re PR libstdc++/7744 (streambuf::in_avail() always returns 0 (zero) for cin input stream)

2003-03-09  Paolo Carlini  <pcarlini@unitus.it>
	    Nathan Myers  <ncm@cantrip.org>

	PR libstdc++/7744
	* config/io/basic_file_stdio.h (__basic_file<>::xsgetn, xsputn,
	seekoff, seekpos): Add a boolean parameter __stdio.
	* config/io/basic_file_stdio.cc (__basic_file<>::xsgetn, xsputn,
	seekoff, seekpos): If __stdio == true, use fread (fwrite, fseek/ftell,
	fseek/ftell, respectively), otherwise read (write, lseek, lseek,
	respectively).
	* include/bits/fstream.tcc (basic_filebuf<>::_M_convert_to_external,
	_M_really_overflow, seekoff): Use the boolean parameter in the calls.
	* include/std/std_fstream.h (sync): Likewise.
	* src/fstream.cc (basic_filebuf<>::_M_underflow_common): Likewise.
	* src/ios.cc (ios_base::Init::_S_ios_create(bool)): Revert libstdc++/8399
	commit involving isatty(0).
	* acinclude.m4 (GLIBCPP_CHECK_UNISTD_DECL_AND_LINKAGE_1): Remove.
        (GLIBCPP_CHECK_UNISTD_SUPPORT): Remove
  	* configure.in: Remove call.
	* aclocal.m4: Regenerate.
       	* config.h.in: Regenerate.
        * configure: Regenerate.
	* testsuite/27_io/narrow_stream_objects.cc (test11): Add.

Co-Authored-By: Nathan Myers <ncm@cantrip.org>

From-SVN: r64051

libstdc++-v3/ChangeLog

@@ -1,3 +1,27 @@
+2003-03-09  Paolo Carlini  <pcarlini@unitus.it>
+            Nathan Myers  <ncm@cantrip.org>
+
+	PR libstdc++/7744
+	* config/io/basic_file_stdio.h (__basic_file<>::xsgetn, xsputn,
+	seekoff, seekpos): Add a boolean parameter __stdio.
+	* config/io/basic_file_stdio.cc (__basic_file<>::xsgetn, xsputn,
+	seekoff, seekpos): If __stdio == true, use fread (fwrite, fseek/ftell,
+	fseek/ftell, respectively), otherwise read (write, lseek, lseek,
+	respectively).
+	* include/bits/fstream.tcc (basic_filebuf<>::_M_convert_to_external,
+	_M_really_overflow, seekoff): Use the boolean parameter in the calls.
+	* include/std/std_fstream.h (sync): Likewise.
+	* src/fstream.cc (basic_filebuf<>::_M_underflow_common): Likewise.
+	* src/ios.cc (ios_base::Init::_S_ios_create(bool)): Revert libstdc++/8399
+	commit involving isatty(0).
+	* acinclude.m4 (GLIBCPP_CHECK_UNISTD_DECL_AND_LINKAGE_1): Remove.
+	(GLIBCPP_CHECK_UNISTD_SUPPORT): Remove
+	* configure.in: Remove call.
+	* aclocal.m4: Regenerate.
+	* config.h.in: Regenerate.
+	* configure: Regenerate.
+	* testsuite/27_io/narrow_stream_objects.cc (test11): Add.
+
 2003-03-09  Paolo Carlini  <pcarlini@unitus.it>
 
 	PR libstdc++/9988

libstdc++-v3/acinclude.m4

@@ -590,34 +590,6 @@ AC_DEFUN(GLIBCPP_CHECK_STDLIB_DECL_AND_LINKAGE_3, [
   fi
 ])
 
