BUG: "Out of Memory" Error When Saving to an Existing File

RESOLUTION

• Override the CDocument::GetFile() function to return a CFile object rather than a CMirrorFile object. You won't get the protection feature of CMirrorFile which checks to see whether you can write the whole file to the disk first. This may not be a problem depending upon what the application does. See the code the CDocument::GetFile() in \Msdev\Mfc\Src\Doccore.cpp to see the default implementation.
• Create your own CMirrorFile class and check the return value of the GetFileSecurity() call. If the call fails, ignore the code that modifies the securities of the file. For example, you can create your own CMirrorFile-derived class like the following code demonstrates:

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#include <afxpriv.h>
#include "c:\msdev\mfc\src\afximpl.h"

class CMyMirrorFile: public CMirrorFile
{
      virtual BOOL Open(LPCTSTR lpszFileName, UINT nOpenFlags,
      CFileException* pError = NULL);
};

BOOL CMyMirrorFile::Open(LPCTSTR lpszFileName, UINT nOpenFlags,
      CFileException* pError)
{
    ASSERT(lpszFileName != NULL);
   m_strMirrorName.Empty();

#ifndef _MAC
   CFileStatus status;
   if (nOpenFlags & CFile::modeCreate) //opened for writing
   {
      if (CFile::GetStatus(lpszFileName, status))
      {
         CString strRoot;
         AfxGetRoot(lpszFileName, strRoot);

         DWORD dwSecPerClus, dwBytesPerSec, dwFreeClus, dwTotalClus;
         int nBytes = 0;
         if (GetDiskFreeSpace(strRoot, &dwSecPerClus, &dwBytesPerSec,
&dwFreeClus,
            &dwTotalClus))
         {
            nBytes = dwFreeClus*dwSecPerClus*dwBytesPerSec;
         }
         if (nBytes > 2*status.m_size) // at least 2x free space avail
         {
            // get the directory for the file
            TCHAR szPath[_MAX_PATH];
            LPTSTR lpszName;
            GetFullPathName(lpszFileName, _MAX_PATH, szPath, &lpszName);
            *lpszName = NULL;

            //let's create a temporary file name
            GetTempFileName(szPath, _T("MFC"), 0,
               m_strMirrorName.GetBuffer(_MAX_PATH+1));
            m_strMirrorName.ReleaseBuffer();
         }
      }
   }
#endif

   if (!m_strMirrorName.IsEmpty() &&
      CFile::Open(m_strMirrorName, nOpenFlags, pError))
   {
      m_strFileName = lpszFileName;
#ifndef _MAC
      FILETIME ftCreate, ftAccess, ftModify;
      if (::GetFileTime((HANDLE)m_hFile, &ftCreate, &ftAccess, &ftModify))
      {
         AfxTimeToFileTime(status.m_ctime, &ftCreate);
         SetFileTime((HANDLE)m_hFile, &ftCreate, &ftAccess, &ftModify);
      }

        // If GetFileSecurity returns an error, don't do anything with
        // file securities.
      DWORD dwLength = 0;
      PSECURITY_DESCRIPTOR pSecurityDescriptor = NULL;
      if (GetFileSecurity(lpszFileName, DACL_SECURITY_INFORMATION,
         NULL, dwLength, &dwLength))
        {
            pSecurityDescriptor = (PSECURITY_DESCRIPTOR) new
BYTE[dwLength];
          if (::GetFileSecurity(lpszFileName, DACL_SECURITY_INFORMATION,
             pSecurityDescriptor, dwLength, &dwLength))
          {
             SetFileSecurity(m_strMirrorName, DACL_SECURITY_INFORMATION,
pSecurityDescriptor);
          }
          delete[] (BYTE*)pSecurityDescriptor;
        }
#endif
      return TRUE;
   }
   m_strMirrorName.Empty();
   return CFile::Open(lpszFileName, nOpenFlags, pError);
}

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