89
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/45628-2.cc
@@ -0,0 +1,103 @@
+// Copyright (C) 2010 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-require-fileio "" }
+
+#include <fstream>
+#include <testsuite_hooks.h>
+#include <testsuite_character.h>
+
+const char name_01[] = "tmp_seekoff_45628.tst";
+
+unsigned underflows, overflows;
+
+class my_filebuf
+: public std::basic_filebuf<__gnu_test::pod_uchar>
+{
+  virtual int_type
+  underflow()
+  {
+    ++underflows;
+    return std::basic_filebuf<__gnu_test::pod_uchar>::underflow();
+  }
+  virtual int_type
+  overflow(int_type c)
+  {
+    ++overflows;
+    return std::basic_filebuf<__gnu_test::pod_uchar>::overflow(c);
+  }
+};
+
+// libstdc++/45628
+void test01()
+{
+  bool test __attribute__((unused)) = true;
+
+  using __gnu_test::pod_uchar;
+  std::locale loc(std::locale::classic(),
+	     new std::codecvt<my_filebuf::traits_type::char_type, char,
+	     my_filebuf::traits_type::state_type>);
+
+  my_filebuf::pos_type opos[3], ipos[3];
+  my_filebuf q;
+  q.pubimbue(loc);
+   
+  q.open(name_01, std::ios_base::in | std::ios_base::out 
+	 | std::ios_base::trunc); 
+
+  q.sputc(pod_uchar::from<char>('a'));
+  opos[0] = q.pubseekoff(0, std::ios_base::cur);
+  q.sputc(pod_uchar::from<char>('b'));
+  opos[1] = q.pubseekoff(0, std::ios_base::cur);
+  q.sputc(pod_uchar::from<char>('c'));
+  opos[2] = q.pubseekoff(0, std::ios_base::cur);
+
+  VERIFY( overflows <= 9 ); // pubseekoff calls overflow twice if converting.
+  // NB: checking opos==ipos is not very rigorous as long as it flushes, since
+  // all positions will be at initial state.
+  q.pubseekoff(0, std::ios_base::beg);
+
+  q.sbumpc();
+  VERIFY( underflows == 1 );
+
+  ipos[0] = q.pubseekoff(0, std::ios_base::cur);
+  VERIFY( ipos[0] == opos[0] );
+  q.sbumpc();
+  ipos[1] = q.pubseekoff(0, std::ios_base::cur);
+  VERIFY( ipos[1] == opos[1] );
+  q.sbumpc();
+  ipos[2] = q.pubseekoff(0, std::ios_base::cur);
+  VERIFY( ipos[2] == opos[2] );
+
+  VERIFY( underflows == 1 ); // pubseekoff never flushes get area
+  
+  // Bonus test: check automatic mode switches.
+  q.sputc(pod_uchar::from<char>('d'));
+  
+  q.pubseekpos( ipos[1] );
+  q.sputc(pod_uchar::from<char>('e'));
+  
+  VERIFY( my_filebuf::traits_type::eq(
+			my_filebuf::traits_type::to_char_type(q.sgetc()),
+			pod_uchar::from<char>('d')) );
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/char/4.cc b/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/char/4.cc
index 9422f29..fe21b3a 100644
--- a/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/char/4.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/char/4.cc
@@ -31,7 +31,7 @@ void test01()
   typedef filebuf::pos_type pos_type;
   const char name[] = "tmp_seekoff-4.tst";
 
-  const size_t size = 10;
+  const size_t size = 12;
   char buf[size];
   streamsize n;
 
@@ -46,7 +46,7 @@ void test01()
   VERIFY( n == 3 );
   VERIFY( !memcmp(buf, "abc", 3) );
 
-  fb.pubseekoff(0, ios_base::cur);
+  // Check read => write without pubseekoff(0, ios_base::cur)
 
   n = fb.sputn("ef", 2);
   VERIFY( n == 2 );
@@ -58,9 +58,17 @@ void test01()
   VERIFY( !memcmp(buf, "abcef", 5) );
 
   fb.pubseekoff(0, ios_base::beg);
-  n = fb.sputn("ghijkl", 6);
-  VERIFY( n == 6 );
+  n = fb.sputn("gh", 2);
+  VERIFY( n == 2 );
+  
+  // Check write => read without pubseekoff(0, ios_base::cur)
+
+  n = fb.sgetn( buf, 3 );
+  VERIFY( !memcmp(buf, "cef", 3) );
 