-dnl
-dnl Check to see if the (unistd function) argument passed is
-dnl 1) declared when using the c++ compiler
-dnl 2) has "C" linkage
-dnl
-dnl argument 1 is name of function to check
-dnl
-dnl ASSUMES argument is a function with ONE parameter
-dnl
-dnl GLIBCPP_CHECK_UNISTD_DECL_AND_LINKAGE_1
-AC_DEFUN(GLIBCPP_CHECK_UNISTD_DECL_AND_LINKAGE_1, [
-  AC_MSG_CHECKING([for $1 declaration])
-  if test x${glibcpp_cv_func_$1_use+set} != xset; then
-    AC_CACHE_VAL(glibcpp_cv_func_$1_use, [
-      AC_LANG_SAVE
-      AC_LANG_CPLUSPLUS
-      AC_TRY_COMPILE([#include <unistd.h>],
-                     [ $1(0);],
-                     [glibcpp_cv_func_$1_use=yes], [glibcpp_cv_func_$1_use=no])
-      AC_LANG_RESTORE
-    ])
-  fi
-  AC_MSG_RESULT($glibcpp_cv_func_$1_use)
-  if test x$glibcpp_cv_func_$1_use = x"yes"; then
-    AC_CHECK_FUNCS($1)
-  fi
-])
-
 dnl
 dnl Because the builtins are picky picky picky about the arguments they take,
 dnl do an explict linkage tests here.
@@ -752,26 +724,6 @@ AC_DEFUN(GLIBCPP_CHECK_STDLIB_SUPPORT, [
   CXXFLAGS="$ac_save_CXXFLAGS"
 ])
 
-dnl
-dnl Check to see what the underlying c library is like
-dnl These checks need to do two things:
-dnl 1) make sure the name is declared when using the c++ compiler
-dnl 2) make sure the name has "C" linkage
-dnl This might seem like overkill but experience has shown that it's not...
-dnl
-dnl Define HAVE_ISATTY if "isatty" is declared and links
-dnl
-dnl GLIBCPP_CHECK_UNISTD_SUPPORT
-AC_DEFUN(GLIBCPP_CHECK_UNISTD_SUPPORT, [
-  ac_test_CXXFLAGS="${CXXFLAGS+set}"
-  ac_save_CXXFLAGS="$CXXFLAGS"
-  CXXFLAGS='-fno-builtins -D_GNU_SOURCE'
-
-  GLIBCPP_CHECK_UNISTD_DECL_AND_LINKAGE_1(isatty)
-
-  CXXFLAGS="$ac_save_CXXFLAGS"
-])
-
 dnl
 dnl Check to see what the underlying c library or math library is like.
 dnl These checks need to do two things:

libstdc++-v3/aclocal.m4

@@ -1,4 +1,4 @@
-dnl aclocal.m4 generated automatically by aclocal 1.4-p5
+dnl aclocal.m4 generated automatically by aclocal 1.4-p6
 
 dnl Copyright (C) 1994, 1995-8, 1999, 2001 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
@@ -602,34 +602,6 @@ AC_DEFUN(GLIBCPP_CHECK_STDLIB_DECL_AND_LINKAGE_3, [
   fi
 ])
 
-dnl
-dnl Check to see if the (unistd function) argument passed is
-dnl 1) declared when using the c++ compiler
-dnl 2) has "C" linkage
-dnl
-dnl argument 1 is name of function to check
-dnl
-dnl ASSUMES argument is a function with ONE parameter
-dnl
-dnl GLIBCPP_CHECK_UNISTD_DECL_AND_LINKAGE_1
-AC_DEFUN(GLIBCPP_CHECK_UNISTD_DECL_AND_LINKAGE_1, [
-  AC_MSG_CHECKING([for $1 declaration])
-  if test x${glibcpp_cv_func_$1_use+set} != xset; then
-    AC_CACHE_VAL(glibcpp_cv_func_$1_use, [
-      AC_LANG_SAVE
-      AC_LANG_CPLUSPLUS
-      AC_TRY_COMPILE([#include <unistd.h>],
-                     [ $1(0);],
-                     [glibcpp_cv_func_$1_use=yes], [glibcpp_cv_func_$1_use=no])
-      AC_LANG_RESTORE
-    ])
-  fi
-  AC_MSG_RESULT($glibcpp_cv_func_$1_use)
-  if test x$glibcpp_cv_func_$1_use = x"yes"; then
-    AC_CHECK_FUNCS($1)
-  fi
-])
-
 dnl
 dnl Because the builtins are picky picky picky about the arguments they take,
 dnl do an explict linkage tests here.
@@ -764,26 +736,6 @@ AC_DEFUN(GLIBCPP_CHECK_STDLIB_SUPPORT, [
   CXXFLAGS="$ac_save_CXXFLAGS"
 ])
 
