Re: Is MFC reusing memory?

From:

"kalevet" <kalevet@gmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

12 Feb 2007 10:38:18 -0800

Message-ID:

<1171305498.648096.273010@l53g2000cwa.googlegroups.com>

Here goes... A bit lengthy, but will let you just copy and paste. I'm
using VC6, BTW.

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

void Test()
{
    LPCTSTR szLogFile = _T("C:\\HeapTest_d.log");

    LogHeap( szLogFile, _T("At the beginning of the test:") );
    {
        CStringArray stra;
        stra.SetSize(1000000);
        for (int n = 0; n < 1000000; ++n)
            stra[n] = _T("1234657890123465789012346578901234657890");
        LogHeap( szLogFile, _T("After CStringArray is built:") );
    }
    LogHeap( szLogFile, _T("After CStringArray is destructed:") );
}

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

bool LogHeap(LPCTSTR szFile, LPCTSTR szTitle)
{
    CFileException ex;
    CFile fLog;
    BOOL bRet;

    bRet = fLog.Open(szFile, CFile::modeCreate | CFile::modeNoTruncate
| CFile::modeWrite | CFile::shareDenyWrite, &ex);
    if ( ! bRet )
        return false;

    CString strTitle, strReport;
    strTitle.Format( _T("%s\r\n========================================
\r\n"), szTitle );
    strReport = MakeReport();

    fLog.SeekToEnd();
    fLog.Write( (LPCTSTR)strTitle, strTitle.GetLength() * sizeof
TCHAR );
    fLog.Write( (LPCTSTR)strReport, strReport.GetLength() * sizeof
TCHAR );

    return true;
}

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

CString MakeReport()
{
    _HEAPINFO hInfo;
    int nHeapStatus, nBlockSize;
    int nUsed[10], nFree[10], nUsedSize = 0, nFreeSize = 0;

    hInfo._pentry = NULL;
    ZeroMemory(nUsed, 40);
    ZeroMemory(nFree, 40);

    while ( ( nHeapStatus = _heapwalk(&hInfo) ) == _HEAPOK )
    {
        nBlockSize = (int)log10(hInfo._size);
        if (hInfo._useflag == _USEDENTRY)
        {
            ++nUsed[nBlockSize];
            nUsedSize += hInfo._size;
        }
        else
        {
            ++nFree[nBlockSize];
            nFreeSize += hInfo._size;
        }
    }

    CString strLine, strReport = _T("--- Used heap blocks found ---\r
\n");
    int nSize = 1, nTotal = 0;
    for (int n = 0; n < 10; ++n)
    {
        if ( nUsed[n] > 0 )
        {
            strLine.Format( _T("%ld blocks in size range %ld - %ld0\r
\n"), nUsed[n], nSize, nSize );
            strReport += strLine;
            nTotal += nUsed[n];
        }
        nSize *= 10;
    }
    strLine.Format( _T(">>> %ld bytes used, in %ld blocks.\r\n"),
nUsedSize, nTotal );
    strReport += strLine;
    nSize = 1;
    nTotal = 0;
    strReport += _T("--- Free heap blocks found ---\r\n");
    for (n = 0; n < 10; ++n)
    {
        if ( nUsed[n] > 0 )
        {
            strLine.Format( _T("%ld blocks in size range %ld - %ld0\r
\n"), nFree[n], nSize, nSize );
            strReport += strLine;
            nTotal += nFree[n];
        }
        nSize *= 10;
    }
    strLine.Format( _T(">>> %ld bytes used, in %ld blocks.\r\n"),
nFreeSize, nTotal );
    strReport += strLine;

    switch (nHeapStatus)
    {
    case _HEAPEMPTY:
        strReport += _T("Heap is empty!\r\n\r\n");
        break;
    case _HEAPEND:
        strReport += _T("Heap checked successfully.\r\n\r\n");
        break;
    case _HEAPBADPTR:
        strReport += _T("ERROR - bad pointer to heap!\r\n\r\n");
        break;
    case _HEAPBADBEGIN:
        strReport += _T("ERROR - bad start of heap!\r\n\r\n");
        break;
    case _HEAPBADNODE:
        strReport += _T("ERROR - bad node in heap!\r\n\r\n");
        break;
    }
    return strReport;
}