+  n = fb.sputn("ijkl", 4);
+  VERIFY( n == 4 );
+  
   fb.pubseekoff(0, ios_base::beg);
   n = fb.sgetn(buf, 2);
   VERIFY( n == 2 );
@@ -72,8 +80,8 @@ void test01()
 
   fb.pubseekoff(0, ios_base::beg);
   n = fb.sgetn(buf, size);
-  VERIFY( n == 9 );
-  VERIFY( !memcmp(buf, "ghijklmno", 9) );
+  VERIFY( n == 12 );
+  VERIFY( !memcmp(buf, "ghcefijklmno", 12) );
 
   fb.close();
 }
diff --git a/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/char/45628-1.cc b/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/char/45628-1.cc
new file mode 100644
index 0000000..a80a338
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/char/45628-1.cc
@@ -0,0 +1,79 @@
+// Copyright (C) 2010 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-require-fileio "" }
+
+#include <fstream>
+#include <testsuite_hooks.h>
+
+const char name_01[] = "tmp_seekoff_45628.tst";
+
+unsigned underflows, overflows;
+
+class my_filebuf
+: public std::filebuf
+{
+  virtual int_type
+  underflow()
+  {
+    ++underflows;
+    return std::filebuf::underflow();
+  }
+  virtual int_type
+  overflow(int_type c)
+  {
+    ++overflows;
+    return std::filebuf::overflow(c);
+  }
+};
+
+// libstdc++/45628
+void test01()
+{
+  bool test __attribute__((unused)) = true;
+
+  my_filebuf q;
+  q.open(name_01, std::ios_base::in | std::ios_base::out 
+	 | std::ios_base::trunc); 
+
+  q.sputc('a');
+  q.pubseekoff(0, std::ios_base::cur);
+  q.sputc('b');
+  q.pubseekoff(0, std::ios_base::cur);
+  q.sputc('c');
+  q.pubseekoff(0, std::ios_base::cur);
+
+  VERIFY( overflows <= 1 ); // only initial sputc allowed to overflow
+  q.pubseekoff(0, std::ios_base::beg);
+
+  q.sbumpc();
+  VERIFY( underflows == 1 );
+
+  q.pubseekoff(0, std::ios_base::cur);
+  q.sbumpc();
+  q.pubseekoff(0, std::ios_base::cur);
+  q.sbumpc();
+  q.pubseekoff(0, std::ios_base::cur);
+
+  VERIFY( underflows == 1 );
+}
+
+int main()
+{
+  test01();
+  return 0;
+}
diff --git a/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/wchar_t/4.cc b/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/wchar_t/4.cc
index 95338cf..a6bba98 100644
--- a/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/wchar_t/4.cc
+++ b/libstdc++-v3/testsuite/27_io/basic_filebuf/seekoff/wchar_t/4.cc
@@ -31,7 +31,7 @@ void test01()
   typedef wfilebuf::pos_type pos_type;
   const char name[] = "tmp_seekoff-4.tst";
 
-  const size_t size = 10;
+  const size_t size = 12;
   wchar_t buf[size];
   streamsize n;
 
@@ -46,7 +46,7 @@ void test01()
   VERIFY( n == 3 );
   VERIFY( !wmemcmp(buf, L"abc", 3) );
 
-  fb.pubseekoff(0, ios_base::cur);
+  // Check read => write without pubseekoff(0, ios_base::cur)
 
   n = fb.sputn(L"ef", 2);
   VERIFY( n == 2 );
@@ -58,8 +58,16 @@ void test01()
   VERIFY( !wmemcmp(buf, L"abcef", 5) );
 
   fb.pubseekoff(0, ios_base::beg);
-  n = fb.sputn(L"ghijkl", 6);
-  VERIFY( n == 6 );
+  n = fb.sputn(L"gh", 2);
+  VERIFY( n == 2 );
+  
+  // Check write => read without pubseekoff(0, ios_base::cur)
+
+  n = fb.sgetn( buf, 3 );
+  VERIFY( !memcmp(buf, L"cef", 3) );
+
+  n = fb.sputn(L"ijkl", 4);
+  VERIFY( n == 4 );
 