-dnl
-dnl Check to see what the underlying c library is like
-dnl These checks need to do two things:
-dnl 1) make sure the name is declared when using the c++ compiler
-dnl 2) make sure the name has "C" linkage
-dnl This might seem like overkill but experience has shown that it's not...
-dnl
-dnl Define HAVE_ISATTY if "isatty" is declared and links
-dnl
-dnl GLIBCPP_CHECK_UNISTD_SUPPORT
-AC_DEFUN(GLIBCPP_CHECK_UNISTD_SUPPORT, [
-  ac_test_CXXFLAGS="${CXXFLAGS+set}"
-  ac_save_CXXFLAGS="$CXXFLAGS"
-  CXXFLAGS='-fno-builtins -D_GNU_SOURCE'
-
-  GLIBCPP_CHECK_UNISTD_DECL_AND_LINKAGE_1(isatty)
-
-  CXXFLAGS="$ac_save_CXXFLAGS"
-])
-
 dnl
 dnl Check to see what the underlying c library or math library is like.
 dnl These checks need to do two things:
@@ -2313,7 +2265,7 @@ AC_MSG_RESULT($enable_symvers)
 ])
 
 
-# isc-posix.m4 serial 1 (gettext-0.10.40)
+# isc-posix.m4 serial 2 (gettext-0.11.2)
 dnl Copyright (C) 1995-2002 Free Software Foundation, Inc.
 dnl This file is free software, distributed under the terms of the GNU
 dnl General Public License.  As a special exception to the GNU General
@@ -2321,6 +2273,8 @@ dnl Public License, this file may be distributed as part of a program
 dnl that contains a configuration script generated by Autoconf, under
 dnl the same distribution terms as the rest of that program.
 
+# This file is not needed with autoconf-2.53 and newer.  Remove it in 2005.
+
 # This test replaces the one in autoconf.
 # Currently this macro should have the same name as the autoconf macro
 # because gettext's gettext.m4 (distributed in the automake package)
@@ -2381,7 +2335,8 @@ dnl Usage:
 dnl AM_INIT_AUTOMAKE(package,version, [no-define])
 
 AC_DEFUN([AM_INIT_AUTOMAKE],
-[AC_REQUIRE([AC_PROG_INSTALL])
+[AC_REQUIRE([AM_SET_CURRENT_AUTOMAKE_VERSION])dnl
+AC_REQUIRE([AC_PROG_INSTALL])
 PACKAGE=[$1]
 AC_SUBST(PACKAGE)
 VERSION=[$2]
@@ -2397,13 +2352,42 @@ AC_REQUIRE([AM_SANITY_CHECK])
 AC_REQUIRE([AC_ARG_PROGRAM])
 dnl FIXME This is truly gross.
 missing_dir=`cd $ac_aux_dir && pwd`
-AM_MISSING_PROG(ACLOCAL, aclocal, $missing_dir)
+AM_MISSING_PROG(ACLOCAL, aclocal-${am__api_version}, $missing_dir)
 AM_MISSING_PROG(AUTOCONF, autoconf, $missing_dir)
-AM_MISSING_PROG(AUTOMAKE, automake, $missing_dir)
+AM_MISSING_PROG(AUTOMAKE, automake-${am__api_version}, $missing_dir)
 AM_MISSING_PROG(AUTOHEADER, autoheader, $missing_dir)
 AM_MISSING_PROG(MAKEINFO, makeinfo, $missing_dir)
 AC_REQUIRE([AC_PROG_MAKE_SET])])
 
