[Patch] To filebuf::underflow vs codecvt::in

[Paolo Carlini <pcarlini at suse dot de>]

Hi,

this issue has been reported to the Novell Bugzilla: the fix seems easy, 
just don't call codecvt::in when eof is reached and there are no chars 
to convert. Apparently this kind of behavior can be seen also in other 
implementations. Tested x86-linux, will wait till the endo of today 
before committing to mainline.

Paolo.

///////////////
2007-03-27  Paolo Carlini  <pcarlini@suse.de>

	* include/bits/fstream.tcc (basic_filebuf<>::underflow):
	Don't call codecvt::in at all if _M_ext_next >= _M_ext_end.
	* testsuite/27_io/basic_filebuf/underflow/char/3.cc: New.

Index: include/bits/fstream.tcc
===================================================================
--- include/bits/fstream.tcc	(revision 123204)
+++ include/bits/fstream.tcc	(working copy)
@@ -279,16 +279,19 @@
 		      _M_ext_end += __elen;
 		    }
 
-		  char_type* __iend;
-		  __r = _M_codecvt->in(_M_state_cur, _M_ext_next,
-				       _M_ext_end, _M_ext_next, this->eback(),
-				       this->eback() + __buflen, __iend);
+		  char_type* __iend = this->eback();
+		  if (_M_ext_next < _M_ext_end)
+		    __r = _M_codecvt->in(_M_state_cur, _M_ext_next,
+					 _M_ext_end, _M_ext_next,
+					 this->eback(),
+					 this->eback() + __buflen, __iend);
 		  if (__r == codecvt_base::noconv)
 		    {
 		      size_t __avail = _M_ext_end - _M_ext_buf;
 		      __ilen = std::min(__avail, __buflen);
 		      traits_type::copy(this->eback(),
-					reinterpret_cast<char_type*>(_M_ext_buf), __ilen);
+					reinterpret_cast<char_type*>
+					(_M_ext_buf), __ilen);
 		      _M_ext_next = _M_ext_buf + __ilen;
 		    }
 		  else
Index: testsuite/27_io/basic_filebuf/underflow/char/3.cc
===================================================================
--- testsuite/27_io/basic_filebuf/underflow/char/3.cc	(revision 0)
+++ testsuite/27_io/basic_filebuf/underflow/char/3.cc	(revision 0)
@@ -0,0 +1,85 @@
+// Copyright (C) 2007 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 2, 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 COPYING.  If not, write to the Free
+// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+// USA.
+
+// 27.8.1.4 Overridden virtual functions
+
+// { dg-require-fileio "" }
+
+#include <fstream>
+#include <cctype>
+#include <locale>
+#include <testsuite_hooks.h>
+
+class Mycvtcc
+: public std::codecvt<char, char, std::mbstate_t>
+{
+protected:
+  virtual result
+  do_in(state_type&,
+	const extern_type* from, const extern_type* from_end,
+	const extern_type*& from_next,
+	intern_type* to, intern_type* to_limit,
+	intern_type*& to_next) const
+  {
+    from_next = from, to_next = to;
+    
+    if (from_next == from_end || to_next == to_limit)
+      return partial;
+    
+    if (std::islower(*from_next))
+      *to_next = std::toupper(*from_next);
+    else
+      *to_next = *from_next;
+    ++from_next, ++to_next;
+    return ok;
+  }
+
+  virtual bool
+  do_always_noconv() const throw()
+  { return false; }
+};
+
+// See Novell Bug 255122
+void test01()
+{
+  bool test __attribute__((unused)) = true;
+  using namespace std;
+
+  const char* name = "tmp_underflow_3.tst";
+  filebuf fbuf, fbufx;
+
+  fbuf.open(name, ios_base::out | ios_base::trunc);
+  VERIFY( fbuf.sputc('a') == 'a' );
+  VERIFY( fbuf.sputc('b') == 'b' );
+  VERIFY( fbuf.sputc('\n') == '\n' );
+  fbuf.close();
+
+  fbufx.pubimbue(locale(locale::classic(), new Mycvtcc));
+  fbufx.open(name, ios_base::in);
+  VERIFY( fbufx.sbumpc() == 'A' );
+  VERIFY( fbufx.sbumpc() == 'B' );
+  VERIFY( fbufx.sbumpc() == '\n' );
+  VERIFY( fbufx.sbumpc() == filebuf::traits_type::eof() );
+  fbufx.close();
+}
+
+int main()
+{
+  test01();
+  return 0;
+}