FIX: Access violation when you use the Realloc function in a small memory block in Visual C++ 6.0 (225099)

RESOLUTION

Here are three ways to work around this problem:

1. In the following code block in the Realloc.c file:

   //  if the new size is not over __sbh_threshold, attempt
   //  to reallocate within the small-block heap
   if (newsize <= __sbh_threshold)
   {
      if (__sbh_resize_block(pHeader, pBlock, newsize))
         pvReturn = pBlock;
      else if ((pvReturn = __sbh_alloc_block(newsize)) != NULL)
      {
         oldsize = ((PENTRY)((char *)pBlock -
                            sizeof(int)))->sizeFront - 1;
         memcpy(pvReturn, pBlock, __min(oldsize, newsize));
         __sbh_free_block(pHeader, pBlock);
      }
   }
   						

   Replace this line of code:

   __sbh_free_block(pHeader, pBlock);

   with this:

   pHeader = __sbh_find_block(pBlock);
   __sbh_free_block(pHeader, pBlock);

   And rebuild CRT. NOTE: If you are rebuilding the DLL version of CRT, then the new DLL name should not start with "msvc".
2. Implement your own Realloc() function to avoid using the CRT implementation.
3. Use the _set_sbh_threshold(0) function to avoid the use of the small block heap. Both Windows NT 4.0 SP4 and Windows 2000 have an efficient OS-level heap implementation. You may encounter performance problems on Windows 95 and Windows 98 because its operating system heap implementation is not as efficient as the one on Windows NT.

A supported fix for the Visual C++ 6.0 static libraries that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

The English version of this fix should have the following file attributes or later:

Name	Size	Date	Time	Version	Platform
Libc.lib	843,586	12/20/1999	6:41 PM	none	x86
Libcd.lib	2,538,44	12/20/1999	6:52 PM	none	x86
Libcd.pdb	94,208	12/20/1999	6:52 PM	none	x86
Libci.lib	165,800	12/20/1999	6:41 PM	none	x86
Libcid.lib	397,510	12/20/1999	6:53 PM	none	x86
Libcid.pdb	77,824	12/20/1999	6:53 PM	none	x86
Libcimt.lib	178,144	12/20/1999	6:45 PM	none	x86
Libcimtd.lib	604,376	12/20/1999	6:56 PM	none	x86
Libcimtd.pdb	86,016	12/20/1999	6:56 PM	none	x86
Libcmt.lib	893,390	12/20/1999	6:44 PM	none	x86
Libcmtd.lib	3,151,58	12/20/1999	6:56 PM	none	x86
Libcmtd.pdb	94,208	12/20/1999	6:56 PM	none	x86
Libcp.lib	721,584	12/20/1999	6:41 PM	none	x86
Libcpd.lib	1,639,90	12/20/1999	6:53 PM	none	x86
Libcpd.pdb	167,936	12/20/1999	6:53 PM	none	x86
Libcpmt.lib	735,302	12/20/1999	6:44 PM	none	x86
Libcpmtd.lib	1,647,60	12/20/1999	6:56 PM	none	x86
Libcpmtd.pdb	167,936	12/20/1999	6:56 PM	none	x86

in the following self-extracting file:

Name	Size	Date	Time	Platform
VC225099.EXE	3,345,777	1/17/2000	1:30 PM	x86

NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, a fee may be charged. This fee is refundable if it is determined that you only require the fix you requested. However, this fee is non-refundable if you request additional technical support, if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support.

//main.cpp

#include "stdio.h"
#include "stdlib.h"

int main()
{
	char* pData;

	for( int i=0; i< 70000; i++ )
	{
            pData = (char*)malloc( 32 );
            pData = (char*)realloc( pData, 290 );  //access violation in small-block allocator 
	}	

	return(0);
} //end main