+# Copyright 2002  Free Software Foundation, Inc.
+
+# 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 2, 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+
+# AM_AUTOMAKE_VERSION(VERSION)
+# ----------------------------
+# Automake X.Y traces this macro to ensure aclocal.m4 has been
+# generated from the m4 files accompanying Automake X.Y.
+AC_DEFUN([AM_AUTOMAKE_VERSION],[am__api_version="1.4"])
+
+# AM_SET_CURRENT_AUTOMAKE_VERSION
+# -------------------------------
+# Call AM_AUTOMAKE_VERSION so it can be traced.
+# This function is AC_REQUIREd by AC_INIT_AUTOMAKE.
+AC_DEFUN([AM_SET_CURRENT_AUTOMAKE_VERSION],
+	 [AM_AUTOMAKE_VERSION([1.4-p6])])
+
 #
 # Check to make sure that the build environment is sane.
 #

libstdc++-v3/config.h.in

@@ -461,9 +461,6 @@
 /* Define if you have the iconv_open function.  */
 #undef HAVE_ICONV_OPEN
 
-/* Define if you have the isatty function.  */
-#undef HAVE_ISATTY
-
 /* Define if you have the isinf function.  */
 #undef HAVE_ISINF
 

libstdc++-v3/config/io/basic_file_stdio.cc

@@ -1,6 +1,6 @@
 // Wrapper of C-language FILE struct -*- C++ -*-
 
-// Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.
+// Copyright (C) 2000, 2001, 2002, 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
@@ -33,6 +33,7 @@
 
 #include <bits/basic_file.h>
 #include <fcntl.h>
+#include <errno.h>
 
 namespace std 
 {
@@ -191,33 +192,69 @@ namespace std
     return __retval;
   }
  
+  // In the next four functions we want to use stdio functions only
+  // when synced with stdio (_M_buf_size == 1): I/O primitives do not
+  // block until the asked number of bytes are available.
   streamsize 
-  __basic_file<char>::xsgetn(char* __s, streamsize __n)
+  __basic_file<char>::xsgetn(char* __s, streamsize __n, bool __stdio)
-  { return fread(__s, 1, __n, _M_cfile); }
+  {
-  
+    if (__stdio)
+      return fread(__s, 1, __n, _M_cfile);
+    else
+      {
+	streamsize __ret;
+        do
+	  __ret = read(this->fd(), __s, __n);
+	while (__ret == -1L && errno == EINTR);
+	return __ret;
+      }
+  }
+    
   streamsize 
-  __basic_file<char>::xsputn(const char* __s, streamsize __n)
+  __basic_file<char>::xsputn(const char* __s, streamsize __n, bool __stdio)
-  { return fwrite(__s, 1, __n, _M_cfile); }
+  {
+    if (__stdio)
+      return fwrite(__s, 1, __n, _M_cfile);
+    else
+      {
+	streamsize __ret;
+        do
+	  __ret = write(this->fd(), __s, __n);
+	while (__ret == -1L && errno == EINTR);
+	return __ret;
+      }
+  }
   
   streamoff
   __basic_file<char>::seekoff(streamoff __off, ios_base::seekdir __way, 
-			      ios_base::openmode /*__mode*/)
+			      bool __stdio, ios_base::openmode /*__mode*/)
   { 
-    if (!fseek(_M_cfile, __off, __way))
+    if (!__stdio)
-      return ftell(_M_cfile); 
+      return lseek(this->fd(), __off, __way);
     else
-      // Fseek failed.
+      {
-      return -1L;
+	if (!fseek(_M_cfile, __off, __way))
+	  return ftell(_M_cfile); 
+	else
+	  // Fseek failed.
+	  return -1L;
+      }
   }
 
