Q102158: FIX: ifstream Object Loses Character in Text Mode

Article: Q102158
Product(s): Microsoft C Compiler
Version(s): 1.0,1.5,2.0,4.0,4.1,4.2
Operating System(s): 
Keyword(s): kbcode kbCompiler kbCPPonly kbVC100 kbVC150 kbVC200 kbVC400 kbVC410 kbVC420 kbVC500fix
Last Modified: 29-NOV-2001

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The information in this article applies to:

- Microsoft C/C++ for MS-DOS 
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5 
- Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 4.0, 4.1 
- Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
- Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
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SYMPTOMS
========

When an application reads characters into an ifstream object opened in text
mode, data may be lost and not placed into the buffer. The code does not provide
any warning or other indication of this data loss.

STATUS
======

Microsoft has confirmed this to be a problem in the products listed at the
beginning of this article. This problem was fixed in Visual C++ 5.0.

MORE INFORMATION
================

The following code example demonstrates this problem by filling a buffer with
the character sequence "01234567890..." and using an ifstream object to copy the
data to another buffer. The transferred sequence reads as "013456..." Only the
character "2" is missing from the sequence. The remainder of the sequence
transfers correctly.

Sample Code
-----------

  /*
   * Compiler options needed:  -GX for 5.0 only
   */ 

  #include <iostream.h>
  #include <fstream.h>

  // To resolve the problem using Visual C++ 5.0, use the
  // following three statements instead of the preceding two:
  // 
  // #include <iostream>
  // #include <fstream>
  // using namespace std;

  void main(void)
  {
     ofstream os("test.tmp");
     for (int i = 0; i < 512; i++)
     {
        os.put((char)('0' + i % 10));
     }
     os.put('\n');
     os.close();

     streampos pos;
     ifstream is("test.tmp");
  // To resolve this error using Visual C++ 4.x and earlier, use the
  // following line to open the ifstream instead of the line above.
  // ifstream is("test.tmp", ios::binary);
     for (int k = 0; k < 10; k++)
     {
        pos = is.tellg();
        cout << (char)is.get();
     }
  }


Additional query words: kbVC400bug 8.00 8.00c 9.00

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Keywords          : kbcode kbCompiler kbCPPonly kbVC100 kbVC150 kbVC200 kbVC400 kbVC410 kbVC420 kbVC500fix 
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbZNotKeyword8 kbvc150 kbvc100 kbZNotKeyword3 kbVC410 kbVC420 kbVC200 kbVC32bitSearch kbVC16bitSearch
Version           : :1.0,1.5,2.0,4.0,4.1,4.2
Issue type        : kbbug
Solution Type     : kbfix

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