   fb.pubseekoff(0, ios_base::beg);
   n = fb.sgetn(buf, 2);
@@ -72,8 +80,8 @@ void test01()
 
   fb.pubseekoff(0, ios_base::beg);
   n = fb.sgetn(buf, size);
-  VERIFY( n == 9 );
-  VERIFY( !wmemcmp(buf, L"ghijklmno", 9) );
+  VERIFY( n == 12 );
+  VERIFY( !wmemcmp(buf, L"ghcefijklmno", 12) );
 
   fb.close();
 }
diff --git a/libstdc++-v3/testsuite/27_io/basic_filebuf/sync/char/1.cc b/libstdc++-v3/testsuite/27_io/basic_filebuf/sync/char/1.cc
deleted file mode 100644
index 0a11c43..0000000
--- a/libstdc++-v3/testsuite/27_io/basic_filebuf/sync/char/1.cc
+++ /dev/null
@@ -1,51 +0,0 @@
-// Copyright (C) 2003, 2009 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/>.
-
-// 27.8.1.4 Overridden virtual functions
-
-#include <fstream>
-#include <testsuite_hooks.h>
-
-void test01()
-{
-  using namespace std;
-
-  bool test __attribute__((unused)) = true;
-  const char* name = "tmp_sync_1";
-
-  filebuf fb;
-
-  fb.open(name, ios_base::in | ios_base::out | ios_base::trunc);
-  fb.sputn("abc", 3);
-
-  fb.pubseekoff(0, ios_base::beg);
-  fb.sputc('1');
-
-  // Sync can't be used to switch from write mode to read mode.
-  fb.pubsync();
-
-  filebuf::int_type c = fb.sbumpc();
-  VERIFY( c == filebuf::traits_type::eof() );
-
-  fb.close();
-}
-
-int main()
-{
-  test01();
-  return 0;
-}
diff --git a/libstdc++-v3/testsuite/27_io/basic_filebuf/sync/wchar_t/1.cc b/libstdc++-v3/testsuite/27_io/basic_filebuf/sync/wchar_t/1.cc
deleted file mode 100644
index a64f455..0000000
--- a/libstdc++-v3/testsuite/27_io/basic_filebuf/sync/wchar_t/1.cc
+++ /dev/null
@@ -1,51 +0,0 @@
-// Copyright (C) 2003, 2009 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/>.
-
-// 27.8.1.4 Overridden virtual functions
-
-#include <fstream>
-#include <testsuite_hooks.h>
-
-void test01()
-{
-  using namespace std;
-
-  bool test __attribute__((unused)) = true;
-  const char* name = "tmp_sync_1";
-
-  wfilebuf fb;
-
-  fb.open(name, ios_base::in | ios_base::out | ios_base::trunc);
-  fb.sputn(L"abc", 3);
-
-  fb.pubseekoff(0, ios_base::beg);
-  fb.sputc(L'1');
-
-  // Sync can't be used to switch from write mode to read mode.
-  fb.pubsync();
-
-  wfilebuf::int_type c = fb.sbumpc();
-  VERIFY( c == wfilebuf::traits_type::eof() );
-
-  fb.close();
-}
-
-int main()
-{
-  test01();
-  return 0;
-}
diff --git a/libstdc++-v3/testsuite/util/testsuite_character.h b/libstdc++-v3/testsuite/util/testsuite_character.h
index 35ccfa8..ceda1f5 100644
--- a/libstdc++-v3/testsuite/util/testsuite_character.h
+++ b/libstdc++-v3/testsuite/util/testsuite_character.h
@@ -294,7 +294,7 @@ namespace std
 		const extern_type* end, size_t max) const
       {
 	const extern_type* beg = from;
-	while (from < end && max)
+	while (from < end)
 	  {
 	    unsigned char c = *from;
 	    if (c & 0xc0)
@@ -304,6 +304,8 @@ namespace std
 		++from;
 		continue;
 	      }
+	    
+	    if (max == 0) break;
 
 	    unsigned char tmp;
 	    if (state.value & 0x8)