   streamoff
-  __basic_file<char>::seekpos(streamoff __pos, ios_base::openmode /*__mode*/)
+  __basic_file<char>::seekpos(streamoff __pos, bool __stdio,
+			      ios_base::openmode /*__mode*/)
   { 
-    if (!fseek(_M_cfile, __pos, ios_base::beg))
+    if (!__stdio)
-      return ftell(_M_cfile);
+      return lseek(this->fd(), __pos, ios_base::beg);
     else
-      // Fseek failed.
+      {
-      return -1L;
+	if (!fseek(_M_cfile, __pos, ios_base::beg))
+	  return ftell(_M_cfile);
+	else
+	  // Fseek failed.
+	  return -1L;
+      }
   }
   
   int 

libstdc++-v3/config/io/basic_file_stdio.h

@@ -93,17 +93,17 @@ namespace std
       ~__basic_file();
 
       streamsize 
-      xsputn(const char* __s, streamsize __n);
+      xsputn(const char* __s, streamsize __n, bool __stdio);
 
       streamsize 
-      xsgetn(char* __s, streamsize __n);
+      xsgetn(char* __s, streamsize __n, bool __stdio);
 
       streamoff
-      seekoff(streamoff __off, ios_base::seekdir __way,
+      seekoff(streamoff __off, ios_base::seekdir __way, bool __stdio,
 	      ios_base::openmode __mode = ios_base::in | ios_base::out);
 
       streamoff
-      seekpos(streamoff __pos, 
+      seekpos(streamoff __pos, bool __stdio,
 	      ios_base::openmode __mode = ios_base::in | ios_base::out);
 
       int 

libstdc++-v3/configure.in

@@ -411,7 +411,6 @@ else
   GLIBCPP_CHECK_COMPLEX_MATH_SUPPORT
   GLIBCPP_CHECK_WCHAR_T_SUPPORT
   GLIBCPP_CHECK_STDLIB_SUPPORT
-  GLIBCPP_CHECK_UNISTD_SUPPORT
   AC_LC_MESSAGES
 
   AC_TRY_COMPILE([

libstdc++-v3/include/bits/fstream.tcc

@@ -102,7 +102,7 @@ namespace std
 	      // using underflow.
  	      if (__mode & ios_base::in && _M_buf_allocated)
  		this->underflow();
-	      
+
 	      if ((__mode & ios_base::ate)
 		  && this->seekoff(0, ios_base::end, __mode) < 0)
 		{
@@ -276,10 +276,13 @@ namespace std
     {
       const locale __loc = this->getloc();
       const __codecvt_type& __cvt = use_facet<__codecvt_type>(__loc);
-      
+      // Sync with stdio.
+      bool __sync = this->_M_buf_size == 1;
+
       if (__cvt.always_noconv() && __ilen)
 	{
-	  __elen += _M_file.xsputn(reinterpret_cast<char*>(__ibuf), __ilen);
+	  __elen +=
+	    _M_file.xsputn(reinterpret_cast<char*>(__ibuf), __ilen, __sync);
 	  __plen += __ilen;
 	}
       else
@@ -309,7 +312,7 @@ namespace std
 	  
 	  if (__blen)
 	    {
-	      __elen += _M_file.xsputn(__buf, __blen);
+	      __elen += _M_file.xsputn(__buf, __blen, __sync);
 	      __plen += __blen;
 	    }
 
@@ -331,7 +334,7 @@ namespace std
 		}
 	      if (__rlen)
 		{
-		  __elen += _M_file.xsputn(__buf, __rlen);
+		  __elen += _M_file.xsputn(__buf, __rlen, __sync);
 		  __plen += __rlen;
 		}
 	    }
@@ -346,6 +349,8 @@ namespace std
       int_type __ret = traits_type::eof();
       bool __testput = this->_M_out_cur && this->_M_out_beg < this->_M_out_lim;
       bool __testunbuffered = _M_file.is_open() && !this->_M_buf_size_opt;
+      // Sync with stdio.
+      bool __sync = this->_M_buf_size == 1;
 
       if (__testput || __testunbuffered)
 	{
@@ -359,7 +364,7 @@ namespace std
 	  if (_M_filepos && _M_filepos != this->_M_out_beg)
 	    {
 	      off_type __off = this->_M_out_beg - _M_filepos;
-	      _M_file.seekoff(__off, ios_base::cur);
+	      _M_file.seekoff(__off, ios_base::cur, __sync);
 	    }
 
