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

 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
 	* include/bits/fstream.tcc (overflow): don't write EOF to file.

libstdc++-v3/acinclude.m4

@@ -591,34 +591,6 @@ AC_DEFUN(GLIBCPP_CHECK_STDLIB_DECL_AND_LINKAGE_3, [
 ])
 
 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.
 dnl Check to see if the (math function) argument passed is
@@ -753,26 +725,6 @@ AC_DEFUN(GLIBCPP_CHECK_STDLIB_SUPPORT, [
 ])
 
 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:
 dnl 1) make sure the name is declared when using the c++ compiler

libstdc++-v3/aclocal.m4

-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
@@ -603,34 +603,6 @@ AC_DEFUN(GLIBCPP_CHECK_STDLIB_DECL_AND_LINKAGE_3, [
 ])
 
 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.
 dnl Check to see if the (math function) argument passed is
@@ -765,26 +737,6 @@ AC_DEFUN(GLIBCPP_CHECK_STDLIB_SUPPORT, [
 ])
 
 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="$ac_save_CXXFLAGS"
-])
-
-dnl
 dnl Check to see what the underlying c library or math library is like.
 dnl These checks need to do two things:
 dnl 1) make sure the name is declared when using the c++ compiler
@@ -2313,7 +2265,7 @@ AC_MSG_RESULT($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

 // 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)
-  { return fread(__s, 1, __n, _M_cfile); }
-  
+  __basic_file<char>::xsgetn(char* __s, streamsize __n, bool __stdio)
+  {
+    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)
-  { return fwrite(__s, 1, __n, _M_cfile); }
+  __basic_file<char>::xsputn(const char* __s, streamsize __n, bool __stdio)
+  {
+    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))
-      return ftell(_M_cfile); 
+    if (!__stdio)
+      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))
-      return ftell(_M_cfile);
+    if (!__stdio)
+      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 || isatty (0)) ? 1 : static_cast<size_t>(BUFSIZ);
-#else
-    size_t __in_size = 1;
-#endif
+    size_t __in_size = __sync ? 1 : static_cast<size_t>(BUFSIZ);
 
     // 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;
 }