re PR libstdc++/9761 (filebuf::pbackfail discards previously put back characters)

2003-06-02  Paolo Carlini  <pcarlini@unitus.it>

	PR libstdc++/9761
	* include/bits/fstream.tcc (pbackfail): If the pback buffer
	is already active don't try to store in it a second char.
	* testsuite/27_io/basic_filebuf/pbackfail/char/9761.cc: New.

	* include/bits/fstream.tcc (pbackfail): Add unbuffered bits.

From-SVN: r67337

3 files changed, 94 insertions, 45 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 60347aa..cac15bb 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,14 @@
 2003-06-02  Paolo Carlini  <pcarlini@unitus.it>
 
+	PR libstdc++/9761
+	* include/bits/fstream.tcc (pbackfail): If the pback buffer
+	is already active don't try to store in it a second char.
+	* testsuite/27_io/basic_filebuf/pbackfail/char/9761.cc: New.
+
+	* include/bits/fstream.tcc (pbackfail): Add unbuffered bits.
+
+2003-06-02  Paolo Carlini  <pcarlini@unitus.it>
+
 	* testsuite/27_io/basic_stringbuf/seekpos/char/3.cc: Tweak
 	line spacing.
 
diff --git a/libstdc++-v3/include/bits/fstream.tcc b/libstdc++-v3/include/bits/fstream.tcc
index b791579..e84eee0 100644
--- a/libstdc++-v3/include/bits/fstream.tcc
+++ b/libstdc++-v3/include/bits/fstream.tcc
@@ -268,54 +268,39 @@ namespace std
 
       if (__testin)
 	{
-	  const bool __testpb = this->_M_in_beg < this->_M_in_cur;
-	  char_type __c = traits_type::to_char_type(__i);
+	  // Remember whether the pback buffer is active, otherwise below
+	  // we may try to store in it a second char (libstdc++/9761).
+	  const bool __testpb = this->_M_pback_init;	   
 	  const bool __testeof = traits_type::eq_int_type(__i, __ret);
-
-	  if (__testpb)
+	  
+	  int_type __tmp;
+	  if (this->_M_in_beg < this->_M_in_cur)
 	    {
-	      const bool __testout = this->_M_mode & ios_base::out;
-	      const bool __testeq = traits_type::eq(__c, this->_M_in_cur[-1]);
-
-	      --this->_M_in_cur;
-	      if (__testout)
-		--this->_M_out_cur;
-	      // Try to put back __c into input sequence in one of three ways.
-	      // Order these tests done in is unspecified by the standard.
-	      if (!__testeof && __testeq)
-		__ret = __i;
-	      else if (__testeof)
-		__ret = traits_type::not_eof(__i);
-	      else
-		{
-		  _M_create_pback();
-		  *this->_M_in_cur = __c; 
-		  __ret = __i;
-		}
+	      _M_move_in_cur(-1);
+	      __tmp = traits_type::to_int_type(*this->_M_in_cur);
+	    }
+	  // At the beginning of the buffer, need to make a
+	  // putback position available.
+	  // But the seek may fail (f.i., at the beginning of
+	  // a file, see libstdc++/9439) and in that case
+	  // we return traits_type::eof().
+	  else if (this->seekoff(-1, ios_base::cur) < 0
+		   || traits_type::eq_int_type(__tmp = this->underflow(),
+					       traits_type::eof()))
+	    return __ret;
+
+	  // Try to put back __i into input sequence in one of three ways.
+	  // Order these tests done in is unspecified by the standard.
+	  if (!__testeof && traits_type::eq_int_type(__i, __tmp))
+	    __ret = __i;
+	  else if (__testeof)
+	    __ret = traits_type::not_eof(__i);
+	  else if (!__testpb)
+	    {
+	      _M_create_pback();
+	      *this->_M_in_cur = traits_type::to_char_type(__i); 
+	      __ret = __i;
 	    }
-	  else
-	    {	 
- 	      // At the beginning of the buffer, need to make a
-	      // putback position available.
-	      // But the seek may fail (f.i., at the beginning of
-	      // a file, see libstdc++/9439) and in that case
-	      // we return traits_type::eof()
-	      if (this->seekoff(-1, ios_base::cur) >= 0)
-		{
-		  this->underflow();
-		  if (!__testeof)
-		    {
-		      if (!traits_type::eq(__c, *this->_M_in_cur))
-			{
-			  _M_create_pback();
-			  *this->_M_in_cur = __c;
-			}
-		      __ret = __i;
-		    }
-		  else
-		    __ret = traits_type::not_eof(__i);
-		}
- 	    }
 	}
       _M_last_overflowed = false;	
       return __ret;
diff --git a/libstdc++-v3/testsuite/27_io/basic_filebuf/pbackfail/char/9761.cc b/libstdc++-v3/testsuite/27_io/basic_filebuf/pbackfail/char/9761.cc
new file mode 100644
index 0000000..07e1dda
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/basic_filebuf/pbackfail/char/9761.cc
@@ -0,0 +1,55 @@
+// 2003-06-02 Paolo Carlini <pcarlini@unitus.it>
+
+// Copyright (C) 2003 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+// USA.
+
+// 27.8.1.4 Overridden virtual functions
+
+#include <fstream>
+#include <testsuite_hooks.h>
+
+const char name_01[] = "filebuf_virtuals-1.txt"; // file with data in it
+
+// libstdc++/9761
+void test01()
+{
+  using namespace std;
+  bool test = true;
+
+  filebuf fbuf;
+  filebuf::int_type r1, r2;
+
+  fbuf.open(name_01, ios_base::in);
+  
+  fbuf.sbumpc();
+  fbuf.sbumpc();
+	
+  r1 = fbuf.sputbackc('a');
+  r2 = fbuf.sputbackc('b');
+
+  fbuf.close();
+
+  VERIFY( r1 != filebuf::traits_type::eof() );
+  VERIFY( r2 == filebuf::traits_type::eof() );
+}
+
+main() 
+{
+  test01();
+  return 0;
+}