 	  // Convert internal buffer to external representation, output.
@@ -434,7 +439,9 @@ namespace std
       pos_type __ret =  pos_type(off_type(-1)); 
       bool __testin = (ios_base::in & this->_M_mode & __mode) != 0;
       bool __testout = (ios_base::out & this->_M_mode & __mode) != 0;
-
+      // Sync with stdio.
+      bool __sync = this->_M_buf_size == 1;
+      
       // Should probably do has_facet checks here.
       int __width = use_facet<__codecvt_type>(this->_M_buf_locale).encoding();
       if (__width < 0)
@@ -468,7 +475,7 @@ namespace std
 		__computed_off += this->_M_in_cur - _M_filepos;
 
 	      // Return pos_type(off_type(-1)) in case of failure.
-	      __ret = _M_file.seekoff(__computed_off, __way, __mode);
+	      __ret = _M_file.seekoff(__computed_off, __way, __sync, __mode);
 	      _M_set_indeterminate();
 	    }
 	  // NB: Need to do this in case _M_file in indeterminate
@@ -476,7 +483,8 @@ namespace std
 	  else
 	    {
 	      pos_type __tmp =
-		_M_file.seekoff(__off, ios_base::cur, __mode);
+		_M_file.seekoff(__off, ios_base::cur,
+				__sync, __mode);
 	      if (__tmp >= 0)
 		{
 		  // Seek successful.

libstdc++-v3/include/std/std_fstream.h

@@ -314,6 +314,8 @@ namespace std
 	int __ret = 0;
 	bool __testput = this->_M_out_cur
 	  && this->_M_out_beg < this->_M_out_lim;
+	// Sync with stdio.
+	bool __sync = this->_M_buf_size == 1;
 
 	// Make sure that the internal buffer resyncs its idea of
 	// the file position with the external file.
@@ -327,7 +329,7 @@ namespace std
 					 traits_type::eof()))
 	      __ret = -1;
 	    else if (__off)
-	      _M_file.seekoff(__off, ios_base::cur);
+	      _M_file.seekoff(__off, ios_base::cur, __sync);
 	  }
 	else
 	  _M_file.sync();

libstdc++-v3/src/fstream.cc

@@ -43,6 +43,8 @@ namespace std
       int_type __ret = traits_type::eof();
       bool __testin = _M_mode & ios_base::in;
       bool __testout = _M_mode & ios_base::out;
+      // Sync with stdio.
+      bool __sync = _M_buf_size == 1;
 
       if (__testin)
 	{
@@ -71,15 +73,16 @@ namespace std
 		_M_really_overflow();
 	      else if (_M_in_cur != _M_filepos)
 		_M_file.seekoff(_M_in_cur - _M_filepos,
-				ios_base::cur, ios_base::in);
+				ios_base::cur, __sync, ios_base::in);
 	    }
 
 	  if (__testinit || __testget)
 	    {
 	      streamsize __elen = 0;
 	      streamsize __ilen = 0;
+
 	      __elen = _M_file.xsgetn(reinterpret_cast<char*>(_M_in_beg), 
-				      _M_buf_size);
+				      _M_buf_size, __sync);
 	      __ilen = __elen;
 
 	      if (0 < __ilen)
@@ -90,7 +93,7 @@ namespace std
 		  __ret = traits_type::to_int_type(*_M_in_cur);
 		  if (__bump)
 		    _M_in_cur_move(1);
-		  else if (_M_buf_size == 1)
+		  else if (__sync)
 		    {
 		      // If we are synced with stdio, we have to unget the
 		      // character we just read so that the file pointer
@@ -123,6 +126,8 @@ namespace std
       int_type __ret = traits_type::eof();
       bool __testin = _M_mode & ios_base::in;
       bool __testout = _M_mode & ios_base::out;
+      // Sync with stdio.
+      bool __sync = _M_buf_size == 1;
 
