BUG: Listing Sort Function Removes Elements

ID: Q240014

The information in this article applies to:

The Standard C++ Library, included with:
- Microsoft Visual C++, 32-bit Editions, version 6.0

SYMPTOMS

If a list has over 32K elements, list::sort removes the elements.
Please refer to the Sample Program in the MORE INFORMATION section for details.

RESOLUTION

The bug is in the header file <list>.

In the sort() function:


   if (_I == _MAXN)
	//_A[_I].merge(_X); /* remove this line and add the line below*/ 
	_A[_I - 1].merge(_X);

In the sort(_Pr3 _Pr) function :


   if (_I == _MAXN)
	//_A[_I].merge(_X, _Pr); /* remove this line and add the line below*/ 
	_A[_I - 1].merge(_X, _Pr);<BR/>

If you are sorting through a list larger than 32K, increasing _MAXN from 15 to 25 would improve the performance.

NOTE: Since the resolution involves modifying a system header file, extreme care should be taken to make sure nothing else is changed in the header file. Microsoft is not responsible for any problems resulting due to unwanted changes to the system header files.

STATUS

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

MORE INFORMATION

Steps to Reproduce Behavior

The following sample program demonstrates the bug.


   //test.cpp
   //Compiler options : /GX
   #include <list>
   #include <algorithm>
   #include <iostream>

   void main()
   {
     std::list<int> mylist;

     int i;
     int last = 32768;

     for (i = 0; i < last; i++)
    mylist.push_back(i);


     std::cout << "Size before sort: " << mylist.size() << "\n";
     mylist.sort();
     std::cout << "Size after sort: " << mylist.size() << "\n";
   }

   Actual Results:
   Size before sort: 32768
   Size after sort: 0

   Expected Results:
   Size before sort: 32768
   Size after sort: 32768

Additional query words: STL

Keywords : kbLangCPP kbSTL kbVC600 kbVC600bug
Version : winnt:6.0
Platform : winnt
Issue type : kbbug