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Date: Fri, 20 Dec 2002 06:46:00 -0000
From: peturr02@ru.is
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Subject: libstdc++/9024: Input fails after call to basic_filebuf<>::pubsetbuf(0, 0)
X-SW-Source: 2002-12/txt/msg01091.txt.bz2
List-Id: <gcc-prs.sourceware.org>


>Number:         9024
>Category:       libstdc++
>Synopsis:       Input fails after call to basic_filebuf<>::pubsetbuf(0, 0)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Dec 20 06:46:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     peturr02@ru.is
>Release:        gcc-3.2.1
>Organization:
>Environment:
Redhat Linux 8.0 on i686; glibc-2.2.93
>Description:
It is not possible to use a basic_ifstream s for input if s.rdbuf()->pubsetbuf(0, 0) has been called.

The call pubsetbuf(0, 0) is described in:

Bjarne Stroustrup, The C++ Programing Language, 3rd edition,
Section 21.6.4, page 647:
"By default, setbuf(0, 0) means "unbuffered""

Nicolai M. Josuttis, The C++ Standard Library, page 664:
"...the use of [pubsetbuf] is only portable if it is called
before the first I/O operation is performed and it is called as pubsetbuf(0, 0)..."
>How-To-Repeat:
See attachment.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="setbuf.cc"
Content-Disposition: inline; filename="setbuf.cc"

//////////////////////////////////////////////////////////////////////
// setbuf.cc
//
// Test program for basic_filebuf<>::pubsetbuf
//
// Bjarne Stroustrup, The C++ Programing Language, 3rd edition,
// Section 21.6.4, page 647:
// "By default, setbuf(0, 0) means "unbuffered""
//
// Nicolai M. Josuttis, The C++ Standard Library, page 664:
// "...the use of [pubsetbuf] is only portable if it is called
// before the first I/O operation is performed and it is called as
// pubsetbuf(0, 0)..."
//////////////////////////////////////////////////////////////////////

#include <fstream>
#include <string>
#include <iterator>
#include <algorithm>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cassert>
using namespace std;

int main()
{
  string const str1 = "abcdefghijklmnopqrstuvwxyz";
  string str2;
  string str3;

  char name[] = "pubsetbuftestXXXXXX";
  mktemp(name);

  {
    ofstream stream1;
    if (!stream1.rdbuf()->pubsetbuf(0, 0))
      assert(false);
    stream1.open(name);
    copy(str1.begin(), str1.end(), ostreambuf_iterator<char>(stream1));
  }

  {
    ifstream stream2;
    stream2.open(name);
    copy(istreambuf_iterator<char>(stream2), istreambuf_iterator<char>(),
	 back_inserter(str2));
  }

  {
    ifstream stream3;
    if (!stream3.rdbuf()->pubsetbuf(0, 0))
      assert(false);
    stream3.open(name);
    copy(istreambuf_iterator<char>(stream3),
	 istreambuf_iterator<char>(),
	 back_inserter(str3));
  }

  remove(name);
  
  cout << "str1 = " << str1 << endl;
  cout << "str2 = " << str2 << endl;
  cout << "str3 = " << str3 << endl;

  assert(str1 == str2);
  assert(str1 == str3);
  
  return 0;
}