       if (__testin)
 	{
@@ -151,7 +156,7 @@ namespace std
 		_M_really_overflow();
 	      else if (_M_in_cur != _M_filepos)
 		_M_file.seekoff(_M_in_cur - _M_filepos,
-				ios_base::cur, ios_base::in);
+				  ios_base::cur, __sync, ios_base::in);
 	    }
 
 	  if (__testinit || __testget)
@@ -164,13 +169,13 @@ namespace std
 	      if (__cvt.always_noconv())
 		{
 		  __elen = _M_file.xsgetn(reinterpret_cast<char*>(_M_in_beg), 
-					  _M_buf_size);
+					  _M_buf_size, __sync);
 		  __ilen = __elen;
 		}
 	      else
 		{
 		  char* __buf = static_cast<char*>(__builtin_alloca(_M_buf_size));
-		  __elen = _M_file.xsgetn(__buf, _M_buf_size);
+		  __elen = _M_file.xsgetn(__buf, _M_buf_size, __sync);
 
 		  const char* __eend;
 		  char_type* __iend;
@@ -183,7 +188,7 @@ namespace std
 		    {
 		      // Unwind.
 		      __ilen = 0;
-		      _M_file.seekoff(-__elen, ios_base::cur, ios_base::in);
+		      _M_file.seekoff(-__elen, ios_base::cur, __sync, ios_base::in);
 		    }
 		}
 
@@ -195,7 +200,7 @@ namespace std
 		  __ret = traits_type::to_int_type(*_M_in_cur);
 		  if (__bump)
 		    _M_in_cur_move(1);
-		  else if (_M_buf_size == 1)
+		  else if (__sync)
 		    {
 		      // If we are synced with stdio, we have to unget the
 		      // character we just read so that the file pointer

libstdc++-v3/src/ios.cc

@@ -38,9 +38,6 @@
 #include <fstream>
 #include <bits/atomicity.h>
 #include <ext/stdio_filebuf.h>
-#ifdef _GLIBCPP_HAVE_UNISTD_H
-#include <unistd.h>
-#endif
 
 namespace __gnu_cxx
 {
@@ -160,12 +157,7 @@ namespace std
   ios_base::Init::_S_ios_create(bool __sync)
   {
     size_t __out_size = __sync ? 0 : static_cast<size_t>(BUFSIZ);
-#ifdef _GLIBCPP_HAVE_ISATTY
+    size_t __in_size = __sync ? 1 : static_cast<size_t>(BUFSIZ);
-    size_t __in_size =
-      (__sync || isatty (0)) ? 1 : static_cast<size_t>(BUFSIZ);
-#else
-    size_t __in_size = 1;
-#endif
 
     // NB: The file globals.cc creates the four standard files
     // with NULL buffers. At this point, we swap out the dummy NULL

libstdc++-v3/testsuite/27_io/narrow_stream_objects.cc

@@ -204,6 +204,22 @@ test10()
   cout << "_M_gcount: "<< cin.gcount() << endl;
 }
 
+// libstdc++/7744
+void test11()
+{
+  std::ios::sync_with_stdio(false);
+
+  std::cout
+    << "\n:: f2() ::\n"
+    << "Type in the characters 'abc' and press <ENTER>: ";
+  std::cin.peek();
+ 
+  std::cout
+    << "The number of unread characters should be 4 (a, b, c, \\n): "
+    << std::cin.rdbuf()->in_avail()
+    << '\n';
+}
+
 int 
 main()
 {
@@ -218,5 +234,6 @@ main()
   // test08();
   // test09();
   // test10();
+  // test11();
   return 0;
 }