FIX: Memory Leak when Requerying with a CTime Parameter |
Q115035
The information in this article applies to:
- The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++, version 1.5
SYMPTOMS
When running an MFC application that uses the database classes, the following message may appear in the Output Window of the debugger:
Detected memory leaks! Dumping objects -> {45}dbrfx.cpp(1331) : non-object block at $3FF74442, 16 bytes long Object dump complete.
The message only occurs when you select a date/time field of a table, use RFX_Date() to map a CTime variable to the field, and call Requery().
CAUSE
Line 1331 in DBRFX.CPP includes the following code:
// Allocate TIMESTAMP_STRUCT for SQLBindCol
pFX->m_prs->m_pvFieldProxy[nField-1] = new TIMESTAMP_STRUCT;
This line runs each time date/time fields are bound to CTime recordset variables using the RFX_Date() record field exchange function. When doing a Requery(), the fields of the result set must be rebound to the CRecordset's variables, and thus a Requery() causes the memory leak to occur. The line of code shown above assigns a new value to an element of a pointer array, leaving the previous allocation stranded in memory.
RESOLUTION
To resolve the memory leak, override the virtual Requery() function of CRecordset and delete the elements of the m_pvFieldProxy array. The following code demonstrates what to do:
BOOL CMyAppRecordSet::Requery()
{
// delete proxies for recordset fields
if (m_pvFieldProxy != NULL)
{
for (UINT nField = 0; nField != m_nFields; nField++)
delete m_pvFieldProxy[nField];
}
return CRecordset::Requery();
}
STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug was corrected in Visual C++ version 1.51.
Additional query words: ODBC 1.50 2.50
Keywords : kb16bitonly kbDatabase kbMFC kbODBC kbVC
Issue type :
Technology : kbAudDeveloper kbMFC
Last Reviewed: May 8, 2001 |
