Q119393: BUG: Invalid Extraction from istrstream Does Not Set failbit

Article: Q119393
Product(s): Microsoft C Compiler
Version(s): 1.0,1.5,1.51,1.52,2.0,4.0,4.1,4.2,5.0,6.0
Operating System(s): 
Keyword(s): kbLangCPP kbVC kbVC100bug kbVC150bug kbVC151bug kbVC152bug kbVC200bug kbVC400bug kbVC41
Last Modified: 11-FEB-2002

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft C/C++ for MS-DOS 
- Microsoft Visual C++, versions 1.0, 1.5, 1.51, 1.52, 2.0, 4.0, 4.1 
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 5.0, 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 5.0, 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
- Microsoft Visual C++.NET (2002) 
-------------------------------------------------------------------------------

SYMPTOMS
========

If you extract an integer of an invalid octal value from istrstream, 0 is
extracted and the ios::failbit is not set. In addition, the ios::fail() function
returns FALSE, incorrectly indicating that the istrstream is valid.


RESOLUTION
==========

Use the manipulators (dec, hex, oct, binary, text) explicitly to set the correct
conversion base for the characters represented by the stream.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

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

A scenario that produces an unexpected result, and which may also reflect this
problem, involves using the string "08" to initialize the buffer used by the
istrstream (or any string where the first character is 0 and one of the
following characters is greater than 7).

This string causes the istrstream extraction operator to load the int with 0
instead of the expected value. This is because when 0 is the leading character
in a number and it is not followed by an x or X, the number is treated as an
octal number. Therefore, only the characters 0 through 7 after the leading 0 are
valid.

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

  /* Compile options needed: none
  */ 

  #include <strstrea.h>

  void main()
  {
     char buffer[10] = "08";
     int i;
     istrstream* str;

     str = new istrstream( buffer, 10 );

     // The following extraction is made with the expectation that
     // the i will be set to 8. However, it will be set to 0.
     *str >> i;

     // To fix this, change the line to:
     // *str >> dec >> i;

     cout << "i = " << i << endl;
     cout << "str->fail()=" << str->fail() << endl;
     delete str;
  }

Additional query words: kbVC400bug 8.00 8.00c 9.00 9.10

======================================================================
Keywords          : kbLangCPP kbVC kbVC100bug kbVC150bug kbVC151bug kbVC152bug kbVC200bug kbVC400bug kbVC410bug kbVC420bug kbVC500bug kbVC600bug 
Technology        : kbVCsearch kbAudDeveloper kbZNotKeyword8 kbvc150 kbvc100 kbZNotKeyword3 kbVC410 kbVC420 kbVC500 kbVC600 kbVC151 kbVC200 kbVC32bitSearch kbVC152 kbVC400 kbVCNET kbVC500Search
Version           : :1.0,1.5,1.51,1.52,2.0,4.0,4.1,4.2,5.0,6.0
Issue type        : kbbug

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.